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Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.
Relationship between extinction rates and the time interval over which the rates were calculated, for mammals. Each small grey datum point represents the E/MSY (extinction per million species-years) calculated from taxon durations recorded in the Paleobiology Database30 (million-year-or-more time bins) or from lists of extant, recently extinct, and Pleistocene species compiled from the literature (100,000-year-and-less time bins)6, 32, 33, 89, 90, 91, 92, 93, 94, 95, 96, 97. More than 4,600 data points are plotted and cluster on top of each other. Yellow shading encompasses the ‘normal’ (non-anthropogenic) range of variance in extinction rate that would be expected given different measurement intervals; for more than 100,000 years, it is the same as the 95% confidence interval, but the fading to the right indicates that the upper boundary of ‘normal’ variance becomes uncertain at short time intervals. The short horizontal lines indicate the empirically determined mean E/MSY for each time bin. Large coloured dots represent the calculated extinction rates since 2010. Red, the end-Pleistocene extinction event. Orange, documented historical extinctions averaged (from right to left) over the last 1, 30, 50, 70, 100, 500, 1,000 and 5,000 years. Blue, attempts to enhance comparability of modern with fossil data by adjusting for extinctions of species with very low fossilization potential (such as those with very small geographic ranges and bats). For these calculations, ‘extinct’ and ‘extinct in the wild’ species that had geographic ranges less than 500 km2 as recorded by the IUCN6, all species restricted to islands of less than 105 km2, and bats were excluded from the counts (under-representation of bats as fossils is indicated by their composing only about 2.5% of the fossil species count, versus around 20% of the modern species count30). Brown triangles represent the projections of rates that would result if ‘threatened’ mammals go extinct within 100, 500 or 1,000 years. The lowest triangle (of each vertical set) indicates the rate if only ‘critically endangered’ species were to go extinct (CR), the middle triangle indicates the rate if ‘critically endangered’ + ‘endangered’ species were to go extinct (EN), and the highest triangle indicates the rate if ‘critically endangered’ + ‘endangered’ + ‘vulnerable’ species were to go extinct (VU). To produce we first determined the last-occurrence records of Cenozoic mammals from the Paleobiology Database30, and the last occurrences of Pleistocene and Holocene mammals from refs 6, 32, 33 and 89–97. We then used R-scripts (written by N.M.) to compute total diversity, number of extinctions, proportional extinction, and E/MSY (and its mean) for time-bins of varying duration. Cenozoic time bins ranged from 25 million to a million years. Pleistocene time bins ranged from 100,000 to 5,000 years, and Holocene time bins from 5,000 years to a year. For Cenozoic data, the mean E/MSY was computed using the average within-bin standing diversity, which was calculated by counting all taxa that cross each 100,000-year boundary within a million-year bin, then averaging those boundary-crossing counts to compute standing diversity for the entire million-year-and-over bin. For modern data, the mean was computed using the total standing diversity in each bin (extinct plus surviving taxa). This method may overestimate the fossil mean extinction rate and underestimate the modern means, so it is a conservative comparison in terms of assessing whether modern means are higher. The Cenozoic data are for North America and the Pleistocene and Holocene data are for global extinction; adequate global Cenozoic data are unavailable. There is no apparent reason to suspect that the North American average would differ from the global average at the million-year timescale.
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REVIEW doi:10.1038/nature09678
Has the Earth’s sixth mass extinction
already arrived?
Anthony D. Barnosky
1,2,3
, Nicholas Matzke
1
, Susumu Tomiya
1,2,3
, Guinevere O. U. Wogan
1,3
, Brian Swartz
1,2
, Tiago B. Quental
1,2
{,
Charles Marshall
1,2
, Jenny L. McGuire
1,2,3
{, Emily L. Lindsey
1,2
, Kaitlin C. Maguire
1,2
, Ben Mersey
1,4
& Elizabeth A. Ferrer
1,2
Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a
geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a
sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here
we review how differences between fossil and modern data and the addition of recently available palaeontological
information influence our understanding of the current extinction crisis. Our results confirm that current extinction
rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.
Of the four billion species estimated to have evolved on the Earth
over the last 3.5 billion years, some 99% are gone
1
. That shows
how very common extinction is, but normally it is balanced by
speciation. The balance wavers such that at several times in life’s history
extinction rates appear somewhat elevated, but only five times qualify
for ‘mass extinction’ status: near the end of the Ordovician, Devonian,
Permian, Triassic and Cretaceous Periods
2,3
. These are the ‘Big Five’
mass extinctions (two are technically ‘mass depletions’)
4
. Different
causes are thought to have precipitated the extinctions (Table 1), and
the extent of each extinction above the background level varies depend-
ing on analytical technique
4,5
, but they all stand out in having extinction
rates spiking higher than in any other geological interval of the last ,540
million years
3
and exhibiting a loss of over 75% of estimated species
2
.
Increasingly, scientists are recognizing modern extinctionsof species
6,7
and populations
8,9
. Documented numbers are likely to be serious under-
estimates, because most species have not yet been formally described
10,11
.
Such observations suggest that humans are now causing the sixth mass
extinction
10,12–17
, through co-opting resources, fragmenting habitats,
introducing non-native species, spreading pathogens, killing species
directly, and changing global climate
10,12–20
. If so, recovery of biodiversity
will not occur on any timeframe meaningful to people: evolution of new
species typically takes at least hundreds of thousands of years
21,22
, and
recovery from mass extinction episodes probably occurs on timescales
encompassing millions of years
5,23
.
Although there are many definitions of mass extinction and grada-
tions of extinction intensity
4,5
, here we take a conservative approach to
assessing the seriousness of the ongoing extinction crisis, by setting a
high bar for recognizing mass extinction, that is, the extreme diversity
loss that characterized the very unusual Big Five (Table 1). We find that
the Earth could reach that extreme within just a few centuries if current
threats to many species are not alleviated.
Data disparities
Only certain kinds of taxa (primarily those with fossilizable hard parts)
and a restricted subset of the Earth’s biomes (generally in temperate
latitudes) have data sufficient for direct fossil-to-modern comparisons
1
Department of Integrative Biology, University of California, Berkeley, California 94720, USA.
2
University of California Museum of Paleontology, California, USA.
3
University of California Museum of
Vertebrate Zoology, California, USA.
4
Human Evolution Research Center, California, USA. {Present addresses: Departamento de Ecologia, Universidade de Sa
˜o Paulo (USP), Sa
˜o Paulo, Brazil (T.B.Q.);
National Evolutionary Synthesis Center, 2024 W. Main Street, Suite A200, Durham, North Carolina 27705, USA (J.L.M.).
Table 1
|
The ‘Big Five’ mass extinction events
Event Proposed causes
The Ordovician event
64–66
ended ,443 Myr ago; within 3.3 to
1.9 Myr 57% of genera were lost, an estimated 86% of species.
Onset of alternating glacial and interglacial episodes; repeated marine transgressions and
regressions. Uplift and weathering of the Appalachians affecting atmospheric and ocean chemistry.
Sequestration of CO
2
.
