The Carboniferous (/ˌkɑːrbəˈnɪfərəs/KAHR-bə-NIF-ər-əs)[6] is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period 358.9 million years ago (Mya), to the beginning of the Permian Period, 298.9 million years ago. The name Carboniferous means "coal-bearing", from the Latincarbō ("coal") and ferō ("bear, carry"), and refers to the many coal beds formed globally during that time.[7]
In the packed field of prospective net-zero solutions, nuclear fusion
stands out in its scope and ambition. By successfully replicating the
reaction that powers the sun, humanity could—in the words of Stephen
Hawking—unlock an “inexhaustible supply of energy, without pollution or
global warming.” Fusion development has progressed at a glacial pace for
decades, however, and breakthroughs have been intermittent at best.
The law of superposition is an axiom that forms one of the bases of the sciences of geology, archaeology, and other fields pertaining to geological stratigraphy. In its plainest form, it states that in undeformed stratigraphic sequences, the oldest strata
will lie at the bottom of the sequence, while newer material stacks
upon the surface to form new deposits over time. This is paramount to stratigraphic dating,
which requires a set of assumptions, including that the law of
superposition holds true and that an object cannot be older than the
materials of which it is composed. To illustrate the practical
applications of superposition in scientific inquiry, sedimentary rock
that has not been deformed by more than 90° will exhibit the oldest
layers on the bottom, thus enabling paleontologists and paleobotanists
to identify the relative ages of any fossils found within the strata,
with the remains of the most archaic lifeforms confined to the lowest.
These findings can inform the community on the fossil record covering
the relevant strata, to determine which species coexisted temporally and
which species existed successively in perhaps an evolutionarily or phylogenetically relevant way.
The law of included fragments is a method of relative dating in geology. Essentially, this law states that clasts in a rock are older than the rock itself.[1] One example of this is a xenolith, which is a fragment of country rock that fell into passing magma as a result of stoping. Another example is a derived fossil, which is a fossil that has been eroded from an older bed and redeposited into a younger one.[2]
Mass wasting, also known as mass movement,[1] is a general term for the movement of rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is not entrained in a moving medium, such as water, wind, or ice. Types of mass wasting include creep, solifluction, rockfalls, debris flows, and landslides,
each with its own characteristic features, and taking place over
timescales from seconds to hundreds of years. Mass wasting occurs on
both terrestrial and submarine slopes, and has been observed on Earth, Mars, Venus, Jupiter's moons Io, and on many other bodies in the Solar System.
Salt tectonics, or halokinesis, or halotectonics, is concerned with the geometries and processes associated with the presence of significant thicknesses of evaporites containing rock salt within a stratigraphic sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength.
Salt structures (excluding undeformed layers of salt) have been found in more than 120 sedimentary basins around the world.[1]
Magnetostratigraphy
is a chronostratigraphic technique used to date sedimentary and
volcanic sequences. The method works by collecting oriented samples at
measured intervals throughout a section. The samples are analyzed to
determine their detrital remanent
magnetism (DRM), that is, the polarity of Earth's magnetic field at the
time a stratum was deposited. For sedimentary rocks this is possible
because, as they fall through the water column, very fine-grained
magnetic minerals (< 17 μm) behave like tiny compasses, orienting themselves with Earth's magnetic field.
Upon burial, that orientation is preserved. For volcanic rocks,
magnetic minerals, which form in the melt, orient themselves with the
ambient magnetic field, and are fixed in place upon crystallization of
the lava.
Oriented paleomagnetic core samples are collected in the field; mudstones, siltstones, and very fine-grained sandstones
are the preferred lithologies because the magnetic grains are finer and
more likely to orient with the ambient field during deposition. If the
ancient magnetic field were oriented similar to today's field (North Magnetic Pole near the North Rotational Pole), the strata would retain a normal polarity. If the data indicate that the North Magnetic Pole were near the South Rotational Pole, the strata would exhibit reversed polarity.
Results of the individual samples are analyzed by removing the natural remanent magnetization
(NRM) to reveal the DRM. Following statistical analysis, the results
are used to generate a local magnetostratigraphic column that can then
be compared against the Global Magnetic Polarity Time Scale.
This technique is used to date sequences that generally lack
fossils or interbedded igneous rocks. The continuous nature of the
sampling means that it is also a powerful technique for the estimation
of sediment-accumulation rates.
Chalk layers in Cyprus, showing sedimentary layering
Variation in rock units, most obviously displayed as visible layering, is due to physical contrasts in rock type (lithology). This variation can occur vertically as layering (bedding), or laterally, and reflects changes in environments of deposition (known as facies
change). These variations provide a lithostratigraphy or lithologic
stratigraphy of the rock unit. Key concepts in stratigraphy involve
understanding how certain geometric relationships between rock layers
arise and what these geometries imply about their original depositional
environment. The basic concept in stratigraphy, called the law of superposition, states: in an undeformed stratigraphic sequence, the oldest strata occur at the base of the sequence.
Chemostratigraphy studies the changes in the relative proportions of trace elements and isotopes within and between lithologic units. Carbon and oxygenisotope ratios
vary with time, and researchers can use those to map subtle changes
that occurred in the paleoenvironment. This has led to the specialized
field of isotopic stratigraphy.
Cyclostratigraphy documents the often cyclic changes in the relative proportions of minerals (particularly carbonates), grain size, thickness of sediment layers (varves) and fossil diversity with time, related to seasonal or longer term changes in palaeoclimates.
Biostratigraphy or paleontologic stratigraphy is based on fossil
evidence in the rock layers. Strata from widespread locations
containing the same fossil fauna and flora are said to be correlatable
in time. Biologic stratigraphy was based on William Smith's principle of faunal succession, which predated, and was one of the first and most powerful lines of evidence for, biological evolution. It provides strong evidence for the formation (speciation) and extinction of species. The geologic time scale
was developed during the 19th century, based on the evidence of
biologic stratigraphy and faunal succession. This timescale remained a
relative scale until the development of radiometric dating, which was based on an absolute time framework, leading to the development of chronostratigraphy.
One important development is the Vail curve,
which attempts to define a global historical sea-level curve according
to inferences from worldwide stratigraphic patterns. Stratigraphy is
also commonly used to delineate the nature and extent of hydrocarbon-bearing reservoir rocks, seals, and traps of petroleum geology.
Chronostratigraphy is the branch of stratigraphy that places an absolute age, rather than a relative age on rock strata. The branch is concerned with deriving geochronological
data for rock units, both directly and inferentially, so that a
sequence of time-relative events that created the rocks formation can be
derived. The ultimate aim of chronostratigraphy is to place dates on
the sequence of deposition of all rocks within a geological region, and
then to every region, and by extension to provide an entire geologic
record of the Earth.
A gap or missing strata in the geological record of an area is
called a stratigraphic hiatus. This may be the result of a halt in the
deposition of sediment. Alternatively, the gap may be due to removal by
erosion, in which case it may be called a stratigraphic vacuity.[2][3] It is called a hiatus because deposition was on hold for a period of time.[4] A physical gap may represent both a period of non-deposition and a period of erosion.[3] A geologic fault may cause the appearance of a hiatus.[5]
https://en.wikipedia.org/wiki/Stratigraphy
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists)
to describe the timing and relationships of events in geologic history.
The time scale has been developed through the study of rock layers and
the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardized international units of geologic time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective[1] is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC)[2]
that are used to define divisions of geologic time. The
chronostratigraphic divisions are in turn used to define geochronologic
units.[2]
While some regional terms are still in use,[3] the table of geologic time presented in this article conforms to the nomenclature, ages, and color codes set forth by the ICS as this is the standard, reference global geologic time scale – the International Geological Time Scale.[1][4]
https://en.wikipedia.org/wiki/Geologic_time_scale
https://en.wikipedia.org/wiki/Petroleum_geology
https://en.wikipedia.org/wiki/Paleomagnetism
https://en.wikipedia.org/wiki/Magnetostratigraphy
https://en.wikipedia.org/wiki/Siltstone
https://en.wikipedia.org/wiki/Mudstone
https://en.wikipedia.org/wiki/Sandstone
In geology, an assise (from the French, derived from Latinassidere, "to sit beside") is two or more beds or strata of rock united by the occurrence of the same characteristic species or genera.[1] In the hierarchy of stratigraphic units, an assise lies between a stage (or sub-stage) and a stratum.[2]
Ammonites are excellent index fossils, and linking the rock layer in which a particular species or genus is found to specific geologic time periods is often possible. Their fossil shells usually take the form of planispirals, although some helically spiraled and nonspiraled forms (known as heteromorphs) have been found.
The name "ammonite", from which the scientific term is derived,
was inspired by the spiral shape of their fossilized shells, which
somewhat resemble tightly coiled rams' horns. Pliny the Elder (d. 79 AD near Pompeii) called fossils of these animals ammonis cornua ("horns of Ammon") because the Egyptian god Ammon (Amun) was typically depicted wearing rams' horns.[2] Often, the name of an ammonite genus ends in -ceras, which is from κέρας (kéras) meaning "horn".
Filter feeders are a sub-group of suspension feeding animals
that feed by straining suspended matter and food particles from water,
typically by passing the water over a specialized filtering structure.
Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish (including some sharks). Some birds, such as flamingos and certain species of duck, are also filter feeders. Filter feeders can play an important role in clarifying water, and are therefore considered ecosystem engineers. They are also important in bioaccumulation and, as a result, as indicator organisms.
https://en.wikipedia.org/wiki/Filter_feeder
Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism.[1]
Bioaccumulation occurs when an organism absorbs a substance at a rate
faster than that at which the substance is lost or eliminated by catabolism and excretion. Thus, the longer the biological half-life of a toxic substance, the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high.[2] Bioaccumulation, for example in fish, can be predicted by models.[3][4] Hypothesis for molecular size cutoff criteria for use as bioaccumulation potential indicators are not supported by data.[5]Biotransformation can strongly modify bioaccumulation of chemicals in an organism.[6]
Toxicity induced by metals is associated with bioaccumulation and biomagnification.[7]
Storage or uptake of metals faster than the rate at which an organism
metabolizes and excretes lead to the accumulation of that metal.[8]
The presence of various chemicals and harmful substances in the
environment can be analyzed and assessed with a proper knowledge on
bioaccumulation helping with chemical control and usage.[9]
Uptake of chemicals by an organism can take place by breathing, absorbing through skin or swallowing.[7]
When the concentration of a chemical is higher within the organism
compared to its surroundings (air or water), it is referred to as bioconcentration.[1]
Biomagnification is another process related to bioaccumulation as the
concentration of the chemical or metal increases as it moves up from one
trophic level to another.[1]
Naturally, the process of bioaccumulation is necessary for an organism
to grow and develop; however, accumulation of harmful substances can
also occur.[7]
https://en.wikipedia.org/wiki/Bioaccumulation
Biomagnification, also known as bioamplification or biological magnification, is any concentration of a toxin, such as pesticides, in the tissues of tolerant organisms at successively higher levels in a food chain.[1] This increase can occur as a result of:
Persistence – where the substance cannot be broken down by environmental processes
Food chainenergetics – where the substance's concentration increases progressively as it moves up a food chain
Low or non-existent rate of internal degradation or excretion of the substance – mainly due to water-insolubility
Biomagnification
is the build up of toxins in a food chain. The DDT concentration is in
parts per million. As the trophic level increases in a food chain, the
amount of toxic build up increases. The x's represent the amount of
toxic build up accumulating as the trophic level increases. Toxins build
up in organism's fat and tissue. Predators accumulate higher toxins
than prey.
Biological magnification often refers to the process whereby certain
substances such as pesticides or heavy metals work their way into lakes,
rivers and the ocean, and then move up the food chain in progressively
greater concentrations as they are incorporated into the diet of aquatic
organisms such as zooplankton,
which in turn are eaten perhaps by fish, which then may be eaten by
bigger fish, large birds, animals, or humans. The substances become
increasingly concentrated in tissues or internal organs as they move up
the chain. Bioaccumulants are substances that increase in concentration
in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted.
https://en.wikipedia.org/wiki/Biomagnification
Toxaphene was an insecticide used primarily for cotton in the southern United States during the late 1960s and the 1970s.[3][4] Toxaphene is a mixture of over 670 different chemicals and is produced by reacting chlorine gas with camphene.[3][5] It can be most commonly found as a yellow to amber waxy solid.[3]
Testing performed on animals, mostly rats and mice, has demonstrated that toxaphene is harmful to animals. Exposure to toxaphene has proven to stimulate the central nervous system, as well as induce morphological changes in the thyroid, liver, and kidneys.[8]
Toxaphene has been shown to cause adverse health effects in humans. The main sources of exposure are through food, drinking water,
breathing contaminated air, and direct contact with contaminated soil.
Exposure to high levels of toxaphene can cause damage to the lungs, nervous system, liver, kidneys, and in extreme cases, may even cause death. It is thought to be a potential carcinogen in humans, though this has not yet been proven.[3]
Benzo[a]pyrene (BaP or B[a]P) is a polycyclic aromatic hydrocarbon and the result of incomplete combustion of organic matter
at temperatures between 300 °C (572 °F) and 600 °C (1,112 °F). The
ubiquitous compound can be found in coal tar, tobacco smoke and many
foods, especially grilled meats. The substance with the formula C20H12 is one of the benzopyrenes, formed by a benzene ring fused to pyrene. Its diol epoxide metabolites (more commonly known as BPDE) react with and bind to DNA, resulting in mutations and eventually cancer. It is listed as a Group 1 carcinogen by the IARC. In the 18th century a scrotal cancer of chimney sweepers, the chimney sweeps' carcinoma, was already known to be connected to soot.
https://en.wikipedia.org/wiki/Benzo(a)pyrene
Immune system
BaP has an effect on the number of white blood cells, inhibiting some of them from differentiating into macrophages,
the body's first line of defense to fight infections. In 2016, the
molecular mechanism was uncovered as damage to the macrophage membrane's
lipid raft integrity by decreasing membrane cholesterol at 25%. This
means less immunoreceptors CD32 (a member of the Fc family of
immunoreceptors) could bind to IgG and turn the white blood cell into a
macrophage. Therefore, macrophage membranes become susceptible to
bacterial infections.[14]
https://en.wikipedia.org/wiki/Benzo(a)pyrene
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil.[1]
Concretions are often ovoid or spherical in shape, although irregular
shapes also occur. The word 'concretion' is derived from the Latinconcretio "(act of) compacting, condensing, congealing, uniting", itself from con meaning 'together' and crescere meaning "to grow".[2] Concretions form within layers of sedimentary strata
that have already been deposited. They usually form early in the burial
history of the sediment, before the rest of the sediment is hardened
into rock. This concretionary cement often makes the concretion harder
and more resistant to weathering than the host stratum.
