In the light of evolution II: Biodiversity and extinction
John C. Avise*?, Stephen P. Hubbell?, and Francisco J. Ayala*?
*Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697; and ?Department of Ecology
and Evolutionary Biology, University of California, Los Angeles, CA 90095
T
he Earth?s biodiversity is a well-
spring for scientific curiosity
about nature?s workings. It is
also a source of joy and inspira-
tion for inquisitive minds, from poets to
philosophers, and provides life-support
services. According to Kellert (2), biodi-
versity affords humanity nine principal
types of benefit: utilitarian (direct eco-
nomic value of nature?s goods and ser-
vices), scientific (biological insights),
aesthetic (inspiration from nature?s
beauty), humanistic (feelings deeply
rooted in our inherent attachment to
other species), dominionistic (physical
and mental well-being promoted by
some kinds of interactions with nature),
moralistic (including spiritual uplifting),
naturalistic (curiosity-driven satisfaction
from the living world), symbolic (nature-
stimulated imagination, communication,
and thought), and even negativistic
(fears and anxieties about nature, which
can actually enrich people?s life experi-
ence). Whether or not this list properly
characterizes nature?s benefits, the fact
is that a world diminished in biodiversity
would be greatly impoverished.
Many scientists have argued that, as a
consequence of human activities, the
Earth has entered the sixth mass extinc-
tion episode (and the only such event
precipitated by a biotic agent) in its
4-billion-year history (3, 4). The last cat-
astrophic extinction, which occurred

65 million years ago and was the coup-
de-grace for non-avian dinosaurs, marine
ammonites, and many other evolution-
ary lineages, happened rather suddenly
after a large asteroid slammed into the
planet. Today, most of the biotic holo-
caust is due?directly or indirectly?to
local, regional, and global environmen-
tal impacts from a burgeoning human
population. The first phase of the cur-
rent extinction episode started 
50,000?
100,000 years ago, when modern
humans began dispersing around the
planet. The second phase started 10,000
years ago with further population in-
creases and land-use changes associated
with the invention of agriculture. A
third phase of environmental alteration
and biodiversity loss was ushered in by
the industrial revolution. E. O. Wilson
(5) estimated that the Earth is currently
losing 
0.25% of its remaining species
per year (such that at least 12,000 spe-
cies may be going extinct annually).
Such estimates are educated guesses be-
cause they represent extrapolations
(from species-area curves and other evi-
dence) to taxa that undoubtedly are
disappearing even before they can be
identified and studied. Nevertheless,
they do reveal the general magnitude of
the ongoing extinction crisis. For many
species that manage to avoid extirpation,
local and regional populations are being
decimated.
The modern extinction crisis is
prompting scientific efforts on many
fronts. Systematists are striving to de-
scribe biodiversity and reconstruct the
Tree of Life. Ecologists are mapping the
distributions of biodiversity and global
hotspots that merit special conservation
attention. Paleontologists are placing the
current crisis in temporal context with
regard to the Earth?s long geological
history, and also to the recent history of
human impacts on biodiversity across
timescales ranging from decades to mil-
lennia. Educators and concerned scien-
tists are striving to alert government
leaders, policy makers, and the public to
the biodiversity crisis. Conservation ef-
forts (including those by many nongov-
ernment organizations) are underway to
slow the pace of biological extinctions.
However, unless conservation achieve-
ments accelerate quickly, the outlook
for biodiversity in and beyond the 21st
century remains grim.
The goals of this Colloquium were to
synthesize recent scientific information
and ideas about the abundance and dis-
tribution of biodiversity and to compare
contemporary biodiversity and extinc-
tion patterns with those in the distant
and near evolutionary past as well as
with those plausible in the near-term
future. Articles from the Colloquium
address biodiversity and extinction in
four contexts: Contemporary Patterns
and Processes in Animals; Contemporary
Patterns and Processes in Plants and
Microbes; Trends and Processes in the
Paleontological Past; and Prospects for
the Future.
Contemporary Patterns and Processes
in Animals
There is no doubt that humans are the
root cause of most ecosystem stresses
and biotic extinctions in the modern
world. Negative human pressures on
biodiversity occur via pollution, intro-
ductions of alien species, overexploita-
tion, landscape transformations, and
other factors. Like the asteroid impact
65 million years ago, human impacts
extend to many kinds of terrestrial,
aquatic, and marine organisms. The arti-
cles under this heading, and the next,
illustrate some of the challenges of
quantifying the magnitude of extant
biodiversity and deciphering extinction
rates and patterns in a representative
selection of diverse contemporary
biotas.