The Devonian event
4,64,67–70
ended ,359 Myr ago; within 29 to
2 Myr 35% of genera were lost, an estimated 75% of species.
Global cooling (followed by global warming), possibly tied to the diversification of land plants, with
associated weathering, paedogenesis, and the drawdown of global CO
2
. Evidence for widespread
deep-water anoxia and the spread of anoxic waters by transgressions. Timing and importance of
bolide impacts still debated.
The Permian event
54,71–73
ended ,251 Myr ago; within
2.8 Myr to 160Kyr 56% of genera were lost, an estimated
96% of species.
Siberian volcanism. Global warming. Spread of deep marine anoxic waters. Elevated H
2
SandCO
2
concentrations in both marine and terrestrial realms. Ocean acidification. Evidence for a bolide
impact still debated.
The Triassic event
74,75
ended ,200 Myr ago; within 8.3Myr
to 600 Kyr 47% of genera were lost, an estimated 80% of
species.
Activity in the Central Atlantic Magmatic Province (CAMP) thought to have elevated atmospheric
CO
2
levels, which increased global temperatures and led to a calcification crisis in the world oceans.
The Cretaceous event
58–60,76–79
ended ,65 Myr ago; within
2.5 Myr to less than a year 40% of genera were lost, an
estimated 76% of species.
A bolide impact in the Yucata
´n is thought to have led to a global cataclysm and caused rapid cooling.
Preceding the impact, biota may have been declining owing to a variety of causes: Deccan
volcanism contemporaneous with global warming; tectonic uplift altering biogeography and
accelerating erosion, potentially contributing to ocean eutrophication and anoxic episodes. CO
2
spike just before extinction, drop during extinction.
Myr, million years. Kyr, thousand years.
3MARCH2011|VOL471|NATURE| 51
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(Box 1). Fossils are widely acknowledged to be a biased and incomplete
sample of past species, but modern data also have important biases that,
if not accounted for, can influence global extinction estimates. Only a
tiny fraction (,2.7%) of the approximately 1.9 million named, extant
species have been formally evaluated for extinction status by the
International Union for Conservation of Nature (IUCN). These IUCN
compilations are the best available, but evaluated species represent just a
few twigs plucked from the enormous number of branches that compose
the tree of life. Even for clades recorded as 100% evaluated, many species
still fall into the Data Deficient (DD) category
24
. Also relevant is that not
all of the partially evaluated clades have had their species sampled in the
same way: some are randomly subsampled
25
, and others are evaluated as
opportunity arises or because threats seem apparent. Despite the limita-
tions of both the fossil and modern records, by working around the
diverse data biases it is possible to avoid errors in extrapolating from
what we do know to inferring global patterns. Our goal here is to high-
light some promising approaches (Table 2).
Defining mass extinctions relative to the Big Five
Extinction involves both rate and magnitude, which are distinct but
intimately linked metrics
26
. Rate is essentially the number of extinctions
divided by the time over which the extinctions occurred. One can also
derive from this a proportional rate—the fraction of species that have
gone extinct per unit time. Magnitude is the percentage of species that
have gone extinct. Mass extinctions were originally diagnosed by rate:
the pace of extinction appeared to become significantly faster than
background extinction
3
. Recent studies suggest that the Devonian and
Triassic events resulted more from a decrease in origination rates than
an increase in extinction rates
4,5
. Either way, the standing crop of the
Earth’s species fell by an estimated 75% or more
2
. Thus, mass extinction,
in the conservative palaeontological sense, is when extinction rates
accelerate relative to origination rates such that over 75% of species
disappearwithin a geologicallyshort interval—typically less than 2 million
years, in some cases much less (see Table 1). Therefore, to document
where the current extinction episode lies on the mass extinction scale
defined by the Big Five requires us to know both whether current extinc-
tion rates are above background rates (and if so, how far above) and how
closely historic and projected biodiversity losses approach 75% of the
Earth’s species.
Background rate comparisons
Landmark studies
12,14–17
that highlighted a modern extinction crisis
estimated current rates of extinction to be orders of magnitude higher
than the background rate (Table 2). A useful and widely applied metric
BOX 1
Severe data comparison problems
Geography
The fossil record is very patchy, sparsest in upland environments and tropics, but modern global distributions are known for many species.
A possible comparative technique could be to examine regions or biomes where both fossil an d modern data exist—such as the near-shore marine
realm including coral reefs and terrestrial depositional lowlands (river valleys, coastlines, and lake basins). Currently available databases
6
could be
used to identify modern taxa with geographic ranges indicating low fossilization potential and then extract them from the current-extinction equation.
Taxa available for study
The fossil record usually includes only species that possess identifiable anatomical hard parts that fossilize well. Theoretically all living species
could be studied, but in practice extinction analyses often rely on the small subset of species evaluated by the IUCN. Evaluation following IUCN
procedures
34
places species in one of the following categories: extinct (EX), extinct in the wild (EW), critically endangered (CR), endangered (EN),
vulnerable (VU), near threatened (NT), least concern (LC), or data deficient (DD, information insufficient to reliably determine extinction risk).Species
in the EX and EW categories are typically counted as functionally extinct. Those in the CR plus EN plus VU categories are counted as ‘threatened’.
Assignment to CR, EN or VU is based on how high the risk of extinction is determined to be using five criteria
34
(roughly,CR probability of extinction
exceeds 0.50 in ten years or threegenerations; ENprobability of extinction exceeds 0.20 in 20 years or five generations; VU probability of extinction
exceeds 0.10 over a century
24
).
A possible comparative technique could be to use taxa best known in both fossil and modern records: near-shore marine species with shells,
lowland terrestrial vertebrates (especially mammals), and some plants. This would require improved assessments of modern bivalves and
gastropods. Statistical techniques could be used to clarify how a subsample of well-assessed taxa extrapolates to undersampled and/or poorly
assessed taxa
25
.
Taxonomy
Analyses of fossils areoften done at the level of genus rather than species. When species are identifiedthey are usually based on a morphological
species concept. This can result in lumping species together that are distinct, or, if incomplete fossil material is used, over-splitting species. For
modern taxa, analyses are usually done at the level of species, often using a phylogenetic species concept, which probably increases species
counts relative to morphospecies.
A possible comparative technique would be to aggregate modern phylogenetic species into morphospecies or genera before comparing with the
fossil record.
Assessing extinction
Fossil extinction is recorded when a taxon permanently disappears from the fossil record and underestimates the actual number of extinctions (and
numberofspecies)becausemosttaxahavenofossilrecord.Theactualtimeof extinction almost always postdates the last fossil occurrence. Modern
extinction is recorded when no further individuals of a species are sighted after appropriate efforts. In the past few decades designation as ‘extinct’
usually follows IUCN criteria, which are conservative and likely to underestimate functionally extinct species
34
. Modern extinction is also
underestimated because many species are unevaluated or undescribed.
A possiblecomparativetechniquecould be to standardize extinctioncounts by numberof species knownper time interval of interest (proportional
extinction). However, fossil data demonstrate that background rates can varywidely from one taxonto the next
35,86,87
, so fossil-to-modern extinction
rate comparisons are most reliably done on a taxon-by-taxon basis, using well-known extant clades that also have a good fossil record.
Time
In the fossil record sparse samples of species are discontinuously distributed through vast time spans, from 10
3
to 10
8
years. In modern times we
have relatively dense samples of species over very short time spans of years, decades and centuries. Holocene fossils are becoming increasingly
available and valuable in linking the present with the past
48,90
.