There is an important distinction to draw between concretions and nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body.
Descriptions dating from the 18th century attest to the fact that
concretions have long been regarded as geological curiosities. Because
of the variety of unusual shapes, sizes and compositions, concretions
have been interpreted to be dinosaur eggs, animal and plant fossils (called pseudofossils), extraterrestrial debris or human artifacts.
Telluric iron, also called native iron, is iron that originated on Earth, and is found in a metallic form rather than as an ore. Telluric iron is extremely rare, with only one known major deposit in the world, located in Greenland.
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metalmines or coal mines.
Acid rock drainage occurs naturally within some environments as
part of the rock weathering process but is exacerbated by large-scale
earth disturbances characteristic of mining and other large construction
activities, usually within rocks containing an abundance of sulfide minerals.
Areas where the earth has been disturbed (e.g. construction sites,
subdivisions, and transportation corridors) may create acid rock
drainage. In many localities, the liquid that drains from coal stocks, coal handling facilities, coal washeries, and coal wastetips
can be highly acidic, and in such cases it is treated as acid rock
drainage. This liquid often contains highly toxic metals, such as copper
or iron. These, combined with reduced pH, have a detrimental impact on
the streams aquatic environments.
Rio Tinto in Spain presents an acid drainage of both natural and artificial origin (mining)
Nomenclature
Historically,
the acidic discharges from active or abandoned mines were called acid
mine drainage, or AMD. The term acid rock drainage, or ARD, was
introduced in the 1980s and 1990s to indicate that acidic drainage can
originate from sources other than mines.[1]
For example, a paper presented in 1991 at a major international
conference on this subject was titled: "The Prediction of Acid Rock
Drainage – Lessons from the Database".[2] Both AMD and ARD refer to low pH or acidic waters caused by the oxidation of sulfide minerals, though ARD is the more generic name.
In cases where drainage from a mine is not acidic and has dissolved metals or metalloids, or was originally acidic, but has been neutralized along its flow path, then it is described as "neutral mine drainage",[3] "mining-influenced water"[4] or otherwise. None of these other names have gained general acceptance.
Occurrence
In
this case, the pyrite has dissolved away yielding a cube shape and
residual gold. This break down is the main driver of acid mine drainage.
Sub-surface mining often progresses below the water table,
so water must be constantly pumped out of the mine in order to prevent
flooding. When a mine is abandoned, the pumping ceases, and water floods
the mine. This introduction of water is the initial step in most acid
rock drainage situations. Tailings piles or ponds, mine waste rock dumps,[3] and coal spoils are also an important source of acid mine drainage.
After being exposed to air and water, oxidation of metal sulfides (often pyrite, which is iron-sulfide) within the surrounding rock and overburden generates acidity. Colonies of bacteria and archaea greatly accelerate the decomposition of metal ions, although the reactions also occur in an abiotic environment. These microbes, called extremophiles for their ability to survive in harsh conditions, occur naturally in the rock, but limited water and oxygen supplies usually keep their numbers low. Extremophiles known as acidophiles especially favor the low pH levels of abandoned mines. In particular, Acidithiobacillus ferrooxidans is a key contributor to pyrite oxidation.[5]
Metal mines may generate highly acidic discharges where the ore is a sulfide mineral or is associated with pyrite. In these cases the predominant metal ion may not be iron but rather zinc, copper, or nickel. The most commonly mined ore of copper, chalcopyrite, is itself a copper-iron-sulfide and occurs with a range of other sulfides. Thus, copper mines are often major culprits of acid mine drainage.
At some mines, acidic drainage is detected within 2–5 years after
mining begins, whereas at other mines, it is not detected for several
decades.[citation needed]
In addition, acidic drainage may be generated for decades or centuries
after it is first detected. For this reason, acid mine drainage is
considered a serious long-term environmental problem associated with
mining.[citation needed]
The chemistry of oxidation of pyrites, the production of ferrous ions and subsequently ferric ions, is very complex, and this complexity has considerably inhibited the design of effective treatment options.[6]
Although a host of chemical processes contribute to acid mine
drainage, pyrite oxidation is by far the greatest contributor. A general
equation for this process is:
The oxidation of the sulfide to sulfate solubilizes the ferrous iron (iron(II)), which is subsequently oxidized to ferric iron (iron(III)):
.
Either of these reactions can occur spontaneously or can be catalyzed
by microorganisms that derive energy from the oxidation reaction. The
ferric cations produced can also oxidize additional pyrite and reduce
into ferrous ions:
.
The net effect of these reactions is to release H+, which lowers the pH and maintains the solubility of the ferric ion.
Effects
Effects on pH
Yellow boy in a stream receiving acid drainage from surface coal mining
Water temperatures as high as 47 °C (117 °F)[8] have been measured underground at the Iron Mountain Mine, and the pH can be as low as −3.6.[9]
Organisms which cause acid mine drainage can thrive in waters with pH very close to zero. Negative pH[10] occurs when water evaporates from already acidic pools thereby increasing the concentration of hydrogen ions.
Acid rock drainage was a hindrance to the completion of the construction of Interstate 99 near State College, Pennsylvania.
However, this acid rock drainage didn't come from a mine; rather, it
was produced by oxidation of pyrite-rich rock which was unearthed during
a road cut and then used as filler material in the I-99 construction.[citation needed] Similar issues with pyritic slate occurred at the Halifax Stanfield International Airport in Canada.[12] When the phenomena is the result of earth-moving operations other than mining it is sometimes called "acid rock drainage".[citation needed]
Yellow boy
When the pH of acid mine drainage is raised past 3, either through contact with fresh water or neutralizing minerals, previously soluble iron(III) ions precipitate as iron(III) hydroxide, a yellow-orange solid colloquially known as yellow boy.[13] Other types of iron precipitates are possible, including iron oxides and oxyhydroxides, and sulfates such as jarosite. All these precipitates can discolor water and smother plant and animal life on the streambed, disrupting streamecosystems
(a specific offense under the Fisheries Act in Canada). The process
also produces additional hydrogen ions, which can further decrease pH.
In some cases, the concentrations of iron hydroxides in yellow boy are
so high, the precipitate can be recovered for commercial use in
pigments.[14]
Trace metal and semi-metal contamination
Many
acid rock discharges also contain elevated levels of potentially toxic
metals, especially nickel and copper with lower levels of a range of
trace and semi-metal ions such as lead, arsenic, aluminium, and manganese.
The elevated levels of heavy metals can only be dissolved in waters
that have a low pH, as is found in the acidic waters produced by pyrite
oxidation. In the coal belt around the south Wales valleys in the UK highly acidic nickel-rich discharges from coal stocking sites have proved to be particularly troublesome.[citation needed]
Effects on aquatic wildlife
Acid
mine drainage also affects the wildlife living within the affected body
of water. Aquatic macroinvertebrates living in streams or parts of
streams affected by acid mine drainage show fewer individuals, less
diversity, and lower biomass. Many species of fish also cannot tolerate
the pollution.[15]
Among the macroinvertebrates, certain species can be found at only
certain levels of pollution, while other species can be found over a
wide range.[16]
Identification and prediction
In
a mining setting it is leading practice to carry out a geochemical
assessment of mine materials during the early stages of a project to
determine the potential for AMD. The geochemical assessment aims to map
the distribution and variability of key geochemical parameters, acid
generating and element leaching characteristics.[17]
Modelling of oxidation, pollutant generation and release; and
Modelling of material composition.
Treatment
Oversight
In the United Kingdom, many discharges from abandoned mines are exempt from regulatory control. In such cases the Environment Agency working with partners such as the Coal Authority have provided some innovative solutions, including constructed wetland solutions such as on the River Pelenna in the valley of the River Afan near Port Talbot and the constructed wetland next to the River Neath at Ynysarwed.
Although abandoned underground mines produce most of the acid
mine drainage, some recently mined and reclaimed surface mines have
produced ARD and have degraded local ground-water and surface-water
resources. Acidic water produced at active mines must be neutralized to
achieve pH 6–9 before discharge from a mine site to a stream is
permitted.
In Canada, work to reduce the effects of acid mine drainage is
concentrated under the Mine Environment Neutral Drainage (MEND) program.
Total liability from acid rock drainage is estimated to be between $2
billion and C$5 billion.[19]
Over a period of eight years, MEND claims to have reduced ARD
liability by up to C$400 million, from an investment of C$17.5 million.[20]
Methods
Lime neutralization
By far, the most commonly used commercial process for treating acid mine drainage is lime (CaO)
precipitation in a high-density sludge (HDS) process. In this
application, a slurry of lime is dispersed into a tank containing acid
mine drainage and recycled sludge to increase water pH to about 9. At
this pH, most toxic metals become insoluble and precipitate, aided by
the presence of recycled sludge. Optionally, air may be introduced in
this tank to oxidize iron and manganese and assist in their
precipitation. The resulting slurry is directed to a sludge-settling
vessel, such as a clarifier.
In that vessel, clean water will overflow for release, whereas settled
metal precipitates (sludge) will be recycled to the acid mine drainage
treatment tank, with a sludge-wasting side stream. A number of
variations of this process exist, as dictated by the chemistry of ARD,
its volume, and other factors.[21] Generally, the products of the HDS process also contain gypsum (CaSO4)
and unreacted lime, which enhance both its settleability and resistance
to re-acidification and metal mobilization. A general equation for this
process is:
Less complex variants of this process, such as simple lime
neutralization, may involve no more than a lime silo, mixing tank and
settling pond. These systems are far less costly to build, but are also
less efficient (longer reaction times are required, and they produce a
discharge with higher trace metal concentrations, if present). They
would be suitable for relatively small flows or less complex acid mine
drainage.[22]
Calcium silicate neutralization
A
calcium silicate feedstock, made from processed steel slag, can also be
used to neutralize active acidity in AMD systems by removing free
hydrogen ions from the bulk solution, thereby increasing pH. As the
silicate anion captures H+ ions (raising the pH), it forms monosilicic acid (H4SiO4),
a neutral solute. Monosilicic acid remains in the bulk solution to play
many roles in correcting the adverse effects of acidic conditions. In
the bulk solution, the silicate anion is very active in neutralizing H+ cations in the soil solution.[23]
While its mode-of-action is quite different from limestone, the ability
of calcium silicate to neutralize acid solutions is equivalent to
limestone as evidenced by its CCE value of 90–100% and its relative
neutralizing value of 98%.[24]
In the presence of heavy metals, calcium silicate reacts in a
different manner than limestone. As limestone raises the pH of the bulk
solution, and if heavy metals are present, precipitation of the metal
hydroxides (with extremely low solubilities) is normally accelerated and
the potential of armoring of limestone particles increases
significantly.[25] In the calcium silicate aggregate,
as silicic acid species are absorbed onto the metal surface, the
development of silica layers (mono- and bi-layers) lead to the formation
of colloidal complexes with neutral or negative surface charges. These
negatively charged colloids create an electrostatic repulsion with each
other (as well as with the negatively charged calcium silicate granules)
and the sequestered metal colloids are stabilized and remain in a
dispersed state – effectively interrupting metal precipitation and
reducing vulnerability of the material to armoring.[23]
Carbonate neutralization
Generally, limestone or other calcareousstrata
that could neutralize acid are lacking or deficient at sites that
produce acidic rock drainage. Limestone chips may be introduced into
sites to create a neutralizing effect. Where limestone has been used,
such as at Cwm Rheidol in mid Wales, the positive impact has been much less than anticipated because of the creation of an insoluble calcium sulfate layer on the limestone chips, binding the material and preventing further neutralization.
Ion exchange
Cation exchange
processes have previously been investigated as a potential treatment
for acid mine drainage. The principle is that an ion exchange resin can
remove potentially toxic metals (cationic resins), or chlorides,
sulfates and uranyl sulfate complexes (anionic resins) from mine water.[26]
Once the contaminants are adsorbed, the exchange sites on resins must
be regenerated, which typically requires acidic and basic reagents and
generates a brine that contains the pollutants in a concentrated form. A
South African company that won the 2013 IChemE (ww.icheme.org) award
for water management and supply (treating AMD) have developed a patented
ion-exchange process that treats mine effluents (and AMD) economically.
Constructed wetlands
Constructed wetlands
systems have been proposed during the 1980s to treat acid mine drainage
generated by the abandoned coal mines in Eastern Appalachia.[27]
Generally, the wetlands receive near-neutral water, after it has been
neutralized by (typically) a limestone-based treatment process.[28]
Metal precipitation occurs from their oxidation at near-neutral pH,
complexation with organic matter, precipitation as carbonates or
sulfides. The latter results from sediment-borne anaerobic bacteria
capable of reverting sulfate ions into sulfide ions. These sulfide ions
can then bind with heavy metal ions, precipitating heavy metals out of
solution and effectively reversing the entire process.[citation needed]
The attractiveness of a constructed wetlands solution lies in its
relative low cost. They are limited by the metal loads they can deal
with (either from high flows or metal concentrations), though current
practitioners have succeeded in developing constructed wetlands that
treat high volumes (see description of Campbell Mine constructed wetland)
and/or highly acidic water (with adequate pre-treatment). Typically,
the effluent from constructed wetland receiving near-neutral water will
be well-buffered at 6.5–7.0 and can readily be discharged. Some of metal
precipitates retained in sediments are unstable when exposed to oxygen
(e.g., copper sulfide or elemental selenium), and it is very important
that the wetland sediments remain largely or permanently submerged.
An example of an effective constructed wetland is on the Afon Pelena in the River Afan valley above Port Talbot where highly ferruginous discharges from the Whitworth mine have been successfully treated.
