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Chapter 2
Species Extinctions
EXTINCTIONS OVER GEOLOGICAL TIME
Any attempt to reduce human-caused species extinction (i.e., to protect endangered species)
requires an understanding of extinction rates over geological time. Fossil records from nearly any
geological age reveal two types of extinction: extinction without replacement ("dead-end") and what
might be called "chronologic extinction" or "taxonomic extinction." The first type is genuine
extinction; it is the end of an evolutionary lineage. The second type is based on the recognition by
paleontologists that one species has changed through geological time (i.e., has evolved) to the extent
that it is classified as a different species from the next earliest representative of its lineage. The species
involved (see Martin and Barnosky, 1993; Nadachowski, 1993; Turner, 1993) represent an
evolutionary continuum rather than an evolutionary dead-end. The discussion that follows is concerned
only with dead-end extinction.
The past 20 years have witnessed major advances in our understanding of the earth's physical
history (including understanding of paleoclimate, changing sea level, volcanism, and plate tectonics),
and knowledge of past plant and animal communities is much improved. With refinements in
radiometric dating, stratigraphy, and the discovery and analysis of varied sources of
paTeoenvironmental data (from cave deposits, ice cores, pollen cores, fossil dung, packrat middens, tree
rings, etc.), we now can correlate many biotic and abiotic events in earth history with reasonable
accuracy. What we learn from studying the past is important for predicting biotic responses to future
changes in climate and other physical phenomena (Burney, 19931.
The marine invertebrate fossil record reveals at least five mass-extinction events during the past
500 million years, in which from 14% to 84% of the genera or families disappeared from the fossil
record (lablonski, 1991; Raup and Jablonski, 1993; Benton, 1995~. Perhaps the two best known of
these mass-extinction events are the Permian-Triassic (P-T) 245 million years ago and the Cretaceous-
Tertiary (K-T) 65 million years ago. In addition to marine invertebrates, the P-T event involved
extinction of terrestrial plants and insects (Retallack, 19951; the K-T event included most reptiles. A
much more recent mass extinction, that of the Pleistocene-Holocene (P-H) only 1 i,000 years ago,
featured extinction of more than 100 terrestrial species of birds and large mammals in North, Central,
and South America. Although extinction is common to the P-T, K-T, and P-H events, they differ from
the current extinction event in several ways.
The current extinction event differs from the three paleontological events in that it actually or
potentially involves all groups of organisms, in any sort of nonmarine habitat. A particularly
conspicuous aspect of today's situation is that many species of plants, as well as animals, are rare,
endangered, or already have become extinct. For example, the Endangered Species List contained 695
U.S. and 521 non-U.S. endangered species and 169 U.S. and 41 non-U.S. threatened species in
March, 1995. Of that total, 995 were animals and 529 were plants.
In two of the other three extinction events, plants suffered few if any losses. The evolutionary
radiation of mammals that followed the K-T demise of most reptiles was possible only because most
terrestrial plants survived the K-T event. As far as can be determined from the extensive late
Quaternary pollen and plant macrofossil record, the loss of so many birds and mammals in the
19
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Science and the Endangered Species Act
Americas during the P-H event was not accompanied by the extinction of plants, although the
geographic ranges of plants changed dramatically at that time (Betancourt et al., 1990; Webb et al.
1993).
Today, even though obscure or littIe-known species are lost with little or no notice (Wilson,
1992), we can document the date of loss of relatively well-known species to the nearest decade (e.g.,
the sea mink, Mustela macrodon, became extinct about 1880 (Nowak and Paradiso, 1983), sometimes
to the year (e.g., the Guam flycatcher, Myiagra freycineti, became extinct in 1985 (Engbring and Pratt,
1985; Steadman, 1992), or even to the clay, in the case of the last passenger pigeon, Ectopistes
migratorius, which died on September i, 1914 (Schorger, 1955~. Such precise dating is not possible
for the paleontological extinctions. Because they occurred within the time range of radiocarbon dating,
the 95 % confidence limits to the estimated dates of P-H extinctions are + 50 to 200 years (Stafford et
al., 1990~. But for the K-T and P-T events, even the most precise radiometric dating methods have
margins of error (a 95 % confidence interval) of + 104 to 1Os years and lOs to lo6 years, respectively.