A possible comparative technique would be to scale proportional extinction relative to the time interval over which extinction is measured.
RESEARCH REVIEW
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has been E/MSY (extinctions per million species-years, as defined in refs
15 and 27). In this approach, background rates are estimated from fossil
extinctions that took place in million-year-or-more time bins. For cur-
rent rates, the proportion of species extinct in a comparatively veryshort
time (one to a few centuries) is extrapolated to predict what the rate
would be over a million years. However, both theory and empirical data
indicate that extinction rates vary markedly depending on the length of
time over which they are measured
28,29
. Extrapolating a rate computed
over a short time, therefore, will probably yield a rate that is either much
faster or much slower than the average million-year rate, so current rates
that seem to be elevated need to be interpreted in this light.
Only recently has it become possible to do this by using palaeontology
databases
30,31
combined with lists of recently extinct species. The most
complete data set of this kind is for mammals, which verifies the efficacy
of E/MSY by setting short-interval and long-interval ratesin a comparative
context (Fig. 1). A data gap remains between about one million and about
50 thousand years because it is not yet possible to date extinctions in that
time range with adequate precision. Nevertheless, the overall pattern is as
expected: the maximum E/MSY and its variance increaseas measurement
intervals become shorter. The highest rates are rare but low rates are
common; in fact, at time intervals of less than a thousand years, the most
common E/MSY is 0. Three conclusions emerge. (1) The maximum
observed rates since a thousand years ago (E/MSY <24 in 1,000-year bins
to E/MSY <693 in 1-year bins) are clearly far above the average fossil rate
(about E/MSY <1.8), and even above those of the widely recognized late-
Pleistocene megafaunal diversity crash
32,33
(maximum E/MSY <9, red
data points in Fig. 1). (2) Recent average rates are also too high compared
to pre-anthropogenic averages: E/MSY increases to over 5 (and rises to
23) in less-than-50-year time bins. (3) In the scenario where currently
‘threatened’ species
34
would ultimately go extinct even in as much as a
thousand years, the resulting rates would far exceed any reasonable
estimation of the upper boundary for variation related to interval length.
The same applies if the extinction scenario is restricted to only ‘critically
endangered’ species
34
. This does not imply that we consider all species in
these categories to be inevitably destined for extinction—simply thatin a
worst-case scenariowhere that occurred, the extinction rate for mammals
would far exceed normal background rates. Because our computational
method maximizes the fossil background rates and minimizes the current
rates (see Fig. 1 caption),our observation that modern rates are elevatedis
likely to be particularly robust. Moreover, for reasons argued by others
27
,
the modern rates we computed probably seriously underestimate current
E/MSY values.
Another approach is simply to ask whether it is likely that extinction
rates could have been as high in many past 500-year intervals as they
have been in the most recent 500 years. Where adequate data exist, as is
the case for our mammal example, the answer is clearly no. The mean
per-million-year fossil rate for mammals we determined (Fig. 1) is about
1.8 E/MSY. To maintain that million-year average, there could be no
more than 6.3% of 500-year bins per million years (126 out of a possible
2,000) with an extinction rate as high as that observed over the past 500
years (80 extinct of 5,570 species living in 500 years). Million-year
extinction rates calculated by others, using different techniques, are
slower: 0.4 extinctions per lineage per million years (a lineage in this
context is roughly equivalent to a species)
35
. To maintain that slower
million-year average, there could be no more than 1.4% (28 intervals) of
the 500-year intervals per million years having an extinction rate as high
as the current 500-year rate. Rates computed for shorter time intervals
would be even less likely to fall within background levels, for reasons
noted by ref. 27.
Magnitude
Comparisons of percentage loss of species in historical times
6,36
to the
percentage loss that characterized each of the Big Five (Fig. 2) need to
be refinedby compensating for many differences between the modern and
the fossil records
2,37–39
. Seldom taken into account is the effect of using
different species concepts (Box 1), which potentially inflates the numbers
of modern species relative to fossil species
39,40
. A second, related caveat is
that most assessments of fossil diversity are at the level of genus, not
species
2,3,37,38,41
. Fossilspecies estimatesare frequentlyobtained by calculat-
ing the species-to-genus ratio determined for well-known groups, then
extrapolating that ratio to groups for which only genus-level counts exist.
The over-75% benchmark for mass extinction is obtained in this way
2
.
Table 2
|
Methods of comparing present and past extinctions
General method Variations and representative studies References
Compare currently measured extinction rates to
background rates assessed from fossil record
E/MSY*{7, 10, 15, 27, 62
Comparative species duration (estimates species durations to derive an
estimate of extinction rate)*{
14
Fuzzy Math*{44, 80
Interval-rate standardization (empirical derivation of relationship between
rate and interval length over which extinction is measured provides context
for interpreting short-term rates){
This paper
Use various modelling techniques, including
species-area relationships, to assess loss of species
Compare rate of expected near-term future losses to estimated background
extinction rates*{{
7, 10, 14, 15
Assess magnitude of past species losses{{42, 45
Predict magnitude of future losses. Ref. 7 explores several models and
provides a range of possible outcomes using different impact storylines{{
7, 14, 15, 27, 36, 62, 81–84
Compare currently measured extinction rates to
mass-extinction rates
Use geological data and hypothetical scenarios to bracket the range of
rates that could have produced past mass extinctions, and compare with
current extinction rates (assumes Big Five mass extinctions were sudden,
occurring within 500 years, producing a ‘worst-case scenario’ for high rates,
but with the possible exception of the Cretaceous event, it is unlikely that any
of the Big Five were this fast){
This paper
Assess extinction in context of long-term clade
dynamics
Map projected extinction trajectories onto long-term diversification/
extinction trends in well-studied clades{
This paper
Assess percentage loss of species Use IUCN lists to assess magnitude or rate of actual and potential species
losses in well-studied taxa{
This paper and refs 6, 7, 10,
14, 15, 20, 36 and 62
Use molecular phylogenies to estimate extinction rate Calculate background extinction rates from time-corrected molecular
phylogenies of extant species, and compare to modern rates
85
Fuzzy Math attempts to account for different biases in fossil and modern samples and uses empirically based fossil background extinction rates as a standard for comparison: 0.25 species per million years for
marine invertebrates, determined from the ‘kill-curve’ method
86
, and 0.21 species
35
to 0.46 species
87
per million years for North American mammals, determined from applying maximum-likelihood techniques.
The molecular phylogenies method assumes that diversification rates are constant through time and can be partitioned into originations and extinctions without evidence from the fossil record. Recent work has
demonstrated that disentanglement of diversification from extinction rates by this method is difficult, particularly in the absence of a fossil record, and that extinction rates estimated from molecular phylogenies of
extant organisms are highly unreliable when diversification rates vary among lineages through time
46,88
.
*Comparison of modern short-term rates with fossil long-term rates indicate highly elevated modern rates, but does not take into account interval-rate effect.
{Assumes that the relationship between number and kind of species lost in study area can be scaled up to make global projections.
{Assumes that conclusions from well-studied taxa illustrate general principles.