Precipitation of metal sulfides
Most base metals in acidic solution precipitate in contact with free sulfide, e.g. from H2S
or NaHS. Solid-liquid separation after reaction would produce a base
metal-free effluent that can be discharged or further treated to reduce
sulfate, and a metal sulfide concentrate with possible economic value.
As an alternative, several researchers have investigated the precipitation of metals using biogenic sulfide. In this process, Sulfate-reducing bacteria oxidize organic matter using sulfate, instead of oxygen. Their metabolic products include bicarbonate, which can neutralize water acidity, and hydrogen sulfide,
which forms highly insoluble precipitates with many toxic metals.
Although promising, this process has been slow in being adopted for a
variety of technical reasons.[29]
Technologies
Many technologies exist for the treatment of AMD from traditional high cost water treatment plants to simple in situ water treatment reagent dosing methods.
Scientists have recently begun to explore acid mine drainage and mine reclamation
sites for unique soil bacteria capable of producing new pharmaceutical
leads. Soil microbes have long been a source for effective drugs[32] and new research, such as that conducted at the Center for Pharmaceutical Research and Innovation, suggests these extreme environments to be an untapped source for new discovery.[33][34]
List of selected acid mine drainage sites worldwide
This
list includes both mines producing acid mine drainage and river systems
significantly affected by such drainage. It is by no means complete, as
worldwide, several thousands of such sites exist.
https://en.wikipedia.org/wiki/Acid_mine_drainage
Uranium acid mine drainage refers to acidic water released from a uranium mining site using processes like underground mining and in-situ leaching.[1] Underground, the ores are not as reactive due to isolation from atmospheric oxygen
and water. When uranium ores are mined, the ores are crushed into a
powdery substance, thus increasing surface area to easily extract
uranium. The ores, along with nearby rocks, may also contain sulfides.
Once exposed to the atmosphere, the powdered tailings react with
atmospheric oxygen and water. After uranium extraction, sulfide minerals
in uranium tailings facilitates the release of uranium radionuclides into the environment, which can undergo further radioactive decay while lowering the pH of a solution.[2]
Uranium-238 Decay Chain
Uranium chemistry
Uranium may exist naturally as U+6 in ores but also forms the water-soluble uranyl ion UO2+2 when uranium tailings are oxidized by atmospheric oxygen in the following reaction.[2]
U+6 + O2 → UO2+2
The solubility of uranium increases under similar oxidizing conditions when it forms uranyl carbonate complexes in the following reaction.[2]
U+6 + O2 + 2CO32−→ [UO2(CO3)2]2+
Extraction of uranium from the ore may occur under acid or alkaline leaching processes using sulfuric acid and sodium carbonate respectively. If leached with sulfuric acid, uranyl forms a soluble uranyl sulfate complex in the following reaction.[2]Hydrogen ions in solution react with water to produce hydronium ions which lowers a solution's pH making it more acidic.
UO2 + 3H2SO4 + 1/2 O2 → [UO2(SO4)3]4− + H2O + 4H+
H+(aq) + H2O(l) → H3O+(aq)
During in-situ leaching uranyl reacts with iron, a common natural oxidant, to produce uranyl trioxide which is further oxidized then leached using alkaline sodium carbonate in the following reactions.[2]
When considering the formation secondary uranium minerals, as
discussed in the case study section below, the pH of the solution that
contains uranophane
is one of determining factors of how much of the uranophane is in
mineral form or in the form of its ions. Shown in figure 2, from a study
performed by Tatiana Shvareva et al. in 2011, is the dissolution of
uranophane in pH of 3 (Figure 3b) and pH of 4 (Figure 3a). The graphs
demonstrate that in a more acidic environment, the concentrations of Ca, U, and Si are more likely to be more abundant in more basic environments where it is more likely that they will form minerals.[3]
This is more likely to happen when the acidic mine drainage is released
into rivers or large water deposits and they become diluted to a pH
closer to that of water.[4]
The enthalpies of formation (from elements and from oxide species) and Gibbs free energies of formation (from elements) of the uranium minerals boltwoodite,
Na-boltwoodite, and uranophane are shown in Table 1. Solubility
constants (dissociation of minerals to ions) of the same minerals,
determined using a bomb calorimeter
in a study by Shvareva, Tatiana et al. in 2011, are shown in Table 2.
The Gibbs free energies of formation show that the process, when the
reactions from the individual elements to the oxides are taken into
account, is spontaneous. The enthalpies of formation, when only
considering the reaction from the oxides to the mineral, suggest a
relatively high probability for their Gibbs free energy of formation
values to also be spontaneous.[3]
ΔHf, ox (kJ/mol)
ΔHf, el (kJ/mol)
ΔGf, el (kJ/mol)
Boltwoodite: K(UO2)(HSiO4):HO
-251.2 ± 5.9
-2766.8 ± 6.5
-2758.6 ± 3.5
Na-boltwoodite: Na(UO2)(HSiO4):H2O
-215.8 ± 6.0
-2948.8 ± 6.6
-2725.2 ± 2.6
Uranophane: ½[Ca(UO2)2(HSiO4):5H2O]
-161.1 ± 5.4
-3399.5 ± 5.8
-3099.3 ± 5.6
Table 1. The enthalpy of formation (from oxide to mineral), enthalpy
of formation (from individual elements to mineral), and Gibbs free
energy (from individual elements to mineral) of boltwoodite,
Na-boltwoodite, and uranophane.[3]
log Ksp ± 2σ
Mass action equations
Boltwoodite: K(UO2)(HSiO4):H2O
4.12 (-0.48/+0.30)
Ksp =
Na-boltwoodite: Na(UO2)(HSiO4):H2O
6.07 (-0.16/+0.26)
Ksp =
Uranophane: ½[Ca(UO2)2(HSiO4):5H2O]
10.82 (-0.62/+0.29)
Ksp =
Table 2. Solubility constants and mass action equations for boltwoodite, Na-boltwoodite, and uranophane.[3]
Uranium acid mine drainage case study
Two uranium mines in northern Portugal, Quinta do Bispo and Cunha Baixa,
have been inactive since 1991. Acidic water is pumped out of the mines
for neutralization and precipitation of radionuclides using calcium hydroxide.[5]
Studies in 2002 found that there were high concentrations of soluble
and suspended uranium radionuclides in river water samples near the
mines.[5] Castelo river reached suspended uranium isotope concentrations of -72 kBq/kg which is roughly 170x higher than normal concentrations in the Mondego River but returned to normal after 7 km.[5] The mine waters of Quinta do Bispo and Cunha Baixa had low pH values at 2.67 and 3.48 with U-238 concentrations of 92,000 mBq/L and 2,200 mBq/L, respectively.[5]
Results from studies done in 2002 showed a significant negative
correlation between both dissolved uranium radionuclides and hydrogen
ions with pH in mine waters.[5] Sorption of dissolved uranium radionuclides in rivers combine with nearby rock sediments can form minerals like uranophane.[5] The chemistry and findings in this case is essentially representative of other uranium mines in the world.
Uranium radionuclides in the environment
An
uranium radionuclide is a radioactive isotope. Radioactivity is natural
in the environment, however uranium radionuclides can lead to
radioactive decay. In the case of uranium mines, these radionuclides can
leach into the water and cause the radioactivity to be carried
elsewhere, as well as form precipitates that can be harmful to the
environment. The uranium radionuclides can eventually be carried to fruits and vegetables
via contaminated waters. Sulfuric acid, oxidation, and alkaline
leaching are processes of how radionuclides make their way into the
environment. When uranium decays it also produces the isotopes 226Ra and 222Rn, which may be environmentally harmful due to the fact that radon is present as an inert gas and therefore, might enter into the soil or atmosphere. Radon then can emit alpha particles and gamma radiation.[6] The three different radioactive isotopes of uranium are uranium-238, uranium-235, and uranium-234. Each has a different half-life which determines the isotope's decay rate.[7]
When uranium-235 combines with other molecules it creates a chemical
reaction that can cause detrimental effects to water. Even though
isotope formation occurs naturally, when combined with other elements it
can cause the pH of water to become more acidic as discussed
previously.[8]
Kvanefjeld (or Kuannersuit), in Greenland, is the site of a mineral deposit, which is claimed to be the world's second-largest deposit of rare-earth oxides, and the sixth-largest deposit of uranium.[1][2] There are also substantial sodium fluoride deposits, and Kvanefjeld is thought to be one of the largest multi-element deposits of its kind in the world.[3]
https://en.wikipedia.org/wiki/Kvanefjeld
Nepheline syenite is a holocrystallineplutonic rock that consists largely of nepheline and alkalifeldspar.[1] The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known. Phonolite is the fine-grained extrusive equivalent.
Aenigmatite, also known as Cossyrite after Cossyra, the ancient name of Pantelleria, is a sodium, iron, titaniuminosilicatemineral. The chemical formula is Na2Fe2+5TiSi6O20
and its structure consists of single tetrahedral chains with a repeat
unit of four and complex side branches. It forms brown to black triclinic lamellar crystals. It has Mohs hardness of 5.5 to 6 and specific gravity of 3.74 to 3.85. Aenigmatite forms a solid-solution series with wilkinsonite, Na2Fe2+4Fe3+2Si6O20.
Vauxite is a phosphate mineral with the chemical formula Fe2+Al2(PO4)2(OH)2·6(H2O). It belongs to the laueite – paravauxite group, paravauxite subgroup,[3][6] although Mindat puts it as a member of the vantasselite Al4(PO4)3(OH)3·9H2O group.[4] There is no similarity in structure between vauxite and paravauxite Fe2+Al2(PO4)2(OH)2·8H2O or metavauxite Fe3+Al2(PO4)2(OH)2·8H2O, even though they are closely similar chemically, and all minerals occur together as secondary minerals.[6] Vauxite was named in 1922 for George Vaux Junior (1863–1927), an American attorney and mineral collector.
Vauxite
Vauxite from the Siglio XX Mine, Llallagua, Bolivia. Specimen size 2 cm
In standard mineral classification systems (in both the Dana[1] and Strunz[2] systems) the phosphate class includes the arsenates, vanadates and the polyvanadates. Strunz includes the vanadates(V, VI) in the oxides class.
Subcategories
This category has the following 3 subcategories, out of 3 total.
subdivision of an age, not used by the ICS timescale
https://en.wikipedia.org/wiki/Eonothem
Antimatter-catalyzed nuclear pulse propulsion (also antiproton-catalyzed nuclear pulse propulsion) is a variation of nuclear pulse propulsion based upon the injection of antimatter into a mass of nuclear fuel to initiate a nuclear chain reaction for propulsion when the fuel does not normally have a critical mass.
Technically, the process is not a '"catalyzed'" reaction because anti-protons (antimatter) used to start the reaction are consumed; if they were present as a catalyst
the particles would be unchanged by the process and used to initiate
further reactions. Although antimatter particles may be produced by the
reaction itself, they are not used to initiate or sustain chain
reactions.[1][2]
Description
Typical nuclear pulse propulsion has the downside that the minimal size of the engine is defined by the minimal size of the nuclear bombs used to create thrust, which is a function of the amount of critical mass required to initiate the reaction. A conventional thermonuclear bomb design consists of two parts: the primary, which is almost always based on plutonium, and a secondary using fusion fuel, which is normally deuterium in the form of lithium deuteride,
and tritium (which is created during the reaction as lithium is
transmuted to tritium). There is a minimal size for the primary (about
10 kilograms for plutonium-239) to achieve critical mass. More powerful
devices scale up in size primarily through the addition of fusion fuel
for the secondary. Of the two, the fusion fuel is much less expensive
and gives off far fewer radioactive products, so from a cost and
efficiency standpoint, larger bombs are much more efficient. However,
using such large bombs for spacecraft propulsion demands much larger
structures able to handle the stress. There is a tradeoff between the
two demands.
By injecting a small amount of antimatter into a subcritical mass of fuel (typically plutonium or uranium) fission of the fuel can be forced. An anti-proton has a negative electric charge, just like an electron, and can be captured in a similar way by a positively charged atomic nucleus. The initial configuration, however, is not stable and radiates energy as gamma rays. As a consequence, the anti-proton moves closer and closer to the nucleus until their quarks can interact, at which point the anti-proton and a proton are both annihilated.
This reaction releases a tremendous amount of energy, of which some is
released as gamma rays and some is transferred as kinetic energy to the
nucleus, causing it to split (the fission reaction). The resulting
shower of neutrons can cause the surrounding fuel to undergo rapid fission or even nuclear fusion.
The lower limit of the device size is determined by anti-proton handling
issues and fission reaction requirements, such as the structure used to
contain and direct the blast. As such, unlike either the Project Orion-type
propulsion system, which requires large numbers of nuclear explosive
charges, or the various anti-matter drives, which require impossibly
expensive amounts of antimatter, antimatter-catalyzed nuclear pulse
propulsion has intrinsic advantages.[3]
A conceptual design of an antimatter-catalyzed thermonuclear explosive physics package is one in which the primary mass of plutonium usually necessary for the ignition in a conventional Teller–Ulam thermonuclear explosion, is replaced by one microgram
of antihydrogen. In this theoretical design, the antimatter is
helium-cooled and magnetically levitated in the center of the device, in
the form of a pellet a tenth of a millimeter in diameter, a position
analogous to the primary fission core in the layer cake/Sloika design.[4][5]
As the antimatter must remain away from ordinary matter until the
desired moment of the explosion, the central pellet must be isolated
from the surrounding hollow sphere of 100 grams of thermonuclear fuel.