Pinpointing prehistoric extinctions also depends upon the completeness of the fossil record, because
failure to find a species in a certain fossil assemblage does not mean that the species is extinct; the
absence could be a sampling artifact (Steaciman et al., 1991~.
The P-T and K-T events are not as well documenter! as the P-H event because they are
represented by many fewer paleontological sites, and a much greater variety of organic materials have
withstood the mere ~ 1,000 years since the P-H event. Furthermore, most species that were lost in the
P-T and K-T events are related only distantly to living species; in contrast, many birds and mammals
lost in the P-H event are survived by closely related species or genera that can be studied to help
determine the paleoecology of the extinct species.
A series of glacial-interglacial cycles have occurred during the past 2 million years. The coo!
glacial intervals have lasted 80,000 to 120,000 years, ant! the warm interglacial intervals have lasted
only 10,000 to 20,000 years each. The temperature and atmospheric chemistry of our current
interglacial period (the Holocene) have been unusually stable (Ramnino and Self. 1992: Dans~aard et
-of or------ x~ , - ~ -a - --- - ~ --- ~ ___ _ ~ ~
al., 1993; Mayewski et al., 1993~; however, even subtle shifts in Holocene temperature or precipitation
regimes can have dramatic local consequences on plant communities (Swetnam, 1993~. The last
interglacial interval, which probably had much more variable temperatures than the current one, lasted
from about 130,000 to 115,000 years ago (Appenzeller, 1993; Dansgaard et al., 1993; GRIP, 1993;
Grootes et al., 1993; Martinson et al., 1987; Shackleton, 1987~. Global sea-level fluctuations between
glacial and interglacial intervals have been on the order of 100 m (Shackleton, 1987; Pirazzoli, 1993~.
Warm interglacial climates have characterized about 15 % of the past 2 million years (Imbrie
and Imbrie, 1979~. During glacial intervals, which featured continental ice sheets, expanding alpine
glaciers, and periodic "armadas" of icebergs across the North AtIantic (Kerr, 1993a), the average air,
soil, and groundwater temperatures were much cooler than today, even in subtropical Florida
(Plummer, 1993) and in truly tropical localities (Markgraf, 1989~. In those times, species could
survive the great continental climatic fluctuations because they could move gradually across intact
habitats. The response of plants and animals to climatic changes of the next glacial interval will likely
be impaired! by habitat fragmentation. Species with poor dispersal capabilities might be unable to shift
their ranges across tracts of ctisturbecI habitat.
PREHISTORIC HUI\lAN IMPACT ON CONTINENTAL ECOSYSTEMS
Although the causes of the P-T and K-T extinction events are topics of much interest, research,
and speculation (e.g., lablonski, 1991; Kerr, 1993b; Morell, 1993; Sharpton et al., 1993), we can be
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Species Extinctions: Extinctions Over Geological Time
21
certain that humans were not involved. That might not be the case, however, for the P-H event and
certainly is not so for the current extinction event. As far as can be determined, human activity has
significantly increased rates of extinction perhaps by orders of magnitude over the background rate
(see below) and therefore is the primary cause of the current extinction event (Wilson, 19921. How far
back in time can we trace human impact?
Humans, including early forms of Homo and modern Homo sapiens, have occupied much of
Africa and Eurasia for hundreds of millennia (Diamond, 1992; Klein, 19941. Archaeological evidence
(especially bone assemblages and stone tools) suggests that people in Africa and Eurasia have hunted
large mammals since at least 100,000 years ago (Nitecki and Nitecki, 1986~. This early human
predation probably focuses} on small or weak indivicluals rather than large, potentially dangerous
animals. A major advance occurred in hunting proficiency 40,000 years ago, perhaps coinciding with
the evolutionary emergence of modern people (Klein, 19841. For the first time, systematic and
organized predation on large, powerful animals became an important part of human subsistence. It is
likely that the first appreciable human effects on vertebrate faunas occurred at this time (Klein, 1992~.