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Potentially valuable comparisons of extinction magnitude could come
from assessing modern taxonomic groups that are also known from
exceptionally good fossil records.The best fossil recordsare for near-shore
marine invertebrates like gastropods, bivalves and corals, and temperate
terrestrial mammals, with good information also available for Holocene
Pacific Island birds
2,33,35,42–44
. However, better knowledge of understudied
modern taxa is critically important for developing common metrics for
modern and fossil groups. Forexample, some 49% of bivalveswent extinct
during the end-Cretaceous event
43
, but only 1% of today’s species have
even been assessed
6
, making meaningful comparison difficult. A similar
problem prevails for gastropods, exacerbated because most modern
assessments are on terrestrial species, and most fossil data come from
marine species. Given the daunting challenge of assessing extinction risk
in every living species, statistical approaches aimed at understanding what
well sampled taxa tell us about extinction risks in poorly sampled taxa are
critically important
25
.
For a very few groups, modern assessments are close to adequate.
Scleractinian corals, amphibians, birds and mammals have all known
speciesassessed
6
(Fig. 2), although species counts remain a moving target
27
.
In these groups, even though the percentage of species extinct in historic
time is low (zero to 1%), 20–43% of their species and many more of their
populations are threatened (Fig. 2). Those numbers suggest that we have
not yet seen the sixth mass extinction, but that we would jump from one-
quarter to halfway towards it if ‘threatened’ species disappear.
Given that many clades are undersampled or unevenly sampled,
magnitude estimates that rely on theoretical predictions rather than
empirical data become important. Often species-area relationships or
allied modelling techniques are used to relate species losses to habitat-
area losses (Table 2). These techniques suggest that future species
extinctions will be around 21–52%, similar to the magnitudes expressed
Cycadopsida
Mammalia
Aves
Reptilia
Amphibia
Actinopterygii
Scleractinia
Gastropoda
Bivalvia
Coniferopsida
Chondrichthyes
Decapoda
Big Five mass
extinctions
0255075100
Extinction magnitude
(percentage of species)
Figure 2
|
Extinction magnitudes of IUCN-assessed taxa
6
in comparison to
the 75% mass-extinction benchmark. Numbers next to each icon indicate
percentage of species. White icons indicate species ‘extinct’ and ‘extinct in the
wild’ over the past 500 years. Black icons add currently ‘threatened’ species to
those already ‘extinct’ or ‘extinct inthe wild’; the amphibian percentage may be as
high as 43% (ref. 19). Yellow icons indicatethe Big Five species losses: Cretaceous
1Devonian, Triassic, Ordovician and Permian (from left to right). Asterisks
indicate taxa for whichvery few species (less than 3% forgastropodsand bivalves)
have beenassessed;white arrowsshow where extinction percentages are probably
inflated (because species perceived to be in peril are often assessed first). The
number ofspecies known or assessed for each of the groups listed is: Mammalia
5,490/5,490; Aves (birds) 10,027/10,027; Reptilia 8,855/1,677; Amphibia 6,285/
6,285, Actinopterygii 24,000/5,826, Scleractinia (corals) 837/837; Gastropoda
85,000/2,319; Bivalvia30,000/310,Cycadopsida307/307; Coniferopsida 618/618;
Chondrichthyes 1,044/1,044; and Decapoda 1,867/1,867.
10,000
1,000
100
10
1
0.1
0.01
0
10710610510410310210 1
Time-interval len
g
th (years)
E/MSY
Cenozoic
fossils
CR
EN
VU
CR
EN
VU CR
EN
VU
Pleistocene
Extinctions
since 2010
Minus bats
and endemics
Figure 1
|
Relationship between extinction rates and the time interval over
which the rates were calculated, for mammals. Each small grey datum point
represents the E/MSY (extinction per million species-years) calculated from
taxon durations recorded in the Paleobiology Database
30
(million-year-or-
more time bins) or from lists of extant, recently extinct, and Pleistocene species
compiled from the literature (100,000-year-and-less time bins)
6,32,33,89–97
.More
than 4,600 data points are plotted and cluster on top of each other. Yellow
shading encompasses the ‘normal’ (non-anthropogenic) range of variance in
extinction rate that would be expected given different measurement intervals;
for more than 100,000 years, it is the same as the 95% confidence interval, but
the fading to the right indicates that the upper boundary of ‘normal’ variance
becomes uncertain at short time intervals. The short horizontal lines indicate
the empirically determined mean E/MSY for each time bin. Large coloured dots
represent the calculated extinction rates since 2010. Red, the end-Pleistocene
extinction event. Orange, documented historical extinctions averaged (from
right to left) over the last 1, 30, 50, 70, 100, 500, 1,000 and 5,000 years. Blue,
attempts to enhance comparability of modern with fossil data by adjusting for
extinctions of species with very low fossilization potential (such as those with
very small geographic ranges and bats). For these calculations, ‘extinct’ and
‘extinct in the wild’ species that had geographic ranges less than 500km
2
as
recorded by the IUCN
6
, all species restrictedto islands of less than 105 km
2
, and
bats were excluded from the counts (under-representation of bats as fossils is
indicated by their composing only about 2.5% of the fossil species count, versus
around 20% of the modern species count
30
). Brown triangles represent the
projections of rates that would result if ‘threatened’ mammals go extinct within
100, 500 or 1,000years. The lowest triangle (of each vertical set) indicates the
rate if only ‘critically endangered’ species were to go extinct (CR), the middle
triangle indicates the rate if ‘critically endangered’ 1‘endangered’ species were
to go extinct (EN), and the highest triangle indicates the rate if ‘critically
endangered’ 1‘endangered’ 1‘vulnerable’ species were to go extinct (VU). To
produce Fig. 1 we first determined the last-occurrence records of Cenozoic
mammals from the Paleobiology Database
30
, and the last occurrences of
Pleistocene and Holocene mammals from refs 6, 32, 33 and 89–97. We then
used R-scripts (written by N.M.) to compute total diversity, number of
extinctions, proportional extinction, and E/MSY (and its mean) for time-bins
of varying duration. Cenozoic time bins ranged from 25 million to a million
years. Pleistocene time bins ranged from 100,000 to 5,000 years, and Holocene
time bins from 5,000years to a year. For Cenozoic data, the mean E/MSY was
computed using the average within-bin standing diversity, which was
calculated by counting all taxa that cross each 100,000-year boundary within a
million-year bin, then averaging those boundary-crossing counts to compute
standing diversity for the entire million-year-and-over bin. For modern data,
the mean was computed using the total standing diversity in each bin (extinct
plus surviving taxa). This method may overestimate the fossil mean extinction
rate and underestimate the modernmeans, so it is a conservative comparison in
terms of assessing whethermodern means are higher. The Cenozoic data are for
North America and the Pleistoceneand Holocene data are for global extinction;
adequate global Cenozoic data are unavailable. There is no apparent reason to
suspect that the North American average would differ from the global average
at the million-year timescale.
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©2011
in Fig. 2, although derived quite differently. Such models may be sensi-
tive to the particular geographic area, taxa and species-area relationship
that is employed, and have usually used only modern data. However,
fossil-to-modern comparisons using species-area methods are now
becoming possible as online palaeontological databases grow
30,31,45
.An
additional, new approach models how much extinction can be expected
under varying scenarios of human impact
7
. It suggests a broader range of
possible future extinction magnitudes than previous studies, although
all scenarios result in additional biodiversity decline in the twenty-first
century.