During and after the implosive compression by the high-explosive lenses, the fusion fuel comes into contact with the antihydrogen. Annihilation reactions, which would start soon after the Penning trap
is destroyed, is to provide the energy to begin the nuclear fusion in
the thermonuclear fuel. If the chosen degree of compression is high, a
device with increased explosive/propulsive effects is obtained, and if
it is low, that is, the fuel is not at high density, a considerable
number of neutrons will escape the device, and a neutron bomb forms. In both cases the electromagnetic pulse effect and the radioactive fallout are substantially lower than that of a conventional fission or Teller–Ulam device of the same yield, approximately 1 kt.[6]
Amount needed for thermonuclear device
The number of antiprotons required for triggering one thermonuclear explosion were calculated in 2005 to be 1018, which means microgram amounts of antihydrogen.[7]
Tuning of the performance of a space vehicle is also possible. Rocket efficiency is strongly related to the mass of the working mass
used, which in this case is the nuclear fuel. The energy released by a
given mass of fusion fuel is several times larger than that released by
the same mass of a fission fuel. For missions requiring short periods of
high thrust, such as crewed interplanetary missions, pure microfission
might be preferred because it reduces the number of fuel elements
needed. For missions with longer periods of higher efficiency but with
lower thrust, such as outer-planet probes, a combination of microfission
and fusion might be preferred because it would reduce the total fuel
mass.
Research
The concept was invented at Pennsylvania State University before 1992. Since then, several groups have studied antimatter-catalyzed micro fission/fusion engines in the lab.[8] Work has been performed at Lawrence Livermore National Laboratory on antiproton-initiated fusion as early as 2004.[9] In contrast to the large mass, complexity and recirculating power of conventional drivers for inertial confinement fusion
(ICF), antiproton annihilation offers a specific energy of 90 MJ/µg and
thus a unique form of energy packaging and delivery. In principle,
antiproton drivers could provide a profound reduction in system mass for
advanced space propulsion by ICF.
Antiproton-driven ICF is a speculative concept, and the handling
of antiprotons and their required injection precision—temporally and
spatially—will present significant technical challenges. The storage and
manipulation of low-energy antiprotons, particularly in the form of antihydrogen,
is a science in its infancy, and a large scale-up of antiproton
production over present supply methods would be required to embark on a
serious R&D programme for such applications.
A record for antimatter storage of just over 1000 seconds, performed in the CERN facility, during 2011, was at the time a monumental leap from the millisecond timescales that previously were achievable.[10]
Total world-wide production of anti-protons in a period of a year
is in the range of nanograms. The anti-matter trap (Mark 1 version) at Penn State University has the capacity for the storage of 10 billion for a period of approximately 168 hours. Project Icarus has given the estimated potential cost of production of 1 milligram of anti-proton as $100 billion.[11]
An antimatter weapon is a theoretically possible device using antimatter as a power source, a propellant, or an explosive for a weapon.
Antimatter weapons are currently too costly and unreliable to be viable
in warfare, as producing antimatter is enormously expensive (estimated
at $6 billion for every 100 nanograms), the quantities of antimatter
generated are very small, and current technology has great difficulty
containing antimatter, which annihilates upon touching ordinary matter.[1]
The dodo became extinct during the mid-to-late 17th century due to habitat destruction, overhunting, and predation by introduced mammals.[1] It is an often-cited example of a modern extinction.[2]
During the past 100–200 years, biodiversity loss and species extinction have accelerated[10] to the point that most conservation biologists now believe that humankind has either entered a period of mass extinction,[14][15] or is on the cusp of doing so.[16][17] As such, the event has also been referred to as the sixth mass extinction or sixth extinction.[18]
The Holocene extinction includes the disappearance of large land animals known as megafauna, starting at the end of the last glacial period. Megafauna outside of the African mainland, which did not evolve alongside humans, proved highly sensitive to the introduction of human predation, and many died out shortly after early humans began spreading and hunting across the Earth.[19][20] Many African species have also gone extinct in the Holocene,
along with species in North America, South America, and Australia, but –
with some exceptions – the megafauna of the Eurasian mainland was
largely unaffected until a few hundred years ago.[21] These extinctions, occurring near the Pleistocene–Holocene boundary, are sometimes referred to as the Quaternary extinction event.
The most popular theory is that human overhunting of species added to existing stress conditions as the Holocene extinction coincides with human colonization of many new areas around the world. Although there is debate regarding how much human predation and habitat loss
affected their decline, certain population declines have been directly
correlated with the onset of human activity, such as the extinction
events of New Zealand and Hawaii. Aside from humans, climate change may have been a driving factor in the megafaunal extinctions, especially at the end of the Pleistocene.
There is no general agreement on where the Holocene, or anthropogenic, extinction begins, and the Quaternary extinction event, which includes climate change resulting in the end of the last ice age, ends, or if they should be considered separate events at all.[44][45] The Holocene extinction is mainly caused by human activities.[41][10][43][46]
Some have suggested that anthropogenic extinctions may have begun as
early as when the first modern humans spread out of Africa between
200,000 and 100,000 years ago; this is supported by rapid megafaunal
extinction following recent human colonisation in Australia, New Zealand and Madagascar.[42] In many cases, it is suggested that even minimal hunting pressure was enough to wipe out large fauna, particularly on geographically isolated islands.[47][48] Only during the most recent parts of the extinction have plants also suffered large losses.[49][better source needed]
Extinction rate
The contemporary rate of extinction of species is estimated at 100 to 1,000 times higher than the background extinction rate, the historically typical rate of extinction (in terms of the natural evolution of the planet);[11][12][50] also, the current rate of extinction is 10 to 100 times higher than in any of the previous mass extinctions in the history of Earth. One scientist estimates the current extinction rate may be 10,000 times the background extinction rate, although most scientists predict a much lower extinction rate than this outlying estimate.[51]Theoretical ecologistStuart Pimm stated that the extinction rate for plants is 100 times higher than normal.[52]
Some contend that contemporary extinction has yet to reach the level of the previous five mass extinctions,[53] and that this comparison downplays how severe the first five mass extinctions were.[54]
John Briggs argues that there is inadequate data to determine the real
rate of extinctions, and shows that estimates of current species
extinctions varies enormously, ranging from 1.5 species to 40,000
species going extinct due to human activities each year.[55] Both papers from Barnosky
et al. (2011) and Hull et al. (2015) point out that the real rate of
extinction during previous mass extinctions is unknown, both as only
some organisms leave fossil remains, and as the temporal resolution of
the fossil layer is larger than the time frame of the extinction events.[17][56] However, all these authors agree that there is a modern biodiversity crisis
with population declines affecting numerous species, and that a future
anthropogenic mass extinction event is a big risk. The 2011 study by
Barnosky et al. confirms that "current extinction rates are higher than
would be expected from the fossil record" and adds that anthropogenic
ecological stressors, including climate change, habitat fragmentation,
pollution, overfishing, overhunting, invasive species and expanding
human biomass will intensify and accelerate extinction rates in the future without significant mitigation efforts.[17]
In The Future of Life (2002), Edward Osborne Wilson of Harvard calculated that, if the current rate of human disruption of the biosphere continues, one-half of Earth's higher lifeforms will be extinct by 2100. A 1998 poll conducted by the American Museum of Natural History found that 70% of biologists acknowledge an ongoing anthropogenic extinction event.[57]
In a pair of studies published in 2015, extrapolation from
observed extinction of Hawaiian snails led to the conclusion that 7% of
all species on Earth may have been lost already.[58][59] A 2021 study published in the journal Frontiers in Forests and Global Change found that only around 3% of the planet's terrestrial surface is ecologically and faunally intact, meaning areas with healthy populations of native animal species and little to no human footprint.[60][61]
The 2019 Global Assessment Report on Biodiversity and Ecosystem Services, published by the United Nations' Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services
(IPBES), posits that roughly one million species of plants and animals
face extinction within decades as the result of human actions.[31][62][63][64]
Organized human existence is jeopardized by increasingly rapid
destruction of the systems that support life on Earth, according to the
report, the result of one of the most comprehensive studies of the
health of the planet ever conducted.[65] Moreover, the 2021 Economics of Biodiversity review, published by the UK government, asserts that "biodiversity is declining faster than at any time in human history."[66][67] According to a 2022 study published in Frontiers in Ecology and the Environment,
a survey of more than 3,000 experts says that the extent of the mass
extinction might be greater than previously thought, and estimates that
roughly 30% of species "have been globally threatened or driven extinct
since the year 1500."[68][69] In a 2022 report, IPBES listed unsustainable fishing, hunting and logging as being some of the primary drivers of the global extinction crisis.[70]
Attribution
We are currently, in a systematic manner, exterminating all non-human living beings.
There is widespread consensus among scientists that human activity is
accelerating the extinction of many animal species through the
destruction of habitats, the consumption of animals as resources, and
the elimination of species that humans view as threats or competitors.[46]
That humans have become the primary driver of modern extinctions is
undeniable, rising extinction trends impacting numerous animal groups
including mammals, birds, reptiles, and amphibians have prompted
scientists to declare a biodiversity crisis.[72]
Scientific debate
Characterisation of recent extinction as a mass extinction has been debated among scientists. Stuart Pimm, for example, asserts that the sixth mass extinction "is something that hasn't happened yet – we are on the edge of it."[73] Several studies posit that the earth has entered a sixth mass extinction event,[41][39][29][74] including a 2015 paper by Barnosky et al.[13] and a November 2017 statement titled "World Scientists’ Warning to Humanity: A Second Notice",
led by eight authors and signed by 15,364 scientists from 184 countries
which asserted that, among other things, "we have unleashed a mass
extinction event, the sixth in roughly 540 million years, wherein many
current life forms could be extirpated or at least committed to
extinction by the end of this century."[32] The World Wide Fund for Nature's 2020 Living Planet Report says that wildlife populations have declined by 68% since 1970 as a result of overconsumption, population growth and intensive farming,
which is further evidence that humans have unleashed a sixth mass
extinction event; however, this finding has been disputed by one 2020
study, which posits that this major decline was primarily driven by a
few extreme outlier populations, and that when these outliers are
removed, the trend shifts to that of a decline between the 1980s and
2000s, but a roughly positive trend after 2000.[75][76][77][78] A 2021 report in Frontiers in Conservation Science
which cites both of the aforementioned studies, says "population sizes
of vertebrate species that have been monitored across years have
declined by an average of 68% over the last five decades, with certain
population clusters in extreme decline, thus presaging the imminent
extinction of their species," and asserts "that we are already on the
path of a sixth major extinction is now scientifically undeniable."[79] A 2022 study published in Biological Reviews
builds upon previous studies documenting biodiversity decline to assert
that a sixth mass extinction event caused by anthropogenic activity is
currently underway.[80][81]
According to the UNDP's 2020 Human Development Report, The Next Frontier: Human Development and the Anthropocene:
The planet's biodiversity is
plunging, with a quarter of species facing extinction, many within
decades. Numerous experts believe we are living through, or on the cusp
of, a mass species extinction event, the sixth in the history of the
planet and the first to be caused by a single organism—us.[82]
The 2022 Living Planet Report found that vertebrate wildlife populations have plummeted by an average of almost 70% since 1970, with agriculture and fishing being the primary drivers of this decline.[83][84]
Some scientists, including Rodolfo Dirzo and Paul R. Ehrlich,
contend that the sixth mass extinction is largely unknown to most
people globally, and is also misunderstood by many in the scientific
community. They say it is not the disappearance of species, which gets
the most attention, that is at the heart of the crisis, but "the
existential threat of myriad population extinctions."[85]
A diagram showing the ecological processes of coral reefs before and during the Anthropocene
The abundance of species extinctions considered anthropogenic,
or due to human activity, has sometimes (especially when referring to
hypothesized future events) been collectively called the "Anthropocene
extinction".[46][86][87]Anthropocene is a term introduced in 2000.[88][89] Some now postulate that a new geological epoch has begun, with the most abrupt and widespread extinction of species since the Cretaceous–Paleogene extinction event 66 million years ago.[42]
The term "anthropocene" is being used more frequently by
scientists, and some commentators may refer to the current and projected
future extinctions as part of a longer Holocene extinction.[90][91]
The Holocene–Anthropocene boundary is contested, with some commentators
asserting significant human influence on climate for much of what is
normally regarded as the HoloceneEpoch.[92] Other commentators place the Holocene–Anthropocene boundary at the industrial revolution
and also say that "[f]ormal adoption of this term in the near future
will largely depend on its utility, particularly to earth scientists
working on late Holocene successions."
It has been suggested that human activity has made the period
starting from the mid-20th century different enough from the rest of the
Holocene to consider it a new geological epoch, known as the Anthropocene,[93][94] a term which was considered for inclusion in the timeline of Earth's history by the International Commission on Stratigraphy in 2016.[95][96] In order to constitute the Holocene as an extinction event, scientists must determine exactly when anthropogenic greenhouse gas emissions
began to measurably alter natural atmospheric levels on a global scale,
and when these alterations caused changes to global climate. Using
chemical proxies from Antarctic ice cores, researchers have estimated
the fluctuations of carbon dioxide (CO2) and methane (CH4) gases in the Earth's atmosphere during the late Pleistocene and Holocene epochs.[92]
Estimates of the fluctuations of these two gases in the atmosphere,
using chemical proxies from Antarctic ice cores, generally indicate that
the peak of the Anthropocene occurred within the previous two
centuries: typically beginning with the Industrial Revolution, when the highest greenhouse gas levels were recorded.[97][98]
A 2015 article in Science
suggested that humans are unique in ecology as an unprecedented "global
superpredator", regularly preying on large numbers of fully grown
terrestrial and marine apex predators, and with a great deal of influence over food webs and climatic systems worldwide.[26]
Although significant debate exists as to how much human predation and
indirect effects contributed to prehistoric extinctions, certain
population crashes have been directly correlated with human arrival.[20][42][45][46] Human activity has been the main cause of mammalian extinctions since the Late Pleistocene.[72] A 2018 study published in PNAS found that since the dawn of human civilization, the biomass
of wild mammals has decreased by 83%. The biomass decrease is 80% for
marine mammals, 50% for plants and 15% for fish. Currently, livestock
make up 60% of the biomass of all mammals on earth, followed by humans
(36%) and wild mammals (4%). As for birds, 70% are domesticated, such as
poultry, whereas only 30% are wild.[99][100]
The percentage of megafauna on different land masses over time, with the arrival of humans indicated.