Nevertheless, only seven species of large mammals (one elephant, one horse, one camel, one
diner, and three bovic3 species) clisappeared from Africa cluring the late Pleistocene (Martin, 19841.
This might be because African large mammals were hunted by humans while humans were evolving
anatomically and behaviorally. As a result, most African mammals, to varying extents, were able to
survive prehistoric human predation, because they had the opportunity to evolve in response to human
predation as the humans evolved.
In the Americas, the first human occupation was by modern Homo sapiens, who was able to
cross the Bering Strait land bridge because of lowered sea levels. The North American vertebrate
fossil record of the past 2 million years reveals little extinction without replacement until the first
humans arrived about 11,000 years ago (Martin, 19901. At that time, an overall warming trend was
also causing major changes in the latitudinal, elevational, ant! edaphic ranges for most species of plants
(Webb et al., 1993~. The P-H extinction event primarily affected large-mammal species (244 kg);
nearly all amphibian, reptile, and small-mammal species survived. A variety of North American
megafauna was lost, including two glyptodont, four ground sloth, two bear, two sabertooth, one
cheetah, one beaver, two capybara, two mastodon, one mammoth, one horse, one tapir, two peccary,
three camel, two deer, one pronghorn, and four bovid genera (Martin, 1984, 1990~.
The collapse of the large North American mammal communities led to the demise of dependent
species, such as carrion-feeding birds that fed on the abundant variety of carrion provided by herds of
large animals, much as in modern African game parks. For example, eleven thousand years ago, when
ground sloths, mammoths, mastodons, horses, tapir, camels, and other species existed across North
America, the currently endangered California condor lived as far away as Florida and New York
(Steadman and Miller, 19871.
People spread rapidly across the Bering Strait and North America, and within only hundreds of
years, descendants of these big-game hunters dispersed throughout Central and South America as well.
Their spears tipped with stylistically distinctive projectile points have been found with the bones of
extinct megafauna (especially mammoths) at sites radiocarbon-dated to within a century or two of
,000 years ago.
According to the "Pleistocene overkill theory," early big-game hunters were the primary or
only cause of the collapse of American large-mammal communities (Martin, 1984; 1990; Diamond,
1992~. Scientists opposed to the overkill theory generally believe that changing climates and habitats
were the sole or main cause of the P-H extinctions, but cannot explain why American large-mammal
communities that survived many glacial-interglacial cycles quickly collapsed at the same time human
populations in North America first became significant. Some scientists favor a combination of
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Science and the Endangered Species Act
cI~mate/habitat stress and human predation as the cause for the P-H extinctions (Owen-Smith, 1987~.
Regardless of the cause (Martin ant} Klein, 1984), the extinctions must have had a serious effect on
North American ecosystems that once included a variety of grazers and browsers, not to mention their
predators and commensals.
When climates warmest at the end of the last glaciation, plant communities of southern regions
or low elevations did not simply move as entire communities. Instead, species of plants responded
individually and, therefore, plant communities assembled cluring the Holocene were not the same as
those that had existed farther south or at lower elevations during the late Pleistocene (Betancourt et al.,
1990; Pielou, 1991~. The distributions of surviving species of mammals also changed, again somewhat
independently rather than as intact communities (Semken, 19831.
With most of the large mammals extinct, some peoples shifted to a more generalized diet, while
others specialized in hunting bison, which survived into the Holocene. Bones from North American
Holocene archaeological sites might represent as many as 50 species of vertebrates ranging from frogs
and songbirds to eagles, bear, deer, and moose. Many of these sites bear evidence of species well
outside their known post-Columbian range (Semken, 1983; Pielou, 1991~. Intertribal trading of bircis
and mammals might account for some of these distributions, although many, if not most, reflect
formerly indigenous populations, including species such as the trumpeter swan, Mississippi kite,
swallow-tailed kite, whooping crane, sanc~hill crane, long-billed curlew, Carolina parakeet, ivory-billed
woodpecker, common raven, fish crow, rice rat, Allegheny woodrat, fisher, and puma. Prehistoric
hunting, trapping, habitat modification, and climate-ciriven habitat changes might have been involved in
some of the contractions of species' ranges.