Combined rate–magnitude comparisons
Because rate and magnitude are so intimately linked, a critical question is
whether current rates would produce Big-Five-magnitude mass extinc-
tions in the same amount of geological time that we think most Big Five
extinctions spanned (Table 1). The answer is yes (Fig. 3). Current extinc-
tion rates for mammals, amphibians, birds, and reptiles (Fig. 3, light
yellow dots on the left), if calculated over the last 500 years (a conserva-
tively slow rate
27
) are faster than (birds, mammals, amphibians, which
have 100% of species assessed) or as fast as (reptiles, uncertain because
only 19% of species are assessed) all rates that would have produced the
Big Five extinctions over hundreds of thousands or millions of years
(Fig. 3, vertical lines).
Would rates calculated for historical and near-time prehistoric
extinctions result in Big-Five-magnitude extinction in the foreseeable
future—less than a few centuries? Again, taking the 500-year rate as a
useful basis of comparison, two different hypothetical approaches are
possible. The first assumes that the Big Five extinctions took place
suddenly and asks what rates would have produced their estimated
species losses within 500 years (Fig. 3, coloured dots on the right).
(We emphasize that this is a hypothetical scenario and that we are not
arguing that all mass extinctions were sudden.) In that scenario, the rates
for contemporary extinctions (Fig. 3, light yellow dots on the left) are
slower than the rates that would have produced each of the Big Five
extinctions in 500 years. However,rates that consider ‘threatened’ species
as inevitably extinct (Fig. 3, orange dots on the left) are almost as fast as
the 500-year Big Five rates. Therefore, at least as judged using these
vertebrate taxa, losing threatened species would signal a mass extinction
nearly on par with the Big Five.
A second hypothetical approach asks how many more years it would
take for currentextinction rates to producespecies losses equivalentto Big
Five magnitudes. The answer is that if all ‘threatened’ species became
extinct withina century, and that rate then continued unabated,terrestrial
amphibian, bird and mammal extinction would reach Big Five magni-
tudes in ,240 to 540 years (241.7 years for amphibians, 536.6 years for
birds, 334.4years for mammals). Reptiles have so few of their species
assessed that they are not included in this calculation. If extinction were
limited to ‘critically endangered’ species over the next century and those
extinction rates continued, the time until 75% of species were lost per
group would be 890 years for amphibians, 2,265 years for birds and
1,519 years for mammals. For scenarios that project extinction of
‘threatened’ or ‘critically endangered’ species over 500 years instead of
a century, mass extinction magnitudes would be reached in about 1,200
to 2,690 years for the ‘threatened’ scenario (1,209 years for amphibians,
2,683 years for birds and 1,672 years for mammals) or ,4,450 to 11,330
years for the ‘critically endangered’ scenario (4,452 years for amphi-
bians, 11,326 years for birds and 7,593 years for mammals).
This emphasizes that current extinction rates are higher than those that
caused Big Five extinctions in geological time; they could be severe enough
to carry extinction magnitudes to the Big Five benchmark in as little as t hree
centuries. It also highlights areas for much-needed future research. Among
major unknowns are (1) whether ‘critically endangered’, ‘endangered’ and
‘vulnerable’ species will go extinct, (2) whether the current rates we used in
our calculations will continue, increase or decrease; and (3) how reliably
extinction rates in well-studied taxa can be extrapolated to other kinds of
species in other places
7,20,25,34
.
The backdrop of diversity dynamics
Little explored is whether current extinction rates within a clade fall out-
side expectations when considered in the context of long-term diversity
dynamics. For example, analyses of cetacean (whales and dolphins)
extinction and origination rates illustrate that within-clade diversity has
been declining for the last 5.3 million years, and that that decline is nested
within an even longer-term decline that began some 14 million years ago.
Yet, within that context, even if ‘threatened’ genera lasted as long as
100,000years before going extinct, the clade would still experience an
extinction rate that is an order of magnitude higher than anything it has
experienced during its evolutionary history
46
.
The fossil record is also enabling us to interpret better the significance
of currently observed population distributions and declines. The use of
ancient DNA, phylochronology and simulations demonstrate that the
population structure considered ‘normal’ on the current landscape has
in fact already suffered diversity declines relative to conditions a few
thousand years ago
47,48
. Likewise, the fossil record shows that species
richness and evenness taken as ‘normal’ today are low compared to pre-
anthropogenic conditions
10,27,32,33,42,45,49
.
Selectivity
During times of normal background extinction, the taxa that suffer
extinction most frequently are characterized by small geographic ranges
and low population abundance
38
. However, during times of mass extinc-
tion, the rules of extinction selectivity can change markedly, so that
widespread, abundant taxa also go extinct
37,38
. Large-bodied animals
and those in certain phylogenetic groups can be particularly hard
hit
33,50–52
. In that context, the reduction of formerly widespread ranges
8
and disproportionate culling of certain kinds of species
50–53
may be
E/MSY
1,000,000
10
100
1
0.1
1,000
10,000
100,000
Devonian
Cretaceous
TH, CR
Triassic
Ordovician
Permian
0.01
Extinction ma
g
nitude (percenta
g
e of species)
0 20 406080100
Critically
endangered
Already
extinct Threatened
Figure 3
|
Extinction rate versus extinction magnitude. Vertical lines on the
right illustrate the range of mass extinction rates (E/MSY) that would produce
the Big Five extinction magnitudes, as bracketed by the best available data from
the geological record. The correspondingly coloured dots indicate what the
extinction rate would have been if the extinctions had happened
(hypothetically) over only 500 years. On the left, dots connected by lines
indicate the rate as computed for the past 500years for vertebrates: light yellow,
species already extinct; dark yellow, hypothetical extinction of ‘critically
endangered’ species; orange, hypothetical extinction of all ‘threatened’ species.
TH: if all ‘threatened’ species became extinct in 100 years, and that rate of
extinction remained constant, the time to 75% species loss—that is, the sixth
mass extinction—would be ,240 to 540 years for those vertebrates shown here
that have been fully assessed (all but reptiles). CR: similarly, if all ‘critically
endangered’ species became extinct in 100 years, the time to 75% species loss
would be ,890 to 2,270 years for these fully assessed terrestrial vertebrates.
REVIEW RESEARCH
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©2011
particularly informative in indicating that extinction-selectivity is chan-
ging into a state characterizing mass extinctions.
Perfect storms?
Hypotheses to explain the general phenomenon of mass extinctions
have emphasized synergies between unusual events
54–57
. Common fea-
tures of the Big Five (Table 1) suggest that key synergies may involve
unusual climate dynamics, atmospheric composition and abnormally
high-intensity ecological stressors that negatively affect many different
lineages. This does not imply that random accidents like a Cretaceous
asteroid impact
58,59
would not cause devastating extinction on their own,
only that extinction magnitude would be lower if synergistic stressors
had not already ‘primed the pump’ of extinction
60
.
More rigorously formulating and testing synergy hypotheses may be
especially important in assessing sixth mass extinction potential,
because once again the global stage is set for unusual interactions.