Extinction of animals, plants, and other organisms caused by human actions may go as far back as the late Pleistocene, over 12,000 years ago.[46] There is a correlation between megafaunal extinction and the arrival of humans.[101][102][103] Over the past 125,000 years, the average body size of wildlife has fallen by 14% as human actions eradicated megafauna on all continents with the exception of Africa.[104]
Human civilization was founded on and grew from agriculture.[105] The more land used for farming, the greater the population a civilization could sustain,[92][105] and subsequent popularization of farming led to habitat conversion.[10]
Habitat destruction by humans, thus replacing the original local ecosystems, is a major driver of extinction.[106]
The sustained conversion of biodiversity rich forests and wetlands into
poorer fields and pastures (of lesser carrying capacity for wild
species), over the last 10,000 years, has considerably reduced the
Earth's carrying capacity for wild birds, among other organisms, in both
population size and species count.[107][108][109]
Recent investigations into the practice of landscape burning during the Neolithic Revolution
has a major implication for the current debate about the timing of the
Anthropocene and the role that humans may have played in the production
of greenhouse gases prior to the Industrial Revolution.[105] Studies of early hunter-gatherers raise questions about the current use of population size or density as a proxy for the amount of land clearance and anthropogenic burning that took place in pre-industrial times.[111][112] Scientists have questioned the correlation between population size and early territorial alterations.[112]
Ruddiman and Ellis' research paper in 2009 makes the case that early
farmers involved in systems of agriculture used more land per capita
than growers later in the Holocene, who intensified their labor to
produce more food per unit of area (thus, per laborer); arguing that
agricultural involvement in rice production implemented thousands of
years ago by relatively small populations have created significant
environmental impacts through large-scale means of deforestation.[105]
While a number of human-derived factors are recognized as contributing to rising atmospheric concentrations of CH4 (methane) and CO2
(carbon dioxide), deforestation and territorial clearance practices
associated with agricultural development may be contributing most to
these concentrations globally.[97][105][113] Scientists that are employing a variance of archaeological
and paleoecological data argue that the processes contributing to
substantial human modification of the environment spanned many thousands
of years on a global scale and thus, not originating as late as the Industrial Revolution. Gaining popularity on his uncommon hypothesis, palaeoclimatologist William Ruddiman
in 2003, has argued that in the early Holocene 11,000 years ago,
atmospheric carbon dioxide and methane levels fluctuated in a pattern
which was different from the Pleistocene epoch before it.[92][111][113] He argued that the patterns of the significant decline of CO2
levels during the last ice age of the Pleistocene inversely correlates
to the Holocene where there have been dramatic increases of CO2 around 8000 years ago and CH4 levels 3000 years after that.[113] The correlation between the decrease of CO2 in the Pleistocene and the increase of it during the Holocene implies that the causation of this spark of greenhouse gases into the atmosphere was the growth of human agriculture during the Holocene such as the anthropogenic expansion of (human) land use and irrigation.[92][113]
Climate change
Top:Arid ice age climateMiddle:Atlantic Period, warm and wetBottom: Potential vegetation in climate now if not for human effects like agriculture.[114]
One of the main theories for the extinction's cause is historic climate change.
The climate change theory has suggested that a change in climate near
the end of the late Pleistocene stressed the megafauna to the point of
extinction.[90][115]
Some scientists favor abrupt climate change as the catalyst for the
extinction of the mega-fauna at the end of the Pleistocene, but there
are many who believe increased hunting from early modern humans also
played a part, with others even suggesting that the two interacted.[42][116][117] However, the annual mean temperature of the current interglacial period
for the last 10,000 years is no higher than that of previous
interglacial periods, yet some of the same megafauna survived similar
temperature increases.[118][119][120][121][122][123][excessive citations] In the Americas, a controversial explanation for the shift in climate is presented under the Younger Dryas impact hypothesis, which states that the impact of comets cooled global temperatures.[124][125]
A 2020 study published in Science Advances
found that human population size and/or specific human activities, not
climate change, caused rapidly rising global mammal extinction rates
during the past 126,000 years. Around 96% of all mammalian extinctions
over this time period are attributable to human impacts. According to
Tobias Andermann, lead author of the study, "these extinctions did not
happen continuously and at constant pace. Instead, bursts of extinctions
are detected across different continents at times when humans first
reached them. More recently, the magnitude of human driven extinctions
has picked up the pace again, this time on a global scale."[126][72]
Megafaunal extinction
Megafauna
play a significant role in the lateral transport of mineral nutrients
in an ecosystem, tending to translocate them from areas of high to those
of lower abundance. They do so by their movement between the time they
consume the nutrient and the time they release it through elimination
(or, to a much lesser extent, through decomposition after death).[127] In South America's Amazon Basin,
it is estimated that such lateral diffusion was reduced over 98%
following the megafaunal extinctions that occurred roughly 12,500 years
ago.[128][129] Given that phosphorus
availability is thought to limit productivity in much of the region,
the decrease in its transport from the western part of the basin and
from floodplains (both of which derive their supply from the uplift of
the Andes)
to other areas is thought to have significantly impacted the region's
ecology, and the effects may not yet have reached their limits.[129] The extinction of the mammoths allowed grasslands they had maintained through grazing habits to become birch forests.[44] The new forest and the resulting forest fires may have induced climate change.[44] Such disappearances might be the result of the proliferation of modern humans; some recent studies favor this theory.[46][130]
Large populations of megaherbivores have the potential to contribute greatly to the atmospheric concentration of methane, which is an important greenhouse gas. Modern ruminantherbivores produce methane as a byproduct of foregut fermentation in digestion, and release it through belching or flatulence. Today, around 20% of annual methane emissions come from livestock methane release. In the Mesozoic, it has been estimated that sauropods could have emitted 520 million tons of methane to the atmosphere annually,[131] contributing to the warmer climate of the time (up to 10 °C warmer than at present).[131][132]
This large emission follows from the enormous estimated biomass of
sauropods, and because methane production of individual herbivores is
believed to be almost proportional to their mass.[131]
Recent studies have indicated that the extinction of megafaunal herbivores may have caused a reduction in atmospheric methane. This hypothesis is relatively new.[133] One study examined the methane emissions from the bison that occupied the Great Plains
of North America before contact with European settlers. The study
estimated that the removal of the bison caused a decrease of as much as
2.2 million tons per year.[134] Another study examined the change in the methane concentration in the atmosphere at the end of the Pleistocene epoch after the extinction of megafauna in the Americas. After early humans migrated to the Americas about 13,000 BP,
their hunting and other associated ecological impacts led to the
extinction of many megafaunal species there. Calculations suggest that
this extinction decreased methane production by about 9.6 million tons
per year. This suggests that the absence of megafaunal methane emissions
may have contributed to the abrupt climatic cooling at the onset of the
Younger Dryas.[133] The decrease in atmospheric methane that occurred at that time, as recorded in ice cores,
was 2–4 times more rapid than any other decrease in the last half
million years, suggesting that an unusual mechanism was at work.[133]
Disease
The
hyperdisease hypothesis, proposed by Ross MacPhee in 1997, states that
the megafaunal die-off was due to an indirect transmission of diseases
by newly arriving humans.[135][136] According to MacPhee, aboriginals or animals travelling with them, such as domestic dogs or livestock, introduced one or more highly virulent diseases into new environments whose native population had no immunity to them, eventually leading to their extinction. K-selection animals, such as the now-extinct megafauna, are especially vulnerable to diseases, as opposed to r-selection animals who have a shorter gestation period
and a higher population size. Humans are thought to be the sole cause
as other earlier migrations of animals into North America from Eurasia
did not cause extinctions.[135]
There are many problems with this theory, as this disease would
have to meet several criteria: it has to be able to sustain itself in an
environment with no hosts; it has to have a high infection rate; and be extremely lethal, with a mortality rate of 50–75%. Disease has to be very virulent to kill off all the individuals in a species, and even such a virulent disease as West Nile fever is unlikely to have caused extinction.[137]
There are roughly 880 mountain gorillas remaining. 60% of primate species face an anthropogenically driven extinction crisis and 75% have declining populations.[139]
The loss of animal species from ecological communities, defaunation, is primarily driven by human activity.[41] This has resulted in empty forests, ecological communities depleted of large vertebrates.[46][141] This is not to be confused with extinction, as it includes both the disappearance of species and declines in abundance.[142]
Defaunation effects were first implied at the Symposium of Plant-Animal
Interactions at the University of Campinas, Brazil in 1988 in the
context of Neotropical forests.[143] Since then, the term has gained broader usage in conservation biology as a global phenomenon.[41][143]
Some scholars assert that the emergence of capitalism as the dominant economic system has accelerated ecological exploitation and destruction,[144][145] and has also exacerbated mass species extinction.[146]CUNY professor David Harvey, for example, posits that the neoliberal era "happens to be the era of the fastest mass extinction of species in the Earth's recent history".[147]
Major lobbying organizations representing corporations in the
agriculture, fisheries, forestry and paper, mining, and oil and gas
industries, including the United States Chamber of Commerce,
have been pushing back against legislation that could address the
extinction crisis. A 2022 report by the climate think tank InfluenceMap
stated that "although industry associations, especially in the US,
appear reluctant to discuss the biodiversity crisis, they are clearly
engaged on a wide range of policies with significant impacts on
biodiversity loss."[148]
Big cat
populations have severely declined over the last half-century and could
face extinction in the following decades. According to 2011 IUCN estimates: lions are down to 25,000, from 450,000; leopards are down to 50,000, from 750,000; cheetahs are down to 12,000, from 45,000; tigers are down to 3,000 in the wild, from 50,000.[149] A December 2016 study by the Zoological Society of London, Panthera Corporation and Wildlife Conservation Society
showed that cheetahs are far closer to extinction than previously
thought, with only 7,100 remaining in the wild, existing within only 9%
of their historic range.[150]
Human pressures are to blame for the cheetah population crash,
including prey loss due to overhunting by people, retaliatory killing
from farmers, habitat loss and the illegal wildlife trade.[151]
We are seeing the effects of 7 billion people on the planet. At present rates, we will lose the big cats in 10 to 15 years.
The term pollinator decline
refers to the reduction in abundance of insect and other animal
pollinators in many ecosystems worldwide beginning at the end of the
twentieth century, and continuing into the present day.[152] Pollinators, which are necessary for 75% of food crops, are declining globally in both abundance and diversity.[153] A 2017 study led by Radboud University's
Hans de Kroon indicated that the biomass of insect life in Germany had
declined by three-quarters in the previous 25 years. Participating
researcher Dave Goulson of Sussex University
stated that their study suggested that humans are making large parts of
the planet uninhabitable for wildlife. Goulson characterized the
situation as an approaching "ecological Armageddon", adding that "if we
lose the insects then everything is going to collapse."[154] A 2019 study found that over 40% of insect species are threatened with extinction.[155] The most significant drivers in the decline of insect populations are associated with intensive farming practices, along with pesticide use and climate change.[156] The world's insect population decreases by around 1 to 2 per cent per year.[157]
We have driven the rate of
biological extinction, the permanent loss of species, up several hundred
times beyond its historical levels, and are threatened with the loss of
a majority of all species by the end of the 21st century.
For the first time since the demise
of the dinosaurs 65 million years ago, we face a global mass extinction
of wildlife. We ignore the decline of other species at our peril – for
they are the barometer that reveals our impact on the world that
sustains us.
— Mike Barrett, director of science and policy at WWF's UK branch[178]
Share of species threatened with extinction as of 2019.