In parts of North America, the domesticatecl bottle gourd, chili pepper, beans, squash, and
maize existed 5,000-6,000 years ago. The more sedentary lifestyle that came with agriculture was
accompanied by a reduced dependence on wild plants and animals. But the gradual transition probably
entailed shifting cultivation rather than long-term use of the same plots, and hunting, trapping, fishing,
and gathering remained an important part of subsistence in most of North America long after plants and
animals were domesticated. At the time of European contact, North American Indians still hunted
turkey, black bear, deer, elk, moose, bison, and many smaller species. Some species, such as the
California condor (Simons, 1983; Bates et al., 1993) and eagles, were hunted for feathers, bones, or
ceremonial purposes rather than for food.
Agriculture affects ecosystems through the reduction or loss of certain species of plants and
animals, the propagation of others, and modifications of landscape, soils, and water supply through
deforestation, erosion, deposition, channeling, flooding, and draining (Steadman, in press). Use of
pesticides, energy supplements, and grazing are other factors. Because of the good water supply and
fertile alluvial soils, much early agriculture developed along major river valleys; consequently, riparian
biotas have been disturbed for centuries, if not millennia (Rea, 19831.
Chaco Canyon, New Mexico, is a clear example of prehistoric overexploitation of natural
resources, as revealed by studies of plant macrofossils from ancient packrat middens (Betancourt and
Van Devender, 1981; Betancourt et al., 19861. The buildings constructed at Chaco Canyon from about
AD 900 to ~150 by the Anasazi required 200,000 beams from large coniferous trees (ponderosa pine,
subalpine fir, and blue/Englemann spruce). The trees were brought from as far away as 75 km,
because these alpine conifers cannot live in the tow elevation of Chaco Canyon. When the Anasazi
arrived, the area around Chaco Canyon was a pinyonjuniper woodland. The pinyon and juniper trees
provided firewood for the Anasazi, who farmed a narrow band of floodplain soil near their dwellings.
As time progressed, the Anasazi had to go 15 km or more from Chaco Canyon just to gather
firewood. They had transformed the area from a pinyonjuniper woodiancl to a nearly woodIess desert
scrub. The removal of pinyon, juniper, and riparian trees produced soil erosion, increased runoff, and
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Species Extinctions: Extinctions Over Geological Time
23
probably a lowered water table in Chaco Canyon, all of which made it difficult to continue irrigated
farming of the valley bottom. Drought-stressed agriculture and lack of firewood might have caused the
Anasazi to abandon Chaco Canyon about 700 years ago (Betancourt and Van Devender, 19811.
Scattered junipers grow at Chaco Canyon today, but no pinyons do. The incised streambed would be
virtually impossible to modify today for agriculture. Because of human activities that began more than
1,000 years ago, Chaco Canyon still sustains impoverished plant and animal communities and remains
a poor place for people to live.
Another example of prehistoric humans having a significant effect on the carrying capacity of
their ecosystems involves the Aleuts, whose overexploitation of sea otters appears to have changed the
coastal ecosystems of the Aleutian Islands as long as 2,500 years ago (Simenstad et al., 1978~.
PREHISTORIC HUMAN IMPACT ON ISLAND ECOSYSTEMS
The relatively small land areas of islands result in small populations of organisms that tend to
be more vulnerable to extinction than those on continents (MacArthur and Wilson, 19671. Compared
with continental species, a much greater proportion of island species have become extinct or
endangered during the past several centuries of exploration and exploitation. In the past 2 decades, we
have learned that, at least for vertebrates, human-caused extinctions had occurred on the world's
islands during prehistoric times. Those extinctions seem to have been due to the same processes that
lead to the extinction of island species today: direct human predation, predation from introduced
mammals (such as rats, dogs, and pigs), habitat changes (such as those caused by deforestation,
agriculture, and introduction of exotic plants), and introduced pathogens (such as avian malaria and
avian pox).
One way to assess the environmental impacts of prehistoric peoples on oceanic islands is to
study the biotic history of islands that never were inhabited in pre-Columbian times. According to
biogeographic theory, background extinctions are a regular part of an island's biological heritage.