Oceans cover three-quarters of the
Earth?s surface, and their inhabitants
might seem at first thought to be some-
what buffered (compared with terrestrial
and freshwater species) against anthro-
pogenic disturbance. However, Jeremy
Jackson (6) compiles evidence from four
major marine realms?estuaries and
coastal areas, continental shelves, open
ocean pelagic zone, and coral reefs?
that marine ecosystems are under ex-
treme duress from the oft-synergistic
effects of habitat destruction, overfish-
ing, introduced species, warming and
acidification, toxins, and nutrient runoff.
One common result has been the degra-
dation of biodiverse marine ecosystems
with complex food webs capped by an
abundance of top-echelon predators into
simplified biotic communities increas-
ingly dominated by smaller animals, al-
gae, and microbes. Among the many
ramifications have been the economic
collapse of numerous marine fisheries
and massive degradation of coral reefs
that formerly rivaled tropical rainforests
in terms of spatial coverage and biotic
richness. The data paint a disturbing
picture about current and projected eco-
logical states for the world?s oceans.
David Wake and Vance Vredenburg
(7) describe a similarly gloomy scenario
for the global status of amphibians. Of
This paper serves as an introduction to this PNAS supple-
ment, which resulted from the Arthur M. Sackler Collo-
quium of the National Academy of Sciences, ??In the Light of
Evolution II: Biodiversity and Extinction,?? held December
6?8, 2007, at the Arnold and Mabel Beckman Center of the
National Academies of Sciences and Engineering in Irvine,
CA. It is the second in a series of colloquia under the general
title ??In the Light of Evolution?? (see Box 1). The complete
program and audio files of most presentations are avail-
able on the NAS web site at www.nasonline.org/
Sackler
biodiversity. Papers from the first colloquium in the
series, titled ??In the Light of Evolution I: Adaptation and
Complex Design,?? appeared in ref. 1.
Author contributions: J.C.A., S.P.H., and F.J.A. wrote the
paper.
The authors declare no conflict of interest.
?To whom correspondence may be addressed. E-mail:
javise@uci.edu or fjayala@uci.edu.
? 2008 by The National Academy of Sciences of the USA
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the 
6,300 extant species of frogs,
salamanders, and caecilians, at least
one-third are currently threatened with
extinction, and many more are likely to
become so in the near future. A dra-
matic worldwide decline in amphibian
populations was first noticed in the late
1980s. Several ecological factors includ-
ing habitat degradation and climatic
changes probably are involved, but so
too is an unanticipated, recently uncov-
ered threat: an emerging virulent dis-
ease (chytridiomycosis) caused by a
pathogenic fungus. The source of this
fungus and its mode of spread are
poorly understood, but the disease (per-
haps in synergy with other ecological
factors) has devastated amphibian popu-
lations in such distant sites as the Amer-
icas and tropical Australia. Whatever
the proximate and ultimate causes of
the ongoing amphibian extinctions, the
trend is especially disturbing because
amphibians otherwise have been quint-
essential evolutionary survivors that
managed to persist across several earlier
mass extinction events in the Earth?s
history.
Biodiverse coral reefs are among the
most threatened ecological systems on
Earth. Approximately 70% of coral
reefs globally have been degraded be-
yond recognition in recent years (20%),
are in imminent danger of collapse
(24%), or are under longer-term threat
of demise (26%) (8). Marjorie Reaka et
al. (9) survey reef-dwelling stomatopods
(a large group of marine crustaceans) as
a model taxon to assess global hotspots
of extant biodiversity, endemism, and
extinction risk, the intent being to iden-
tify evolutionary sources and sinks of
stomatopod diversity, infer driving
mechanisms, and provide an additional
focus for conservation and management
efforts on coral reefs. Stomatopod spe-
cies diversity (like that of several other
reef-dwelling marine taxa) is highest in
the Indo-Australian Archipelago, gradu-
ally declines eastward across the central
Pacific, and shows a secondary peak of
species richness in the southwestern In-
dian Ocean. From these and other data
(related to body size, ecology, and spa-
tial pattern of endemism), the authors
explain how a ??merry-go-round?? evolu-
tionary model might account for the
differential dynamics of species origin
and extinction in different ocean regions.