Recent extinctions are more directly attributable to human
influences, whereas prehistoric extinctions can be attributed to other
factors, such as global climate change.[41][13] The International Union for Conservation of Nature (IUCN) characterises 'recent' extinction as those that have occurred past the cut-off point of 1500,[179] and at least 875 plant and animal species have gone extinct since that time and 2009.[180] Some species, such as the Père David's deer[181] and the Hawaiian crow,[182] are extinct in the wild, and survive solely in captive populations. Other populations are only locally extinct (extirpated), still existent elsewhere, but reduced in distribution,[183]: 75–77 as with the extinction of gray whales in the Atlantic,[184] and of the leatherback sea turtle in Malaysia.[185]
Humans are rapidly driving the largest vertebrate animals towards
extinction, and in the process interrupting a 66-million-year-old
feature of ecosystems, the relationship between diet and body mass,
which researchers suggest could have unpredictable consequences.[186][187] A 2019 study published in Nature Communications
found that rapid biodiversity loss is impacting larger mammals and
birds to a much greater extent than smaller ones, with the body mass of
such animals expected to shrink by 25% over the next century. Another
2019 study published in Biology Letters found that extinction rates are perhaps much higher than previously estimated, in particular for bird species.[188]
The 2019 Global Assessment Report on Biodiversity and Ecosystem Services
lists the primary causes of contemporary extinctions in descending
order: (1) changes in land and sea use (primarily agriculture and
overfishing respectively); (2) direct exploitation of organisms such as
hunting; (3) anthropogenic climate change; (4) pollution and (5)
invasive alien species spread by human trade.[31] This report, along with the 2020 Living Planet Report by the WWF, both project that climate change will be the leading cause in the next several decades.[31][77]
A June 2020 study published in PNAS
posits that the contemporary extinction crisis "may be the most serious
environmental threat to the persistence of civilization, because it is
irreversible" and that its acceleration "is certain because of the still
fast growth in human numbers and consumption rates." The study found
that more than 500 vertebrate species are poised to be lost in the next two decades.[74]
Humans both create and destroy crop cultivar and domesticated animal varieties. Advances in transportation and industrial farming has led to monoculture
and the extinction of many cultivars. The use of certain plants and
animals for food has also resulted in their extinction, including silphium and the passenger pigeon.[189]
It was estimated in 2012 that 13 percent of Earth's ice-free land
surface is used as row-crop agricultural sites, 26 percent used as
pastures, and 4 percent urban-industrial areas.[190]
In March 2019, Nature Climate Change published a study by ecologists from Yale University,
who found that over the next half century, human land use will reduce
the habitats of 1,700 species by up to 50%, pushing them closer to
extinction.[191][192] That same month PLOS Biology published a similar study drawing on work at the University of Queensland,
which found that "more than 1,200 species globally face threats to
their survival in more than 90% of their habitat and will almost
certainly face extinction without conservation intervention".[193][194]
Since 1970, the populations of migratory freshwater fish have declined by 76%, according to research published by the Zoological Society of London
in July 2020. Overall, around one in three freshwater fish species are
threatened with extinction due to human-driven habitat degradation and
overfishing.[195]
Satellite image of rainforest converted to oil palm plantations.[196]
Some scientists and academics assert that industrial agriculture and the growing demand for meat is contributing to significant global biodiversity loss as this is a significant driver of deforestation and habitat destruction; species-rich habitats, such as the Amazon region and Indonesia[197][198] being converted to agriculture.[43][199][35][200][201] A 2017 study by the World Wildlife Fund
(WWF) found that 60% of biodiversity loss can be attributed to the vast
scale of feed crop cultivation required to rear tens of billions of
farm animals.[36] Moreover, a 2006 report by the Food and Agriculture Organization (FAO) of the United Nations, Livestock's Long Shadow, also found that the livestock sector is a "leading player" in biodiversity loss.[202] More recently, in 2019, the IPBESGlobal Assessment Report on Biodiversity and Ecosystem Services
attributed much of this ecological destruction to agriculture and
fishing, with the meat and dairy industries having a very significant
impact.[33] Since the 1970s food production has soared in order to feed a growing human population and bolster economic growth,
but at a huge price to the environment and other species. The report
says some 25% of the earth's ice-free land is used for cattle grazing.[65] A 2020 study published in Nature Communications
warned that human impacts from housing, industrial agriculture and in
particular meat consumption are wiping out a combined 50 billion years
of earth's evolutionary history (defined as phylogenetic diversity[a]) and driving to extinction some of the "most unique animals on the planet," among them the Aye-aye lemur, the Chinese crocodile lizard and the pangolin.[203][204] Said lead author Rikki Gumbs:
We know from all the data we have
for threatened species, that the biggest threats are agriculture
expansion and the global demand for meat. Pasture land, and the clearing
of rainforests for production of soy, for me, are the largest drivers –
and the direct consumption of animals.[203]
Climate change is expected to be a major driver of extinctions from the 21st century.[31]
Rising levels of carbon dioxide are resulting in influx of this gas
into the ocean, increasing its acidity. Marine organisms which possess calcium carbonate shells or exoskeletons experience physiological pressure as the carbonate reacts with acid. For example, this is already resulting in coral bleaching on various coral reefs worldwide, which provide valuable habitat and maintain a high biodiversity. Marine gastropods, bivalves and other invertebrates are also affected, as are the organisms that feed on them.[206][better source needed]
Some studies have suggested that it is not climate change that is
driving the current extinction crisis, but the demands of contemporary
human civilization on nature.[207][208]
The vaquita,
the world's most endangered marine mammal, was reduced to 30
individuals as of February 2017. They are often killed by commercial
fishing nets.[209] As of March 2019, only 10 remain, according to The International Committee for the Recovery of the Vaquita.[210]
Overhunting can reduce the local population of game animals by more than half, as well as reducing population density, and may lead to extinction for some species.[211] Populations located nearer to villages are significantly more at risk of depletion.[212][213] Several conservationist organizations, among them IFAW and HSUS, assert that trophy hunters,
particularly from the United States, are playing a significant role in
the decline of giraffes, which they refer to as a "silent extinction".[214]
The surge in the mass killings by poachers involved in the illegal ivory trade along with habitat loss is threatening African elephant populations.[215][216] In 1979, their populations stood at 1.7 million; at present there are fewer than 400,000 remaining.[217] Prior to European colonization, scientists believe Africa was home to roughly 20 million elephants.[218] According to the Great Elephant Census, 30% of African elephants (or 144,000 individuals) disappeared over a seven-year period, 2007 to 2014.[216][219] African elephants could become extinct by 2035 if poaching rates continue.[166]
Fishing has had a devastating effect on marine organism
populations for several centuries even before the explosion of
destructive and highly effective fishing practices like trawling.[220] Humans are unique among predators in that they regularly prey on other adult apex predators, particularly in marine environments;[26]bluefin tuna, blue whales, North Atlantic right whales[221] and over fifty species of sharks and rays are vulnerable to predation pressure from human fishing, in particular commercial fishing.[222] A 2016 study published in Science concludes that humans tend to hunt larger species, and this could disrupt ocean ecosystems for millions of years.[223] A 2020 study published in Science Advances found that around 18% of marine megafauna, including iconic species such as the Great white shark,
are at risk of extinction from human pressures over the next century.
In a worst-case scenario, 40% could go extinct over the same time
period.[224] According to a 2021 study published in Nature, 71% of oceanic shark and ray populations have been destroyed by overfishing (the primary driver of ocean defaunation)
from 1970 to 2018, and are nearing the "point of no return" as 24 of
the 31 species are now threatened with extinction, with several being
classified as critically endangered.[225][226][227]
If this pattern goes unchecked, the
future oceans would lack many of the largest species in today’s oceans.
Many large species play critical roles in ecosystems and so their
extinctions could lead to ecological cascades that would influence the
structure and function of future ecosystems beyond the simple fact of
losing those species.
— Jonathan Payne, associate professor and chair of geological sciences at Stanford University[228]
The golden toad of Costa Rica, extinct since around 1989. Its disappearance has been attributed to a confluence of several factors, including El Niño warming, fungus, habitat loss and the introduction of invasive species.[229]
The decline of amphibian populations has also been identified as an
indicator of environmental degradation. As well as habitat loss,
introduced predators and pollution, Chytridiomycosis, a fungal infection accidentally spread by human travel,[42]
globalization and the wildlife trade, has caused severe population
drops of over 500 amphibian species, and perhaps 90 extinctions,[232] including (among many others) the extinction of the golden toad in Costa Rica, the Gastric-brooding frog in Australia, the Rabb's fringe-limbed treefrog and the extinction of the Panamanian golden frog
in the wild. Chytrid fungus has spread across Australia, New Zealand,
Central America and Africa, including countries with high amphibian
diversity such as cloud forests in Honduras and Madagascar. Batrachochytrium salamandrivorans is a similar infection currently threatening salamanders. Amphibians are now the most endangered vertebrate group, having existed for more than 300 million years through three other mass extinctions.[42]: 17
Millions of bats in the US have been dying off since 2012 due to a fungal infection known as white-nose syndrome
that spread from European bats, who appear to be immune. Population
drops have been as great as 90% within five years, and extinction of at
least one bat species is predicted. There is currently no form of
treatment, and such declines have been described as "unprecedented" in
bat evolutionary history by Alan Hicks of the New York State Department of Environmental Conservation.[233]
Megafauna were once found on every continent of the world, but are now almost exclusively found on the continent of Africa. In some regions, megafauna experienced population crashes and trophic cascades shortly after the earliest human settlers.[47][48]
Worldwide, 178 species of the world's largest mammals died out between
52,000 and 9,000 BC; it has been suggested that a higher proportion of
African megafauna survived because they evolved alongside humans.[237][42] The timing of South American megafaunal extinction
appears to precede human arrival, although the possibility that human
activity at the time impacted the global climate enough to cause such an
extinction has been suggested.[42]
Africa
experienced the smallest decline in megafauna compared to the other
continents. This is presumably due to the idea that Afroeurasian
megafauna evolved alongside humans, and thus developed a healthy fear of
them, unlike the comparatively tame animals of other continents.[237][238]
Unlike other continents, the megafauna of Eurasia went extinct over a
relatively long period of time, possibly due to climate fluctuations
fragmenting and decreasing populations, leaving them vulnerable to
over-exploitation, as with the steppe bison (Bison priscus).[239]
The warming of the arctic region caused the rapid decline of
grasslands, which had a negative effect on the grazing megafauna of
Eurasia. Most of what once was mammoth steppe was converted to mire, rendering the environment incapable of supporting them, notably the woolly mammoth.[240]
The passenger pigeon was a species of pigeon endemic to North America.
It experienced a rapid decline in the late 1800s due to habitat
destruction and intense hunting after the arrival of Europeans. The last
wild bird is thought to have been shot in 1901.
There has been a debate as to the extent to which the disappearance of megafauna at the end of the last glacial period can be attributed to human activities by hunting, or even by slaughter[b] of prey populations. Discoveries at Monte Verde in South America and at Meadowcroft Rock Shelter in Pennsylvania have caused a controversy[241] regarding the Clovis culture. There likely would have been human settlements prior to the Clovis culture, and the history of humans in the Americas may extend back many thousands of years before the Clovis culture.[241] The amount of correlation between human arrival and megafauna extinction is still being debated: for example, in Wrangel Island in Siberia the extinction of dwarf woolly mammoths (approximately 2000 BCE)[242]
did not coincide with the arrival of humans, nor did megafaunal mass
extinction on the South American continent, although it has been
suggested climate changes induced by anthropogenic effects elsewhere in
the world may have contributed.[42]
Comparisons are sometimes made between recent extinctions (approximately since the industrial revolution) and the Pleistocene extinction near the end of the last glacial period. The latter is exemplified by the extinction of large herbivores such as the woolly mammoth and the carnivores that preyed on them. Humans of this era actively hunted the mammoth and the mastodon,[243]
but it is not known if this hunting was the cause of the subsequent
massive ecological changes, widespread extinctions and climate changes.[44][45]
The ecosystems encountered by the first Americans had not been
exposed to human interaction, and may have been far less resilient to
human made changes than the ecosystems encountered by industrial era
humans. Therefore, the actions of the Clovis people, despite seeming
insignificant by today's standards could indeed have had a profound
effect on the ecosystems and wild life which was entirely unused to
human influence.[attribution needed][neutrality is disputed][42]
The thunder bird
was a 2-metre (7 ft) tall flightless bird. Evidence of egg cooking in
this species is the first evidence of megafaunal hunting by humans in
Australia.[244]
Australia was once home to a large assemblage of megafauna, with many parallels to those found on the African continent today. Australia's fauna is characterised by primarily marsupial mammals, and many reptiles and birds, all existing as giant forms until recently. Humans arrived on the continent very early, about 50,000 years ago.[42]
The extent human arrival contributed is controversial; climatic drying
of Australia 40,000–60,000 years ago was an unlikely cause, as it was
less severe in speed or magnitude than previous regional climate change
which failed to kill off megafauna. Extinctions in Australia continued
from original settlement until today in both plants and animals, whilst many more animals and plants have declined or are endangered.[245]
Due to the older timeframe and the soil chemistry on the continent, very little subfossil preservation evidence exists relative to elsewhere.[246]
However, continent-wide extinction of all genera weighing over 100
kilograms, and six of seven genera weighing between 45 and 100 kilograms
occurred around 46,400 years ago (4,000 years after human arrival)[247] and the fact that megafauna survived until a later date on the island of Tasmania following the establishment of a land bridge[248] suggest direct hunting or anthropogenic ecosystem disruption such as fire-stick farming as likely causes. The first evidence of direct human predation leading to extinction in Australia was published in 2016.[244]
A 2021 study found that the rate of extinction of Australia's
megafauna is rather unusual, with some generalistic species having gone
extinct earlier while highly specialised ones having become extinct
later or even still surviving today. A mosaic cause of extinction with
different anthropogenic and environmental pressures has been proposed.[249]
Caribbean
Recently extinct flightless birds include Madagascar's elephant bird (left), Mauritius's dodo and the great auk of the Atlantic (bottom right).
Human arrival in the Caribbean around 6,000 years ago is correlated with the extinction of many species.[250] These include many different genera of ground and arboreal sloths across all islands. These sloths were generally smaller than those found on the South American continent. Megalocnus were the largest genus at up to 90 kilograms (200 lb), Acratocnus were medium-sized relatives of modern two-toed sloths endemic to Cuba, Imagocnus also of Cuba, Neocnus and many others.[251]
Macaronesia
The arrival of the first human settlers in the Azores
saw the introduction of invasive plants and livestock to the
archipelago, resulting in the extinction of at least two plant species
on Pico Island.[252] Lacustrine ecosystems were ravaged by human colonisation, as evidenced by hydrogen isotopes from C30 fatty acids recording hypoxic bottom waters caused by eutrophication in Lake Funda on Flores Island beginning between 1500 and 1600 AD.[253]
In the Canary Islands,
native thermophilous woodlands were decimated and two tree taxa were
driven extinct following the arrival of its first humans, primarily as a
result of increased fire clearance and soil erosion and the
introduction of invasive pigs, goats, and rats. Invasive species
introductions accelerated during the Age of Discovery when Europeans first settled the Macaronesian
archipelago. The archipelago's laurel forests, though still negatively
impacted, fared better due to being less suitable for human economic
use.[254]
Cabo Verde,
like the Canary Islands, witnessed precipitous deforestation upon the
arrival of European settlers and various invasive species brought by
them in the archipelago,[255] with the archipelago's thermophilous woodlands suffering the greatest destruction.[254]
Introduced species, overgrazing, increased fire incidence, and soil
degradation have been attributed as the chief causes of Cabo Verde's
ecological devastation.[255][256]
Pacific
Archaeological and paleontological digs on 70 different Pacific islands suggested that numerous species became extinct as people moved across the Pacific, starting 30,000 years ago in the Bismarck Archipelago and Solomon Islands.[257]
It is currently estimated that among the bird species of the Pacific,
some 2000 species have gone extinct since the arrival of humans,
representing a 20% drop in the biodiversity of birds worldwide.[258]
The first human settlers of the Hawaiian islands are thought to have arrived between 300 and 800 CE, with European arrival in the 16th century. Hawaii is notable for its endemism of plants, birds, insects, mollusks and fish;
30% of its organisms are endemic. Many of its species are endangered or
have gone extinct, primarily due to accidentally introduced species and
livestock grazing. Over 40% of its bird species have gone extinct, and
it is the location of 75% of extinctions in the United States.[259]
Extinction has increased in Hawaii over the last 200 years and is
relatively well documented, with extinctions among native snails used as
estimates for global extinction rates.[58]
Radiocarbon dating of multiple subfossil specimens shows that now extinct giant lemurs were present in Madagascar until after human arrival.
Within 500 years of the arrival of humans between 2,500 and 2,000 years ago, nearly all of Madagascar's distinct, endemic and geographically isolated megafauna became extinct.[260]
The largest animals, of more than 150 kilograms (330 lb), were extinct
very shortly after the first human arrival, with large and medium-sized
species dying out after prolonged hunting pressure from an expanding
human population moving into more remote regions of the island around
1000 years ago. The eight or more species of elephant birds, giant flightless ratites in the genera Aepyornis, Vorombe, and Mullerornis, are extinct from over-hunting,[261] as well as 17 species of lemur, known as giant, subfossil lemurs.