Knowing the rate of background extinction allows the severity of the human-caused extinction we see
today to be evaluated. The human history of the Galapagos Islands, for example, began with brief
Spanish and British visits in the 16th and 17th centuries. We can examine the pre-Columbian
Galapagos biota to determine the level of background extinction.
Thirty-four species of reptiles, birds, and mammals are known to have become extirpated in the
Galapagos during the Holocene (Steadman et al., 19911. The Holocene vertebrate fossil record from
the Galapagos is based upon 15 sites from five different islands, with nearly 500,000 identified bones
spanning the past 8,000 years. This record reveals only three extinct populations or species that might
have become extinct before human contact. In other words, 31 of the 34 known extinctions occurred
after the arrival of people 200 years ago. A similar pattern has been corroborated in Tonga, where the
arrival of humans 3,000 years ago caused more extinctions of birds than had occurred during the
previous 100,000 years (Steadman, 19931.
Approximately 9,600 species of birds exist today (Sibley and Monroe, 1990~. The prehistoric
human colonization of Pacific islands (Melanesia, Micronesia, and Polynesia) resulted in the loss of as
many as 2,000 species of birds, especially flightless rails, but also petrels, ibises, herons, ducks and
geese, hawks and eagles, megapodes, sandpipers, gulls, pigeons and doves, parrots, owls, and
passerines (Steadman, 1989; 1991; 1993; 19951. The world avifauna would be about 20% richer today
had islands of the Pacific remained unoccupied by humans.
In the Hawaiian Islands, at least 77 endemic species of birds have become extinct since the
arrival of Polynesians nearly 2,000 years ago (Iames and Olson, 1991; Olson and lames, 1991) (see
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Science and the Endangered Species Act
Table 2-~. Furthermore, several incliviclual island populations of species have been reduced or
extirpated. Most extinct species of Hawaiian birds, including the majority of cardueline finches (the
"Hawaiian honeycreepers"), died out before the arrival of Europeans (Olson ant! lames, 1982; 1984;
lames et al., 19871.
On huncirecis of tropical islands, including those that are a part of or affiliated with the United
States (Puerto Rico, U.S. Virgin Islancls, Hawaii, American Samoa, and various Micronesian island
groups), the prehistoric and ongoing extinction of numerous populations and species of birds has
consequences beyond losing the birds themselves. Most of the extinct land birds were omnivores,
frugivores, granivores, or nectarivores; indigenous plants might have depended on those birds for
pollination or seed dispersal. Many species of Pacific island trees and shrubs seem to have no natural
means of intra- or interisland dispersal today. Because island! biotas are so degraded (i.e., so many
populations and species already are extinct), enciangered-species programs on islands face an
extraordinary challenge to maintain conditions that might permit the long-term survival of the
.
remaining species.
RELATING THE PAST TO THE PRESENT
Ecosystem Degradation and Restoration
Environmental problems often are viewed as modern phenomena. It is true that most plant and
animal communities have been affected by the past 2 centuries of commercial and residential
development; nonetheless, most of the earth was far from pristine in preindustrial times. The use of
tools and fire has set humans apart from other animals for many millennia, and all ancient human
societies had various effects on the ecosystems within which they lived (e.g., Simenstad et al., 1978;
Betancourt and Van Devencler, 1981; Betancourt et al., 1986; Diamond, 1992~.
TABLE 2-l Loss of Birds in the Hawaiian Islancis Since Human
Arrival*
Number of Number of Extirpated
Species Extinct Species Populations
-
Petrels 1 2
Ibises 2 3
Waterfowl 9 17
Rails 12 14
Hawks 2 6
Owls 4 4
Crows 2 5
Warblers 0 1
Thrushes
1
Honeyeaters 6
Drepani(line finches 38
4
9
56
Total 77 121
.
*Data condensed from James and Olson (1991) and Olson and James (1991).
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Species Extinctions: Extinctions Over Geological Time
By studying the effects prehistoric peoples had on the environment, we can begin to estimate
the composition of plant and animal corrununities cluring two critical times: before human contact
(when communities were pristine) ant} at western contact (when all previous human effects hac! been
due to native peoples). Such knowleclge is important for {ong-term projections of community stability,
as well as to help understand to what extent various communities might recover from human
disturbances.