Extinctions in the ongoing biodiversity
crisis apply not only to free-living organ-
isms but also to their parasites. Andy
Dobson et al. (10) address the possible
magnitude of this problem by reviewing
estimates of the total number of para-
sitic species on Earth (with special
reference to helminthes that parasitize
vertebrate animals) and the fraction of
extant biodiversity that is parasitic. The
authors conclude that 
10?15% of par-
asitic helminthes (Trematoda, Cestoda,
Acanthocephala, and Nematoda) are at
risk of extinction by virtue of being de-
pendent on threatened or endangered
species of vertebrate host. They also
conclude that parasite species diversity
does not map linearly onto host species
diversity and that approximately three-
quarters of all links in food webs involve
a parasitic species. These findings pro-
vide a sobering reminder that the cur-
rent extinction pulse is affecting many
kinds of organisms (not just the conspic-
uous megafauna) and that extinction
processes could therefore have many
unforeseen ramifications for ecosystem
operations.
Contemporary Patterns and Processes in
Plants and Microbes
The anthropogenic introduction of alien
species is perhaps second only to habitat
loss as a cause of recent and ongoing
species extinctions. The problem is espe-
cially acute on oceanic islands, where
countless native animals have gone ex-
tinct after the arrival of humans and
their hitchhiking associates. Dov Sax
and Steven Gaines (11) examine histori-
cal records from islands around the
world to ask whether native plant spe-
cies likewise often have gone extinct
when exotic plants were introduced and
became naturalized. The answer seems
to be a clear no, at least yet. One possi-
bility is that native plant species on is-
lands are accumulating an extinction
debt that will be paid in future species
losses; alternatively, the number of na-
tive plus exotic plants on islands may
reach a stable equilibrium or saturation
point that is much higher than the en-
demics alone had been able to achieve.
The authors examine the evidence per-
taining to these competing hypotheses
and explore the ramifications for future
plant biodiversity on islands depending
on which scenario proves to be more
nearly correct.
The task of tallying extant species and
estimating extinction risks can be daunt-
ing even for relatively well studied bio-
tas. Such scientific exercises can also be
highly informative, as Stephen Hubbell
et al. (12) illustrate by applying neutral
biodiversity theory (13) to estimate the
number, abundance, range size, and ex-
tinction risk (under alternative scenarios
Box 1. In the Light of Evolution. In 1973,
Theodosius Dobzhansky penned a
short commentary titled ??Nothing in
biology makes sense except in the light
of evolution?? (25). Most scientists
agree that evolution provides the uni-
fying framework for interpreting bio-
logical phenomena that otherwise can
often seem unrelated and perhaps un-
intelligible. Given the central position
of evolutionary thought in biology, it is
sadly ironic that evolutionary perspec-
tives outside the sciences have often
been neglected, misunderstood, or pur-
posefully misrepresented. Biodiver-
sity?the genetic variety of life?is an
exuberant product of the evolutionary
past, a vast human-supportive resource
(aesthetic, intellectual, and material)
of the present, and a rich legacy to
cherish and preserve for the future.
Two challenges, as well as opportuni-
ties, for 21st-century science are to gain
deeper insights into the evolutionary
processes that foster biotic diversity
and to translate that understanding
into workable solutions for the regional
and global crises that biodiversity cur-
rently faces. A grasp of evolutionary
principles and processes is important in
other societal arenas as well, such as
education, medicine, sociology, and
other applied fields including agricul-
ture, pharmacology, and biotechnol-
ogy. The ramifications of evolutionary
thought extend into learned realms tra-
ditionally reserved for philosophy and
religion. The central goal of the In the
Light of Evolution series will be to
promote the evolutionary sciences
through state-of-the-art colloquia and
their published proceedings. Each in-
stallment will explore evolutionary
perspectives on a particular biological
topic that is scientifically intriguing but
also has special relevance to contem-
porary societal issues or challenges.
Individually and collectively, the In the
Light of Evolution series will aim to
interpret phenomena in various areas
of biology through the lens of evolu-
tion, address some of the most intel-
lectually engaging as well as pragmat-
ically important societal issues of our
times, and foster a greater appreciation
of evolutionary biology as a consoli-
dating foundation for the life sciences.
The organizers and founding editors
of this effort (J.C.A. and F.J.A.) are the
academic grandson and son, respectively,
of Theodosius Dobzhansky, to whose
fond memory this In the Light of Evolu-
tion series is dedicated. May Dobzhan-
sky?s words and insights continue to in-
spire rational scientific inquiry into
nature?s marvelous operations.
11454  www.pnas.org
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of future habitat loss) for medium- and
large-sized trees in the Amazon Basin.