Some of these lemurs typically weighed over 150 kilograms (330 lb), and
their fossils have provided evidence of human butchery on many species.[262] Smaller fauna experienced initial increases due to decreased competition, and then subsequent declines over the last 500 years.[48]
All fauna weighing over 10 kilograms (22 lb) died out. The primary
reasons for the decline of Madagascar's biota, which at the time was
already stressed by natural aridification,[263] were human hunting,[264][265] herding,[266][265] farming,[264] and forest clearing,[266]
all of which persist and threaten Madagascar's remaining taxa today.
The natural ecosystems of Madagascar as a whole were further impacted by
the much greater incidence of fire as a result of anthropogenic fire
production; evidence from Lake Amparihibe on the island of Nosy Be
indicates a shift in local vegetation from intact rainforest to a
fire-disturbed patchwork of grassland and woodland between 1300 and 1000
BP.[267]
New Zealand is characterised by its geographic isolation and island biogeography,
and had been isolated from mainland Australia for 80 million years. It
was the last large land mass to be colonised by humans. The arrival of Polynesian settlers circa 12th century resulted in the extinction of all of the islands' megafaunal birds within several hundred years.[268] The moa, large flightless ratites, became extinct within 200 years of the arrival of human settlers.[47] The Polynesians also introduced the Polynesian rat.
This may have put some pressure on other birds but at the time of early
European contact (18th century) and colonisation (19th century) the
bird life was prolific. With them, the Europeans brought various invasive species including ship rats, possums, cats and mustelids which devastated native bird life, some of which had adapted flightlessness and ground nesting habits, and had no defensive behavior as a result of having no native mammalian predators. The kakapo,
the world's biggest parrot, which is flightless, now only exists in
managed breeding sanctuaries. New Zealand's national emblem, the kiwi, is on the endangered bird list.[268]
A 2018 article in Science advocated for the global community to designate 30 percent of the planet by 2030, and 50 percent by 2050, as protected areas
in order to mitigate the contemporary extinction crisis. It highlighted
that the human population is projected to grow to 10 billion by the
middle of the century, and consumption of food and water resources is
projected to double by this time.[276]
In November 2018, the UN's biodiversity chief Cristiana Pașca Palmer
urged people around the world to put pressure on governments to
implement significant protections for wildlife by 2020. She called
biodiversity loss a "silent killer" as dangerous as global warming,
but said it had received little attention by comparison. "It’s
different from climate change, where people feel the impact in everyday
life. With biodiversity, it is not so clear but by the time you feel
what is happening, it may be too late."[277] In January 2020, the UN Convention on Biological Diversity drafted a Paris-style plan to stop biodiversity and ecosystem collapse by setting the deadline of 2030 to protect 30% of the earth's land and oceans and to reduce pollution by 50%, with the goal of allowing for the restoration of ecosystems by 2050. The world failed to meet the Aichi Biodiversity targets for 2020 set by the convention during a summit in Japan in 2010.[278][279] Of the 20 biodiversity targets proposed, only six were "partially achieved" by the deadline.[280] It was called a global failure by Inger Andersen, head of the United Nations Environment Programme:
"From COVID-19 to massive wildfires, floods, melting glaciers and unprecedented heat, our failure to meet the Aichi (biodiversity) targets — protect our our home — has very real consequences. We can no longer afford to cast nature to the side."[281]
Some scientists have proposed keeping extinctions below 20 per year
for the next century as a global target to reduce species loss, which is
the biodiversity equivalent of the 2 °C climate target, although it is
still much higher than the normal background rate of two per year prior
to anthropogenic impacts on the natural world.[282][283]
An October 2020 report on the "era of pandemics" from IPBES found that many of the same human activities that contribute to biodiversity loss and climate change, including deforestation and the wildlife trade, have also increased the risk of future pandemics. The report offers several policy options to reduce such risk, such as taxing meat
production and consumption, cracking down on the illegal wildlife
trade, removing high disease-risk species from the legal wildlife trade,
and eliminating subsidies to businesses which are harmful to the
environment.[284][285][286] According to marine zoologist John Spicer, "the COVID-19 crisis
is not just another crisis alongside the biodiversity crisis and the
climate change crisis. Make no mistake, this is one big crisis – the
greatest that humans have ever faced."[284]
According to a 2021 paper published in Frontiers in Conservation Science,
humanity almost certainly faces a "ghastly future" of mass extinction,
biodiversity collapse, climate change and their impacts unless major
efforts to change human industry and activity are rapidly undertaken.[79][287]
A 2022 report published in Science warned that 44% of
earth's terrestrial surface, or 24.7 million square miles, must to be
conserved and made "ecologically sound" in order to prevent further
biodiversity loss.[288][289]
Phylogenetic
diversity (PD) is the sum of the phylogenetic branch lengths in years
connecting a set of species to each other across their phylogenetic
tree, and measures their collective contribution to the tree of life.
This
may refer to groups of animals endangered by climate change. For
example, during a catastrophic drought, remaining animals would be
gathered around the few remaining watering holes, and thus become
extremely vulnerable.
Hollingsworth, Julia (June 11, 2019). "Almost 600 plant species have become extinct in the last 250 years". CNN. Retrieved January 14, 2020. The
research -- published Monday in Nature, Ecology & Evolution journal
-- found that 571 plant species have disappeared from the wild
worldwide, and that plant extinction is occurring up to 500 times faster
than the rate it would without human intervention.
Rosenberg
KV, Dokter AM, Blancher PJ, Sauer JR, Smith AC, Smith PA, Stanton JC,
Panjabi A, Helft L, Parr M, Marra PP (2019). "Decline of the North
American avifauna". Science. 366 (6461): 120–124. doi:10.1126/science.aaw1313. PMID31604313. S2CID203719982.
Barnosky, Anthony D.;
Matzke, Nicholas; Tomiya, Susumu; Wogan, Guinevere O. U.; Swartz,
Brian; Quental, Tiago B.; Marshall, Charles; McGuire, Jenny L.; Lindsey,
Emily L.; Maguire, Kaitlin C.; Mersey, Ben; Ferrer, Elizabeth A. (3
March 2011). "Has the Earth's sixth mass extinction already arrived?". Nature. 471 (7336): 51–57. Bibcode:2011Natur.471...51B. doi:10.1038/nature09678. PMID21368823. S2CID4424650.
"Without humans, the whole world could look like Serengeti". EurekAlert!. Retrieved August 16, 2020. The
existence of Africa's many species of mammals is thus not due to an
optimal climate and environment, but rather because it is the only place
where they have not yet been eradicated by humans. The underlying
reason includes evolutionary adaptation of large mammals to humans as
well as greater pest pressure on human populations in long-inhabited
Africa in the past.
McNeill, John Robert; Engelke, Peter (2016). The Great Acceleration: An Environmental History of the Anthropocene since 1945 (1st ed.). Harvard University Press. ISBN978-0674545038.
Daly, Herman E.; Farley, Joshua C. (2010). Ecological economics, second edition: Principles and applications. Island Press. ISBN9781597266819.
Fricke,
Evan C.; Hsieh, Chia; Middleton, Owen; Gorczynski, Daniel; Cappello,
Caroline D.; Sanisidro, Oscar; Rowan, John; Svenning, Jens-Christian;
Beaudrot, Lydia (August 25, 2022). "Collapse of terrestrial mammal food
webs since the Late Pleistocene". Science. 377 (6609): 1008–1011. doi:10.1126/science.abn4012. PMID36007038. S2CID251843290. Food
webs underwent steep regional declines in complexity through loss of
food web links after the arrival and expansion of human populations. We
estimate that defaunation has caused a 53% decline in food web links globally.
Stokstad, Erik (5 May 2019). "Landmark analysis documents the alarming global decline of nature". Science. AAAS. Retrieved 26 August 2020. For
the first time at a global scale, the report has ranked the causes of
damage. Topping the list, changes in land use—principally
agriculture—that have destroyed habitat. Second, hunting and other kinds
of exploitation. These are followed by climate change, pollution, and
invasive species, which are being spread by trade and other activities.
Climate change will likely overtake the other threats in the next
decades, the authors note. Driving these threats are the growing human
population, which has doubled since 1970 to 7.6 billion, and
consumption. (Per capita of use of materials is up 15% over the past 5
decades.)
Ripple WJ, Wolf C, Newsome TM, Galetti M, Alamgir M, Crist E, Mahmoud MI, Laurance WF (13 November 2017). "World Scientists' Warning to Humanity: A Second Notice"(PDF). BioScience. 67 (12): 1026–1028. doi:10.1093/biosci/bix125. Archived from the original(PDF) on 15 December 2019. Retrieved 12 July 2018. Moreover,
we have unleashed a mass extinction event, the sixth in roughly 540
million years, wherein many current life forms could be annihilated or
at least committed to extinction by the end of this century.
McGrath, Matt (6 May 2019). "Humans 'threaten 1m species with extinction'". BBC. Retrieved 3 August 2021. Pushing
all this forward, though, are increased demands for food from a growing
global population and specifically our growing appetite for meat and
fish.
Grayson,
Donald K.; Meltzer, David J. (December 2012). "Clovis Hunting and Large
Mammal Extinction: A Critical Review of the Evidence". Journal of World Prehistory. 16 (4): 313–359. doi:10.1023/A:1022912030020. S2CID162794300.
Perry,
George L. W.; Wheeler, Andrew B.; Wood, Jamie R.; Wilmshurst, Janet M.
(2014-12-01). "A high-precision chronology for the rapid extinction of
New Zealand moa (Aves, Dinornithiformes)". Quaternary Science Reviews. 105: 126–135. Bibcode:2014QSRv..105..126P. doi:10.1016/j.quascirev.2014.09.025.
Crowley, Brooke E. (2010-09-01). "A refined chronology of prehistoric Madagascar and the demise of the megafauna". Quaternary Science Reviews. Special Theme: Case Studies of Neodymium Isotopes in Paleoceanography. 29 (19–20): 2591–2603. Bibcode:2010QSRv...29.2591C. doi:10.1016/j.quascirev.2010.06.030.
Woodward, Aylin (April 8, 2019). "So many animals are going extinct that it could take Earth 10 million years to recover". Business Insider. Retrieved April 9, 2019. Lowery
doesn't think we've strayed into Sixth Extinction territory yet. But he
and Fraass agree that squabbling over what constitutes that distinction
is beside the point. "We have to work to save biodiversity before it's
gone. That's the important takeaway here," Lowery said. There is
consensus on one aspect of the extinction trend, however: Homo sapiens
are to blame. According to a 2014 study, current extinction rates are
1,000 times higher than they would be if humans weren't around.
Brannen, Peter (13 June 2017). "Earth Is Not in the Midst of a Sixth Mass Extinction". The Atlantic. Retrieved 28 November 2020. Many
of those making facile comparisons between the current situation and
past mass extinctions don’t have a clue about the difference in the
nature of the data, much less how truly awful the mass extinctions
recorded in the marine fossil record actually were.
Dasgupta, Partha (2021). "The Economics of Biodiversity: The Dasgupta Review Headline Messages"(PDF). UK government. p. 1. Retrieved December 15, 2021. Biodiversity
is declining faster than at any time in human history. Current
extinction rates, for example, are around 100 to 1,000 times higher than
the baseline rate, and they are increasing.
Bradshaw,
Corey J. A.; Ehrlich, Paul R.; Beattie, Andrew; Ceballos, Gerardo;
Crist, Eileen; Diamond, Joan; Dirzo, Rodolfo; Ehrlich, Anne H.; Harte,
John; Harte, Mary Ellen; Pyke, Graham; Raven, Peter H.; Ripple, William
J.; Saltré, Frédérik; Turnbull, Christine; Wackernagel, Mathis;
Blumstein, Daniel T. (2021). "Underestimating the Challenges of Avoiding a Ghastly Future". Frontiers in Conservation Science. 1. doi:10.3389/fcosc.2020.615419.
Cowie, Robert H.; Bouchet, Philippe; Fontaine, Benoît (2022). "The Sixth Mass Extinction: fact, fiction or speculation?". Biological Reviews. 97 (2): 640–663. doi:10.1111/brv.12816. PMID35014169. S2CID245889833. Our
review lays out arguments clearly demonstrating that there is a
biodiversity crisis, quite probably the start of the Sixth Mass
Extinction.
National Geographic Society (June 7, 2019). "Anthropocene". National Geographic. Retrieved 23 November 2021. coined and made popular by biologist Eugene Stormer and chemist Paul Crutzen in 2000.
Zalasiewicz,
Jan; Williams, Mark; Smith, Alan; Barry, Tiffany L.; Coe, Angela L.;
Bown, Paul R.; Brenchley, Patrick; Cantrill, David; Gale, Andrew;
Gibbard, Philip; Gregory, F. John; Hounslow, Mark W.; Kerr, Andrew C.;
Pearson, Paul; Knox, Robert; Powell, John; Waters, Colin; Marshall,
John; Oates, Michael; Rawson, Peter; Stone, Philip (2008). "Are we now living in the Anthropocene". GSA Today. 18 (2): 4. doi:10.1130/GSAT01802A.1.
Waters,
Colin N.; Zalasiewicz, Jan; Summerhayes, Colin; Barnosky, Anthony D.;
Poirier, Clément; Gałuszka, Agnieszka; Cearreta, Alejandro; Edgeworth,
Matt; Ellis, Erle C. (2016-01-08). "The Anthropocene is functionally and
stratigraphically distinct from the Holocene". Science. 351 (6269). aad2622. doi:10.1126/science.aad2622. ISSN0036-8075. PMID26744408. S2CID206642594.
Teyssèdre, A.; Couvet, D. (2007). "Expected impact of agriculture expansion on the global avifauna". C. R. Biologies. 30 (3): 247–254. doi:10.1016/j.crvi.2007.01.003. PMID17434119.