Existing ecosystems are the legacy of a biotic turnover initiated by the
onset of glacial–interglacial cycles that began ,2.6 million years ago,
and evolved primarily in the absence of Homo sapiens. Today, rapidly
changing atmospheric conditions and warming above typical interglacial
temperatures as CO
2
levels continue to rise, habitat fragmentation, pol-
lution, overfishing and overhunting, invasive species and pathogens (like
chytrid fungus), and expanding human biomass
6,7,18,20
are all more
extreme ecological stressors than most living species have previously
experienced. Without concerted mitigation efforts, such stressors will
accelerate in the future and thus intensify extinction
7,20
, especially given
the feedbacks between individual stressors
56
.
View to the future
There is considerably more to be learned by applying new methods that
appropriatelyadjust for the different kindsof data and timescales inherent
in the fossil records versus modern records. Future work needs to: (1)
standardizerate comparisons to adjust for rate measurements over widely
disparate timescales; (2) standardize magnitude comparisonsby using the
same species (or other taxonomic rank) concepts for modern and fossil
organisms; (3) standardize taxonomic and geographic comparisons by
using modern and fossil taxa that have equal fossilization potential; (4)
assess the extinction risk of modern taxa such as bivalves and gastropods
that are extremely common in the fossil record but are at present poorly
assessed; (5) set current extinction observations in the context of long-
term clade, species-richness, and population dynamics using the fossil
record and phylogenetic techniques; (6) further explore the relationship
between extinction selectivity and extinction intensity; and (7) develop
and test modelsthat posit general conditions requiredfor mass extinction,
and how those compare with the current state of the Earth.
Our examination of existing datain these contexts raises twoimportant
points. First, the recent loss of species is dramatic and serious but does not
yet qualify as a mass extinction in the palaeontological sense of the Big
Five. In historic times we have actually lost only a few per cent of assessed
species (though we have no way of knowing how many species we have
lost that had never been described). It is encouraging that there is still
much of the world’s biodiversity left to save, but daunting that doing so
will require the reversal of many dire and escalating threats
7,20,61–63
.
The second point is particularly important. Even taking into account
the difficulties of comparing the fossil and modern records, and applying
conservative comparative methods that favour minimizing the differ-
ences between fossil and modern extinction metrics, there are clear indi-
cations that losing species now in the ‘critically endangered’ category
would propel the world to a state of mass extinction that has previously
been seen only five times in about 540 million years. Additional losses of
species in the ‘endangered’ and ‘vulnerable’ categories could accomplish
the sixth mass extinction in just a few centuries. It may be of particular
concern that this extinction trajectory would play out under conditions
that resemble the ‘perfect storm’ that coincided with past mass extinc-
tions: multiple, atypical high-intensity ecological stressors, including
rapid, unusual climate change and highly elevated atmospheric CO
2
.
The huge difference between where we are now, and where we could
easily be within a few generations, reveals the urgency of relieving the
pressures that are pushing today’s species towards extinction.
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Acknowledgements S. Beissinger, P. Ehrlich, E. Hadly, A. Hubbe,D. Jablonski, S. Pimm
and D. Wake provided constructive comments. Paleobiology Database data were
contributed by M. Carrano, J. Alroy, M. Uhen, R. Butler, J. Mueller, L. van den Hoek
Ostende, J. Head,E. Fara, D. Croft, W. Clyde, K. Behrensmeyer, J. Hunter,R. Whatley and
W. Kiessling. The work was funded in part by NSF grants EAR-0720387 (to A.D.B.) and
DEB-0919451 (supporting N.M.). This is University of California Museum of
Paleontology Contribution 2024.
Author Contributions All authors participated in literature review and contributed to
discussions that resulted in this paper. A.D.B. planned the project, analysed and
interpreted data, and wrote the paper. N.M. and S.T. performedkey data analyses and
interpretation relating to rate comparisons. G.O.U.W., B.S. and E.L.L. assembled critical
data. T.B.Q. and C.M. provided data, analyses and ideas relating to diversity dynamics
and rate-magnitude comparisons. J.L.M. helped produce figures and with N.M., S.T.,
G.O.U.W., B.S., T.B.Q., C.M., K.C.M., B.M. and E.A.F. contributed to finalizing the text.
Author Information Reprints and permissions information is available at
www.nature.com/reprints. The authors declare no competing financial interests.
Readers are welcome to comment on the online version of this article at
www.nature.com/nature. Correspondence should be addressed to A.D.B.
(barnosky@berkeley.edu).
REVIEW RESEARCH
3MARCH2011|VOL471|NATURE|57
Macmillan Publishers Limited. All rights reserved
©2011
... The loss of biodiversity due to human-driven agricultural expansion, logging and development has caused major concerns for species declines, with extinction rates increased to similar levels of the last five global mass-extinction events over the last 500 million years (Barnosky et al., 2011;Tilman et al., 2017). Agricultural practices have been reported to occupy 40% of Earth's land surface Mclaughlin, 2011), with even higher percentages in Europe, where the UK classifies 71% of its land as agriculture (DEFRA, 2014). ...
... The loss of biodiversity due to human-driven agricultural expansion, logging and development has caused major concerns for species declines, with extinction rates increasing to similar levels of the last five global mass-extinction events in the last 500 million years (Barnosky et al., 2011;Tilman et al., 2017). Agriculture threatens more species than any other human activity Tilman et al., 2017). ...
Thesis
In this thesis I assess the ability of biodiversity to provide a functioning pest control ecosystem service to control moth pest species in UK apple orchards. I assess the ability of four types of farm management: organic, Linking Environment and Farming (LEAF), integrated pest management (IPM) and conventional, to measure the ability of pest predation from birds, and the impact that predation has on apple yields. I firstly describe the history and the landscape of the study area, an overview of the methods used and the farming systems that the field study and experiments took place on in Chapter 2. In Chapter 3 I assess farmland biodiversity by monitoring birds and butterflies as indicator species of biodiversity, to understand if farm management impacts biodiversity levels. Biodiversity was highest on organic orchards, which supports the plethora of studies in the literature. Using this information of biodiversity levels on orchard management types, in Chapter 4 I investigate whether this biodiversity supports a pest control service, and to a natural pest control service compares to a synthetic alternate used on non-organic orchards, through using a sentinel prey experiment in field. Pest control services were greater on organic farms, and followed the same patterns as insectivorous bird abundance, species richness, diversity, and density. This chapter also compares moth pest levels to understand the pest pressures across farms, which harbour different pest control strategies and showed that moth pest levels were broadly similar across all farm management types. Finally, in Chapter 5 I compare the farm management options available to famers, both the natural pest control system and the synthetic control system, using economic valuation methods. Although a natural pest control service from birds is present on organic orchards (Chapter 4), the yield per hectare increased significantly on non-organic orchards (expect LEAF) but is found to be in-different to yield value per hectare of organic orchards in variable scenarios. Importantly, the synthetic alternative to a pest control service available from wild insectivorous birds was found to be an insignificant farm management variable that impacts apple yield and yield value on non-organic orchards.