Their quantitative analysis suggests that
11,000 tree species inhabit this ex-
traordinarily biodiverse region. The
good news for biodiversity conservation
is that 3,000 of these species have
large population sizes and therefore are
likely to persist well into the future
(barring catastrophic climatic or other
environmental changes). The bad news
is that for the large class of rare Amazo-
nian trees (5,000 species likely to con-
sist of 10,000 individuals each) esti-
mated near-term extinction rates are
37% and 50%, respectively, under opti-
mistic and nonoptimistic projections
concerning ongoing deforestation prac-
tices by humans.
With regard to tallying numbers of taxa
and characterizing local, regional, or
global patterns of biodiversity, microbes
offer even stiffer challenges than many
plant and animal taxa. Jessica Bryant and
colleagues associated with Jessica Green
(14) tackle such problems on a mesogeo-
graphic scale by applying DNA sequence
data (from the 16S ribosomal gene) and
other information to questions about mi-
crobial biodiversity along an elevational
habitat gradient in the Colorado Rocky
Mountains. Bacterial taxon richness along
their climatic-zone transect decreases
monotonically from lower to higher alti-
tudes, and detectable phylogenetic struc-
ture (nonrandom spatial clustering of
related taxa) occurs at all elevations. In
comparable analyses of plants along the
same gradient, the authors uncovered
qualitatively different outcomes with re-
gard to both taxon richness and species
assemblage. These findings indicate that
whatever ecological and evolutionary
forces shape microbial communities, the
biodiversity patterns will not always mirror
those in macrobiota.
An important follow-up issue for mi-
crobial (or other) taxa is whether the
composition of natural communities pre-
dictably influences the responses of
those communities to environmental
alteration. Traditionally, microbial com-
munities often have been treated as
??black boxes?? in functional ecological
models, a situation that Steve Allison
and Jennifer Martiny (15) would like to
see rectified. These authors review ex-
periments and observations from the
scientific literature to address questions
about the composition of a microbial
community after exposure to environ-
mental perturbations. Is the microbial
community resistant to the disturbance
(tend not to change in taxonomic com-
position)? Is it resilient (change in
makeup but then return quickly to the
predisturbance condition)? If an altered
composition is sustained, is the new
community functionally redundant to
the original? Based on the authors? liter-
ature review, the answers to these ques-
tions usually seem to be ??no,?? ??no,?? and
??no.?? Allison and Martiny emphasize that
all such conclusions remain provisional
pending further research of this nature,
and they suggest several promising empiri-
cal and conceptual approaches.
Trends and Processes in the
Paleontological Past
Extinction has always been a part of life
on Earth and is the ultimate fate of all
species. Rates of extinction have varied
across time, from standard or ??back-
ground?? rates to occasional mass events.
The articles in this section place the cur-
rent biodiversity crisis in temporal per-
spective by scrutinizing the fossil record
for patterns and processes of extinction
in the distant and near past.
The fossil record traditionally has been
interpreted to register five episodes of
wholesale biotic change so severe as to
qualify as mass extinctions: at the end of
the Ordovician (
440 mya), Devonian
(370 mya), Permian (245 mya), Triassic
(210 mya), and Cretaceous (65 mya).
Each was characterized (indeed identified)
by a substantial loss of then-extant taxa.
Douglas Erwin (16) reexamines these five
mass extinction events in terms of the re-
spective impacts on each of seven metrics
of biodiversity?taxonomic diversity, phy-
logenetic diversity, morphologic disparity,
functional diversity, architectural diversity,
behavioral complexity, and developmental
diversity?which potentially capture differ-
ent aspects of the loss of evolutionary his-
tory. Erwin reports that the canonical
mass extinctions differed with respect to
their impacts on these various metrics. For
example, the end-Permian extinction had
major consequences for essentially all di-
mensions of global biodiversity whereas
the end-Ordovician extinction heavily im-
pacted morphologic disparity but had low
or medium effects on several other biodi-
versity measures. The biodiversity fallout
from mass extinction events can vary both
quantitatively and qualitatively, and the
nature of each extinction influences the
rate and pattern of evolutionary recovery
from the catastrophe.
David Jablonski (17) develops a
somewhat similar theme by emphasizing
the selectivity of mass extinctions with
respect to potential risk factors such as
body size, species richness, and geo-
graphic range. From a consideration of
the fossil record for marine organisms
(especially bivalve mollusks), the author
concludes that every mass extinction
event seems to show some degree of
selectivity, but also that disproportion-
ately high clade survivorship during
mass extinction episodes is consistently
associated with the size of the geo-
graphic range of genus-level clades.