Graham,
R. W.; Mead, J. I. (1987). "Environmental fluctuations and evolution of
mammalian faunas during the last deglaciation in North America". In
Ruddiman, W. F.; Wright, J. H. E. (eds.). North America and Adjacent Oceans During the Last Deglaciation. The Geology of North America. Vol. K-3. Geological Society of America. ISBN978-0-8137-5203-7.
Martin, P. S. (1967). "Prehistoric overkill". In Martin, P. S.; Wright, H. E. (eds.). Pleistocene extinctions: The search for a cause. New Haven: Yale University Press. ISBN978-0-300-00755-8.
Andersen,
S. T. (1973). "The differential pollen productivity of trees and its
significance for the interpretation of a pollen diagram from a forested
region". In Birks, H.J.B.; West, R.G. (eds.). Quaternary plant ecology: the 14th symposium of the British Ecological society, University of Cambridge, 28–30 March 1972. Oxford: Blackwell Scientific. ISBN978-0-632-09120-1.
Birks, H.H. (1973). "Modern macrofossil assemblages in lake sediments in Minnesota". In Birks, H. J. B.; West, R. G. (eds.). Quaternary plant ecology: the 14th symposium of the British Ecological Society, University of Cambridge, 28–30 March 1972. Oxford: Blackwell Scientific. ISBN978-0-632-09120-1.
Davis, M. B. (1976). "Pleistocene biogeography of temperate deciduous forests". Geoscience and man: Ecology of the Pleistocene. Vol. 13. Baton Rouge: School of Geoscience, Louisiana State University.
MacPhee,
Ross D.E.; Marx, Preston A. (1997). "The 40,000-year Plague: Humans,
Hyperdisease, and First-Contact Extinctions". In Goodman, S.;
Patterson, B.D. (eds.). Natural Change and Human Impact in Madagascar. Washington D.C.: Smithsonian Institution Press. pp. 169–217. ISBN978-1-56098-683-6.
Hickel, Jason (2021). Less is More: How Degrowth Will Save the World. Windmill Books. pp. 39–40. ISBN978-1786091215. It
was only with the rise of capitalism over the past few hundred years,
and the breathtaking acceleration of industrialization from the 1950s,
that on a planetary scale things began to tip out of balance.
Duranta,
Sarah M.; Mitchell, Nicholas; Groom, Rosemary; Pettorelli, Nathalie;
Ipavec, Audrey; Jacobson, Andrew P.; Woodroffe, Rosie; Böhm, Monika;
Hunter, Luke T. B.; Becker, Matthew S.; Broekhuis, Femke; Bashir,
Sultana; Andresen, Leah; Aschenborn, Ortwin; Beddiaf, Mohammed;
Belbachir, Farid; Belbachir-Bazi, Amel; Berbash, Ali; Brandao de Matos
Machado, Iracelma; Breitenmoser, Christine; et al. (2016). "The global decline of cheetah Acinonyx jubatus and what it means for conservation". Proceedings of the National Academy of Sciences of the United States of America. 114 (3): 1–6. doi:10.1073/pnas.1611122114. PMC5255576. PMID28028225.
Sánchez-Bayo, Francisco; Wyckhuys, Kris A.G. (April 2019). "Worldwide decline of the entomofauna: A review of its drivers". Biological Conservation. 232: 8–27. doi:10.1016/j.biocon.2019.01.020. S2CID91685233.
Ripple,
William J.; Wolf, Christopher; Newsome, Thomas M.; Betts, Matthew G.;
Ceballos, Gerardo; Courchamp, Franck; Hayward, Matt W.; Van Valkenburgh,
Blaire; Wallach, Arian D.; Worm, Boris (2019). "Are we eating the world's megafauna to extinction?". Conservation Letters. 12 (3). e12627. doi:10.1111/conl.12627.
"History of the Convention". Secretariat of the Convention on Biological Diversity. Retrieved 9 January 2017.
Glowka, Lyle; Burhenne-Guilmin, Françoise; Synge, Hugh; McNeely, Jeffrey A.; Gündling, Lothar (1994). IUCN environmental policy and law paper. Guide to the Convention on Biodiversity. International Union for Conservation of Nature. ISBN978-2-8317-0222-3.
Briggs, Helen (May 26, 2020). "'Billions of years of evolutionary history' under threat". BBC. Retrieved October 5, 2020. The
researchers calculated the amount of evolutionary history - branches on
the tree of life - that are currently threatened with extinction, using
extinction risk data for more than 25,000 species. They found a
combined 50 billion years of evolutionary heritage, at least, were under
threat from human impacts such as urban development, deforestation and
road building.
Ketcham, Christopher (December 3, 2022). "Addressing Climate Change Will Not "Save the Planet"". The Intercept. Retrieved December 6, 2022. When
it comes to effects on wildlife, climate change is more like a mule,
slow and plodding. Yes, a warmed atmosphere is projected to be a
significant factor in the extinction crisis in future decades, but
what’s destroying species today is habitat fragmentation and loss,
overhunting and overexploitation, agricultural expansion, pollution, and
industrial development. It isn’t climate change that caused a 69
percent loss in total wildlife populations between 1970 and 2018,
according to a World Wildlife Fund study published this year. The cause
is too many people demanding too much from ecosystems, or human
overshoot of the biophysical carrying capacity of the Earth.
Caro,
Tim; Rowe, Zeke; et al. (2022). "An inconvenient misconception:
Climate change is not the principal driver of biodiversity loss". Conservation Letters (15): e12868. doi:10.1111/conl.12868.
Peres,
Carlos A.; Nascimento, Hilton S. (2006). "Impact of Game Hunting by the
Kayapo´ of South-eastern Amazonia: Implications for Wildlife
Conservation in Tropical Forest Indigenous Reserves". Human Exploitation and Biodiversity Conservation. Topics in Biodiversity and Conservation. Vol. 3. pp. 287–313. ISBN978-1-4020-5283-5.
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M.; Boaglio, G. (2004). "Distribution and Relative Abundance of
Peccaries in the Argentine Chaco: Associations with Human Factors". Biological Conservation. 116 (2): 217–225. doi:10.1016/S0006-3207(03)00192-7.
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D. S.; Hicks, A. C.; Behr, M.; Meteyer, C. U.; Berlowski-Zier, B. M.;
Buckles, E. L.; Coleman, J. T. H.; Darling, S. R.; Gargas, A.; Niver,
R.; Okoniewski, J. C.; Rudd, R. J.; Stone, W. B. (9 January 2009). "Bat
White-Nose Syndrome: An Emerging Fungal Pathogen?". Science. 323 (5911): 227. doi:10.1126/science.1163874. PMID18974316. S2CID23869393.
Pushkina, D.; Raia, P. (2008). "Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna". Journal of Human Evolution. 54 (6): 769–782. doi:10.1016/j.jhevol.2007.09.024. PMID18199470.
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V. V.; Nikolsky, P. A.; Girya, E. Y.; Basilyan, A. E.; Tumskoy, V. E.;
Koulakov, S. A.; Astakhov, S. N.; Pavlova, E. Y.; Anisimov, M. A.
(2004). "The Yana RHS site: Humans in the Arctic before the Last Glacial
Maximum". Science. 303 (5654): 52–56. Bibcode:2004Sci...303...52P. doi:10.1126/science.1085219. PMID14704419. S2CID206507352.
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David A; Burney, Lida Pigott; Godfrey, Laurie R; Jungers, William L;
Goodman, Steven M; Wright, Henry T; Jull, A J Timothy (2004-07-01). "A
chronology for late prehistoric Madagascar". Journal of Human Evolution. 47 (1–2): 25–63. doi:10.1016/j.jhevol.2004.05.005. PMID15288523.
Hawkins, A. F. A.; Goodman, S. M. (2003). Goodman, S. M.; Benstead, J. P. (eds.). The Natural History of Madagascar. University of Chicago Press. pp. 1026–1029. ISBN978-0-226-30307-9.
Perez,
Ventura R.; Godfrey, Laurie R.; Nowak-Kemp, Malgosia; Burney, David A.;
Ratsimbazafy, Jonah; Vasey, Natalia (2005-12-01). "Evidence of early
butchery of giant lemurs in Madagascar". Journal of Human Evolution. 49 (6): 722–742. doi:10.1016/j.jhevol.2005.08.004. PMID16225904.
Büscher
B, Fletcher R, Brockington D, Sandbrook C, Adams W, Campbell L, Corson
C, Dressler W, Duffy R, Gray N, Holmes G, Kelly A, Lunstrum E,
Ramutsindela M, Shanker K (2017). "Half-Earth or Whole Earth? Radical
ideas for conservation, and their implications". Oryx. 51 (3): 407–410. doi:10.1017/S0030605316001228. S2CID56573294.
Kopina
H, Washington H, Gray J, Taylor B (2018). "The "future of conservation"
debate: defending ecocentrism and the Nature Needs Half movement". Biological Conservation. 217: 140–148. doi:10.1016/j.biocon.2017.10.016. ISSN0006-3207. S2CID89930104.
Noss
R, Dobson A, Baldwin R, Beier P, Davis C, Dellasala D, Francis J, Locke
H, Nowak K, Lopez R, Reining C, Trombulak S, Tabor G (2012). "Bolder
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Allan,
James R.; Possingham, Hugh P.; Atkinson, Scott C.; Waldron, Anthony;
et al. (2 June 2022). "The minimum land area requiring conservation
attention to safeguard biodiversity". Science. 376 (6597): 1094–1101. doi:10.1126/science.abl9127. hdl:11573/1640006. PMID35653463. S2CID233423065.
deBuys, William (March 2015). "The Politics of Extinction – A Global War on Nature". Tom Dispatch. Uncounted species – not just tigers, gibbons, rhinos, and saola,
but vast numbers of smaller mammals, amphibians, birds, and reptiles –
are being pressed to the brink. We’ve hardly met them and yet, within
the vastness of the universe, they and the rest of Earth’s biota are our
only known companions. Without them, our loneliness would stretch to
infinity.
McCallum, Malcolm L. (2015). "Vertebrate biodiversity losses point to sixth mass extinction". Biodiversity and Conservation. 24 (10): 2497–2519. doi:10.1007/s10531-015-0940-6. S2CID16845698.
Newman, Lenore (2019). Lost Feast: Culinary Extinction and the Future of Food. ECW Press. ISBN978-1770414358.
Nihjuis, Michelle (23 July 2012). "Conservationists Use Triage to Determine Which Species to Save and Not". Scientific American.
The eruptions continued for roughly two million years and spanned the Permian–Triassic
boundary, or P–T boundary, which occurred around 251.9 million years
ago. The Siberian Traps are believed to be the primary cause of the Permian–Triassic extinction event, the most severe extinction event in the geologic record.[1][2]
Large volumes of basalticlava covered a large expanse of Siberia in a flood basalt event. Today, the area is covered by about 7 million km2 (3 million sq mi) of basaltic rock, with a volume of around 4 million km3 (1 million cu mi).[3]
https://en.wikipedia.org/wiki/Siberian_Traps
A lithosphere (from Ancient Greekλίθος (líthos) 'rocky', and σφαίρα (sphaíra) 'sphere') is the rigid,[1] outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy.
https://en.wikipedia.org/wiki/Lithosphere
Volcanic pipes or volcanic conduits are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. They are considered to be a type of diatreme. Volcanic pipes are composed of a deep, narrow cone of solidified magma (described as "carrot-shaped"), and are usually largely composed of one of two characteristic rock types — kimberlite or lamproite. These rocks reflect the composition of the volcanoes' deep magma sources, where the Earth is rich in magnesium. Volcanic pipes are relatively rare. They are well known as the primary source of diamonds, and are mined for this purpose.
https://en.wikipedia.org/wiki/Volcanic_pipe
Underground living refers to living below the ground's surface, whether in natural or manmade caves
or structures. Underground dwellings are an alternative to above-ground
dwellings for some home seekers, including those who are looking to
minimize impact on the environment.
Factories and office buildings can benefit from underground facilities
for many of the same reasons as underground dwellings such as noise
abatement, energy use, and security.
The Boeing MQ-28 Ghost Bat, previously known as the Boeing Airpower Teaming System (ATS) and the Loyal Wingman project, is a stealth, multirole, unmanned aerial vehicle in development by Boeing Australia for the Royal Australian Air Force
(RAAF). It is designed as a force multiplier aircraft capable of flying
alongside manned aircraft for support and performing autonomous
missions independently using artificial intelligence.[4]
MQ-28 Ghost Bat
A Boeing MQ-28 Ghost Bat during a high-speed taxi test
The Lockheed Have Blue was born out of a requirement to evade radar detection. During the Vietnam War,
radar-guided SAMs and AAA posed a significant threat to US aircraft.
For this reason, strike aircraft during the war often required support
aircraft to perform combat air patrols and suppression of enemy air defenses (SEAD).[3] The 1973 Yom Kippur War again highlighted the vulnerability of aircraft to SAMs – the Israeli Air Force lost 109 aircraft in 18 days.[3] During the Cold War, the Soviet Union
developed an integrated defense network, central to which were medium-
to long-range surveillance radars. SAMs and AAAs would be set up around
key locations to defend them from incoming enemy aircraft.[3]
If the loss ratio of Israel during the Yom Kippur War was experienced
by NATO forces during a military confrontation with the Warsaw Pact,
NATO aircraft numbers would be depleted within two weeks.[3]
![{\displaystyle {\frac {[\alpha _{K^{+}}][\alpha _{{UO_{2}}^{2+}}][\alpha _{{H_{2}}S{O_{4}}}]}{[\alpha _{H^{+}}]}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/c7b3de400961d8aae0e1dfa5fd005e03543303b4)
![{\displaystyle {\frac {[\alpha _{Na^{+}}][\alpha _{{U{O_{2}}}^{2+}}][\alpha _{{H_{2}}{S{0_{4}}}}]}{[\alpha _{H^{+}}]}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/8cde95162bb9f62431bb63fe62fce54d76c0bf07)
![{\displaystyle {\frac {[\alpha _{Ca^{2+}}][\alpha _{{UO_{2}}^{2+}}][\alpha _{{H_{2}}S{O_{4}}}]}{[\alpha _{H^{+}}]}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/06e5e89441df99ba20969df60ef878e3ed0b6b0e)
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