... Malgré cette prise de conscience et l'essor de la biologie de la conservation, les pressions subies par la biodiversité ne cessent de s'intensifier. Les paléontologues définissent une extinction de masse lorsque la Terre voit disparaître les trois quarts des espèces qui la colonisent, sur une courte période à l'échelle des temps géologiques (Barnosky et al., 2011;Twitchett, 2006). Au cours de l'histoire de la Terre, cinq extinctions massives ont eu lieu, dont la dernière a causé l'extinction de la plupart des dinosaures à la fin du Crétacé, il y a environ 66 millions d'années (Jablonski, 1989 (Ceballos et al., 2017;Dirzo and Raven, 2003;Jablonski, 1989). ...
... Au cours de l'histoire de la Terre, cinq extinctions massives ont eu lieu, dont la dernière a causé l'extinction de la plupart des dinosaures à la fin du Crétacé, il y a environ 66 millions d'années (Jablonski, 1989 (Ceballos et al., 2017;Dirzo and Raven, 2003;Jablonski, 1989). Beaucoup de scientifiques suggèrent donc qu'une sixième extinction de masse est en cours (Barnosky et al., 2011;Cafaro, 2015;Wake and Vredenburg, 2008), principalement induite par les activités anthropiques, de façon directe, par la réduction des habitats, la surexploitation, la pollution, l'introduction d'espèces invasives, la propagation de pathogènes, etc., ou indirecte à travers le changement climatique (Baillie et al., 2004;Ceballos et al., 2015;Hoffmann et al., 2010;Pievani, 2014). L'extinction d'une espèce n'est généralement pas immédiate et se traduit par le déclin progressif de ses populations conduisant à la perte de diversité génétique (Ceballos et al., 2017). ...
Thesis
Les systèmes marins côtiers sont généralement discontinus et constitués d’une mosaïque de paysages sous-marins différents, créant ainsi des distributions parfois très fragmentées chez les espèces qui les colonisent. Les espèces marines côtières sont donc structurées en réseaux de populations connectées entre elles via la dispersion larvaire. Comprendre le fonctionnement et la connectivité entre les populations d’une espèce est indispensable pour adapter les stratégies de conservation. La grande nacre, Pinna nobilis, est une espèce endémique de la mer Méditerranée qui fait aujourd’hui face à une crise majeure qui menace sa survie. Depuis Octobre 2016, des mortalités de masse sont signalées sur ses populations, à travers toutes la mer Méditerranée, causées par un protozoaire parasite, Haplosporidium pinnae. Il s’agit d’un évènement sans précédent, que ce soit par le taux de mortalité (près de 100 %) ou la vitesse de propagation, et qui pourrait conduire à l’extinction de l’espèce. En se focalisant sur le littoral Occitan, cette thèse apporte des connaissances sur la biologie et l’écologie de l’espèce mais aussi sur son fonctionnement et les processus qui permettent le maintien de ses populations afin de proposer des priorités de conservation. Ainsi, nous avons mis en évidence la diversité d’habitats colonisés par l’espèce ainsi que l’importance des lagunes car elles abritent près de 90 % des grandes nacres, sur le littoral Occitan, et semblent servir d’habitat refuge à l’espèce en limitant l’infestation par le parasite. A l’aide de marqueurs microsatellites nouvellement développés, nous avons montré une structure génétique très homogène sur toute la côte, ce qui implique un certain niveau de connectivité et laisse penser qu’une grande partie de la diversité génétique de l’espèce reste préservée dans les lagunes. En se focalisant sur la population de la baie de Peyrefite, dans la Réserve Naturelle Marine de Cerbère-Banyuls, et grâce à une analyse de parenté, nous avons apporté des connaissances sur la dynamique démographique et les processus de repeuplement de l’espèce. L’ensemble de cette thèse permet de définir des recommandations qui seront utiles à la mise en place de mesures de conservation adaptées, indispensables pour la survie de l’espèce.
... Despite their relative resilience to extinction, small mammal community composition may be altered by environmental change and human impacts in other, less obvious ways. Extinctions are the most dramatic and conspicuous losses of diversity and are therefore the focus of many studies on biodiversity decline in the Anthropocene (e.g., Barnosky et al., 2011). However, reductions in population and community-level diversity may reveal declines in ecosystem stability and may precede and predict extinctions (Blois et al., 2010;Ceballos et al., 2017). ...
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The multi-faceted impacts of the Anthropocene are increasingly modifying natural ecosystems and threatening biodiversity. Can small protected spaces conserve small mammal diversity across spatial and temporal scales of human impact? We identified small mammal remains from modern raptor pellets and Holocene archeological sites along a human modification gradient in the San Francisco Bay Area, CA and evaluated alpha and beta diversity across sites and time periods. We found that Shannon diversity, standardized species richness, and evenness decrease across modern sites based on level of human modification, with no corresponding change between Holocene sites. Additionally, the alpha diversity of modern sites with moderate and high levels of human modification was significantly lower than the diversity of modern sites with low levels of human modification as well as all Holocene sites. On the other hand, the small mammal communities from Jasper Ridge Biological Preserve, a small protected area, retain Holocene levels of alpha diversity. Jasper Ridge has also changed less over time in terms of overall community composition (beta diversity) than more modified sites. Despite this, Holocene and Anthropocene communities are distinct regardless of study area. Our results suggest that small mammal communities today are fundamentally different from even a few centuries ago, but that even relatively small protected spaces can partially conserve native faunal communities, highlighting their important role in urban conservation.
... Human activities are causing a global biodiversity crisis, with species disappearing at rates that are up to 1000 times higher than that in the fossil record (Barnosky et al., 2011). In particula r, over 600 vertebrate species have possibly gone extinct in the last half millennium, marking the arrival of the sixth mass extinction (Pimm et al., 2014;Ceballos et al., 2015). ...
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Despite that cetaceans provide significant ecological contributions to the health and stability of aquatic ecosystems, they are highly endangered with nearly one-third of species assessed as threatened with extinction. Nevertheless, to date, few studies have explicitly examined the patterns and processes of extinction risk and threats for this taxon, and even less between the two subclades (Mysticeti and Odontoceti). To fill this gap, we compiled a dataset of six intrins ic traits (active region, geographic range size, body weight, diving depth, school size and reproductive cycle), six environmental factors relating to sea surface temperature and chlorophyll concentration, and two human-related threat indices that are commonly recognized for cetaceans. We then employed phylogenetic generalized least square (PGLS) models and model selection to identify the key predictors of extinction risk in all cetaceans, as well as in the two subclades. We found that geographic range size, sea surface temperature and human threat index were the most important predictors of extinction risk in all cetaceans and in odontocetes. Interestingly, maximum body weight was positively associated with the extinction risk in mysticetes, but negatively related to that for odontocetes. By linking seven major threat types to extinction risk, we further revealed that fisheries bycatch was the most common threat, yet the impacts of certain threats could be overestimated when considering all species rather than just threatened ones. Overall, we suggest that conservation efforts should focus on small-ranged cetaceans and species living in warmer waters or under strong anthropogenic pressures. Moreover, further studies should consider the extinction risk of species when superimposing risk maps and quantifying risk severity. Finally, we emphasize that mysticetes and odontocetes should be conserved with different strategies, because their extinction risk patterns and major threat types are considerably different. For instance, large-bodied mysticetes and small-ranged odontocetes require special conservation priority.