From this and other evidence, the au-
thor?s take-home message is that spatial
considerations are fundamental to un-
derstanding the evolutionary dynamics
of biodiversity, including a clade?s sus-
ceptibility to extinction and its potential
for recovery and expansion after a mass
extinction event. These findings have
ramifications for the current biodiversity
crisis because human activities are alter-
ing the geographic distributions of many
taxa around the world.
John Alroy (18) uses information
from a recent web-based ??Paleobiology
Database?? to revisit classical questions
about the marine fossil record, such as:
Do biotic turnovers occur in pulses that
coincide with the boundaries between
geological intervals? Did extinction rates
decline during the Phanerozoic? Are
biotic extinction rates more volatile than
origination rates? Do large-scale extinc-
tions exhibit a 26-myr periodicity as
some have claimed? Were the ??Big
Five?? mass extinction events qualita-
tively distinct from lesser extinction epi-
sodes? Alroy?s provisional answers to
some of these questions are unorthodox.
For example, he suggests that the Big
Five are merely the upper end of a con-
tinuous spectrum of extinction intensi-
ties, such that it is ??a matter of taste
whether to speak of the Big Five, the
Big Three, or just the Big One. . . ??. The
analyses yield empirical estimates of typi-
cal recovery times from mass extinctions.
Alroy concludes that the rebound from
the ongoing mass extinction will probably
take between 15 and 30 million years, if
past mass extinction events are any guide.
Moving closer to the present time,
late-Quaternary extinctions heavily im-
pacted large mammals especially. The
last 50,000 years were witness to the ex-
tinction of approximately two-thirds of
all genera and one-half of all species of
mammal weighing 44 kg (about the
size of a sheep). Causal factors for this
megafaunal extinction have been much
debated, with a leading hypothesis being
human hunting (overkill) arguably aug-
mented by habitat alteration and climate
change. Anthony Barnosky (19) exam-
ines the situation from the fresh per-
spective of historical tradeoffs in bio-
mass. An inverse relationship between
human biomass and nonhuman
megafaunal biomass indicates that be-
fore the mass extinction the energy
needed to construct large animals was
divided among many species, whereas
after the extinction much more of the
planet?s total supply of energy became
concentrated in one species (Homo sapi-
ens) and its domesticates. Based on the
historical chronologies of biomass transi-
Avise et al. PNAS  August 12, 2008  vol. 105  suppl. 1  11455
tions in various parts of the world, Bar-
nosky draws several biological implica-
tions, including how the current
depletion of fossil fuels as an energy
source may translate into near-future
challenges for global biodiversity.
Prospects for the Future
Armed with evidence from the past and
present about global patterns and pro-
cesses of extinction, what can be pro-
jected for global biodiversity in the near
and distant future? Articles in this section
address several of the many challenges
presented by the ongoing extinction cri-
sis, both for the biodiversity sciences per
se and for efforts to translate the science
into an enhanced societal awareness that
might spawn effective conservation poli-
cies and actions.
Conventional wisdom has been that
ecologically important traits (such as an
ability to withstand cold climates) are
too evolutionarily labile to be of much
utility in phylogenetic inference. Michael
Donoghue (20) challenges this paradigm
by reviewing several cases in which
higher plant taxa have retained, for long
periods of evolutionary time, particular
traits that impact their geographic distri-
butions. Donoghue calls this phenome-
non ??phylogenetic niche conservatism.??
His basic idea is that the geography of
biodiversity at any horizon in time re-
flects an interaction between phyloge-
netic legacy (as registered in the evolved
ecological characteristics of particular
lineages) and contemporary ecological
selection pressures. This worldview im-
plies that evolutionary shifts from one
ecological setting to another cannot be
readily accomplished by many plant
taxa, especially if substantial genetic ad-
justments in physiology are required.
Thus, newly opened niches are more likely
to be filled by immigrants from ecologi-
cally similar zones than by in situ evolu-
tion of local populations. Donoghue
addresses some ramifications of phyloge-
netic niche conservatism for the future of
plant biodiversity in the face of global cli-
mate change and habitat fragmentation.