... Some researchers (Alekseiev, 2000) qualify modern and still ongoing mass extinction, the consequences of which can be catastrophic both for the biosphere and for our civilisation. The known loss of species over the last few centuries and millennia has led biologists to speculate that the sixth mass extinction in Earth's history is now occurring (Barnosky et al., 2011).The issue of global climate change is widely debated in scientific, public and political circles. What are its main reasons: human industrial activity or natural factors? ...
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The outcrops of carbonate and siliceous rock horizons at the boundary of Eocene and Oligocene deposits in the Ukrainian Carpathians represent potential sites for geotourism. They are located in the northern part of the Skyba zone, in settlements (Boryslav, Verkhne Synyovydne, Maydan, Skole) that can be reached by various vehicles. The sites are of interest not only due to the possibility to be shown for tourists in situbut also due to the possibility to tell them about sedimentological history of the Carpathians, the whole Tethys basin and theWorld Ocean being the reason fortheir formation. The article considers global and regional events at the Eocene-Oligocene boundary, exemplified by deposits of the Sheshory horizon and lower siliceous horizon of the Lower Menilite Sub-Formation as well as sedimentologicaland lithogenetic aspects of chertsorigin.In sections of the Carpathian flysch the clay-calcareous and siliceous- clay rocks of the Sheshory (Eocene) and Rybnyk (Oligocene) horizons are overlaid by a pack of carbon-bearing cherts(mainly phthanites) of the Menilite Formationlower siliceous horizon. This was fixed as the «Eocene final event» (climatic cooling, mass extinction of some groups of marine organisms, including certain types of warm-water foraminifera), and had a global significance. At that time at the regional scale separation of the Paratethys Sea from the Tethys Ocean as well as sharp change in biogenic sedimentation (from carbonate to siliceous) in the Carpathian sedimentary basin occurred.At the Eocene and Oligocene boundary and then during the Oligocene the World Ocean demonstrated a series of events that ultimately led to the transformation of a global system of ocean waters circulation from the Cretaceous-Eocene, marked with uniformly warm climate throughout the planet, to contemporary with more contrast climate and distinct climatic zones.The change of warm-water plankton organisms for those who areaccustomed to live in cold seas can be illustrated by the results of study of calcareous and siliceous rocks of the Eocene-Oligocene deposits in the Ukrainian Carpathians.The Sheshory horizon marls are composed of cryptocrystalline clay- carbonate matter with numerous remains of warm-water forms of planctonic foraminifera from a group of globigerina (Globigerinida) sized up to 0.1 mm. The number and size of these organisms significantly reduced in the rocks of Rybnyk horizon. No Their traces are notfound in siliceous formations.Various researchers have justified biogenic, volcanogenic, or chemogenic origin of these cherts. Authors of the article believe that these rocks are the product of sedimentation of biogenic siliceous deposits and their post-sedimentary transformation.
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The exploration and use of wild plant resources goes back to our rooted history of human civilization over about 20,000 years ago, before Ancient Mesopotamia in the Valley of the Tigris and Euphrates where barley, lentil and wheat were first domesticated [...]
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Book
"Near time" -an interval that spans the last 100,000 years or so of earth history-qualifies as a remarkable period for many reasons. From an anthropocentric point of view, the out­ standing feature of near time is the fact that the evolution, cultural diversification, and glob­ al spread of Homo sapiens have all occurred within it. From a wider biological perspective, however, the hallmark of near time is better conceived of as being one of enduring, repeat­ ed loss. The point is important. Despite the sense of uniqueness implicit in phrases like "the biodiversity crisis," meant to convey the notion that the present bout of extinctions is by far the worst endured in recent times, substantial losses have occurred throughout near time. In the majority of cases, these losses occurred when, and only when, people began to ex­ pand across areas that had never before experienced their presence. Although the explana­ tion for these correlations in time and space may seem obvious, it is one thing to rhetori­ cally observe that there is a connection between humans and recent extinctions, and quite another to demonstrate it scientifically. How should this be done? Traditionally, the study of past extinctions has fallen largely to researchers steeped in such disciplines as paleontology, systematics, and paleoecology. The evaluation of future losses, by contrast, has lain almost exclusively within the domain of conservation biolo­ gists. Now, more than ever, there is opportunity for overlap and sharing of information.
Article
The extent to which human activity has influenced species extinctions during the recent prehistoric past remains controversial due to other factors such as climatic fluctuations and a general lack of data. However, the Holocene (the geological interval spanning the last 11,500 years from the end of the last glaciation) has witnessed massive levels of extinctions that have continued into the modern historical era, but in a context of only relatively minor climatic fluctuations. This makes a detailed consideration of these extinctions a useful system for investigating the impacts of human activity over time. This book describes and analyses the range of global extinction events which have occurred during this key time period, as well as their relationship to both earlier and ongoing species losses. By integrating information from fields as diverse as zoology, ecology, palaeontology, archaeology, and geography, and by incorporating data from a broad range of taxonomic groups and ecosystems, this text provides a fascinating insight into human impacts on global extinction rates, both past and present.
Chapter
Time series of global diversity and extinction intensity measured from data on stratigraphic ranges of marine animal genera show the impact of bio-events on the fauna of the world ocean. Measured extinction intensities vary greatly, from major mass extinctions that eradicated 39 to 82% of generic diversity to smaller events that had substantially less impact on the global fauna. Many of the smaller extinction events are clearly visible only after a series of filters are applied to the data. Still, most of these extinction events are also visible in a smaller set of data on marine families. Although many of the episodes of extinction seen in the global data are well known from detailed biostratigraphic investigations, some are unstudied and require focused attention for confirmation or refutation.
Article
Abstract? Biodiversity, a central component of Earth's life support systems, is directly relevant to human societies. We examine the dimensions and nature of the Earth's terrestrial biodiversity and review the scientific facts concerning the rate of loss of biodiversity and the drivers of this loss. The estimate for the total number of species of eukaryotic organisms possible lies in the 5?15 million range, with a best guess of ?7 million. Species diversity is unevenly distributed; the highest concentrations are in tropical ecosystems. Endemisms are concentrated in a few hotspots, which are in turn seriously threatened by habitat destruction?the most prominent driver of biodiversity loss. For the past 300 years, recorded extinctions for a few groups of organisms reveal rates of extinction at least several hundred times the rate expected on the basis of the geological record. The loss of biodiversity is the only truly irreversible global environmental change the Earth faces today.
Article
Near the end of the Late Ordovician, in the first of five mass extinctions in the Phanerozoic, about 85% of marine species died. The cause was a brief glacial interval that produced two pulses of extinction. The first pulse was at the beginning of the glaciation, when sea-level decline drained epicontinental seaways, produced a harsh climate in low and mid-latitudes, and initiated active, deep-oceanic currents that aerated the deep oceans and brought nutrients and possibly toxic material up from oceanic depths. Following that initial pulse of extinction, surviving faunas adapted to the new ecologic setting. The glaciation ended suddenly, and as sea level rose, the climate moderated, and oceanic circulation stagnated, another pulse of extinction occurred. The second extinction marked the end of a long interval of ecologic stasis (an Ecologic-Evolutionary Unit). Recovery from the event took several million years, but the resulting fauna had ecologic patterns similar to the fauna that had become extinct. Other extinction events that eliminated similar or even smaller percentages of species had greater long-term ecologic effects.