In a somewhat similar vein, Jonathan
Davies and colleagues associated with
the Andy Purvis group (21) show how a
phylogenetic modeling approach can
help to identify mammalian taxa whose
intrinsic biology might make them espe-
cially vulnerable to environmental
pressures. They begin by combining phy-
logenetic information from a recently
completed Tree of Life for mammals
with ecological, life history, and geo-
graphic data to examine the origins and
current distributions of mammalian
biodiversity. Results from the analysis
indicate that evolutionary cradles of ori-
gin have shifted over time and that ex-
tinction risks vary according to the type
of mammal (e.g., large-bodied versus
small-bodied) and also to spatial and tem-
poral differences (often region-specific) in
threat intensity. The authors discuss rami-
fications of such phylogenetic findings for
the near- and long-term future of mam-
malian biodiversity, including how alter-
native criteria (different ??currencies of
conservation??) might be used in setting
preservation priorities.
Before the mid-20th century, scientific
analyses of biodiversity rested on ap-
praisals of organismal phenotypes. That
situation changed dramatically when
molecular techniques were introduced
that permitted direct assays of geno-
types. The molecular revolution in evo-
lutionary biology has provided powerful
tools for biodiversity assessments ranging
from species identifications and phylog-
eny reconstructions to genetic dissec-
tions of ontogeny. Projecting forward,
John Avise (22) describes three oppor-
tunities for the field of biodiversity ge-
netics that seem not to have been widely
appreciated or discussed: use informa-
tion from the emerging phylogenetic
Tree of Life to erect the first-ever uni-
versally standardized scheme of biologi-
cal classification; identify biogeographic
hotspots and centers of origin (including
those tracing to the late-Tertiary) for
various extant biotas; and engage in ed-
ucational outreach by conveying to stu-
dents and the public a sense of wonder
and appreciation for the marvelous work-
ings of nature, many of which are being
revealed for the first time by genetic ap-
praisals. Capitalizing on these opportuni-
ties should be instructive for basic science
and also helpful in conservation efforts.
Michael Novacek (23) expands on the
public-outreach mission for conservation
biology by emphasizing the need to
awaken a broad audience to the ongoing
biodiversity crisis. Despite the urgency
of current environmental problems, and
committed efforts (albeit by relatively
small segments of society) over the past
20 years to find solutions, national and
international responses to date have
been slow to materialize and inadequate
to steward global biodiversity through
the crucial 21st century. One major rea-
son is the general lack of understanding
and engagement on biodiversity issues
by the public, which in polls typically
ranks environmental concerns below
other challenges such as terrorism, the
economy, and family values. Novacek
analyzes this state of affairs and argues
that effective ways must be found to tailor
biodiversity messages to each target au-
dience. Enlightened environmental mea-
sures by corporations and democratic
governments will be achieved only if the
??power of the people?? is marshaled in
favor of conservation efforts.
In the closing article of this Collo-
quium, Paul Ehrlich and Robert Pringle
(24) remind us that ??the fate of biologi-
cal diversity for the next ten million
years will be determined during the next
50?100 years by the activities of a single
species?? (Homo sapiens). With the pro-
jected increase by mid-century of 2.6
billion people to an already over-
crowded planet, the prospects for pre-
serving substantial biodiversity are dim,
unless societal mindsets and comport-
ments change dramatically and quickly.
The authors issue a pluralistic call for
action on seven fronts: combat the
underlying drivers of biodiversity loss
(notably human population growth,
overconsumption, and the use of malign
technologies); promote permanent na-
ture reserves; provide social and eco-
nomic incentives to preserve wild
populations; better align economies
with conservation; restore biodiversity
on currently degraded lands; vest human
occupants of a region with the desire
and capacity to protect nature; and, in
general, fundamentally transform human
attitudes toward nature and biodiversity.
These calls are ambitious, but positive
societal responses to them are not yet
beyond the realm of possibility.
The current extinction crisis is of hu-
man making, and any favorable resolu-
tion of that biodiversity crisis?among
the most dire in the 4-billion-year his-
tory of the Earth?will have to be initi-
ated by mankind. Preserving biodiversity
is undeniably in humanity?s enlightened
self-interest, but the tragic irony is that
a majority of humanity is not yet en-
lightened to this fact. Little time re-
mains for the public, corporations, and
governments to awaken to the magni-
tude of what is at stake.
1. Avise JC, Ayala FJ, eds (2007) In the Light of Evolution I:
Adaptation and Complex Design. Proc Natl Acad Sci
USA 104(Suppl):8563?8676.
2. Kellert SR (2005) Perspectives on an ethic toward the
sea. Benthic Habitats and the Effects of Fishing, eds
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