This is not to suggest that the environmental conditions that prevailed in 1492, when major
European exploration of the Americas began, be the benchmark for discussion of the condition of any
given ecosystem or a goal for restoration. First, North America was not pristine then. The last time
our continent was unaffected by human activity was late in the last glacial interval, when a dramatically
different climate resulted in plant ant! animal associations that simply would not be possible in today's
climate. In addition, exact reconstructions of 1492 biotic communities would be impossible because so
many species, subspecies, anti varieties of plants and animals already have been lost. The grizzly bear,
gray wolf, and mountain lion, for example, no longer occupy more than a million km2 of their former
North American ranges (Mech, 1974; Currier 1983; Pasitschniak-Arts, 19931. Given current habitat
conditions and land-use patterns, restoration of these species would be impractical in much of their
25
former ranges.
__ . -by · ~ , - 1 , ,1 _1_ · ~ 1_~_ ~ ~ C_1 ~ ~1_ ~ A_ ~
However, we Still can use 1nrormal1on anoul me prenlslorlc envlronmcllr aara w Blip plan 1or
the future. Many tracts of land in North America are relatively undisturbed, and if biologically
feasible, we might try to restore locally extirpated species as part of a recovery program for
endangered species. Rather than using past distributions as strict guiclelines for restoration efforts, the
data could be part of planning conservation programs, with a goal of preserving plant and animal
communities that approach those of a less disturbed state. In some cases, such as on Pacific islands,
prehistoric information provides clear direction for transiocating endangered species onto islands that
once were part of their natural range (Franklin and Steadman, 1991~.
Rates of Extinction
In a 1992 report to Congress, the U.S. Fish and Wildlife Service categorized 711 species of
plants and animals as follows: improving 69 (10%), stable 201 (28%), declining 232 (33%),
extinct 14 (2%), and unknown 195 (27%) (USFWS, 19921. The relative proportions of these
categories among plants and animals are similar, except for extinctions, all of which are animals. The
232 declining species eventually will become extinct unless the decline is halted.
Rates of extinction are difficult to quantify precisely, in part because various authors measure
them in different ways (Benson, 1995~. However, examinations of relative rates of extinctions and of
well-known biota make it clear that extinctions are increasing in many groups of organisms (Nott et al.
1995).
For example, Nott et al. provided estimates of regional and global extinction rates based on
some well-known examples. They listed 36 species that had become extinct in the last 100 years of the
8,500 species in the South African floristic community known as pinkos; another 618 were deemed to
be at some risk of extinction. Forty taxa mostly species- of the approximately 950 species of
freshwater fishes in the United States became extinct in the past 100 years, with more than 100 at risk
of extinction. Of the 297 North American species and 13 subspecies of freshwater mussels in North
America, 21 have become extinct since the beginning of this century and 120 are endangered. Sixty
species of mammals have become extinct in the recent past; of those, 18 were found among the 300
species in the nonmarine Australian mammal fauna. An additional 43 species have been lost from more
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Science and the Endangered Species Act
than 50% of their former ranges. (Other well-known cases, such as bircis and plants on islands and the
cichlid fishes of Lake Victoria are discussed elsewhere in this chapter.)
Nott et al. (1995) made a conservative estimate of global extinction rates for various taxonomic
groups by assuming that no other species in those groups hac! become extinct worldwide and then
dividing the number of regional extinctions by the global number of species in the groups. The
resulting estimated global extinction rates which wouici have been larger if other known extinctions
were included in the estimate ranged from 10 to 1,000 times the estimates! background rates. They
predicted that future extinction rates, based on knowledge of species currently at risk of extinction,
would be even higher.
Part of the difficulty in grasping the significance of extinction rates is that they should be
evaluatecl in intervals of millennia or more, as well as the seasons, years, or decades that measure most
ecological studies. Another well-studiec! taxonomic group is North American bircis. At least 20 to 40
species of birds were lost at the end of the Pleistocene, mainly because of the extinction of large
mammals on which they ciepenclecl (Steaclman and Martin, 1984; Steadman and Miller, 1987; Emslie
1987, 19901. In the next 10,000 years, before the arrival of Europeans, only two North American
species definitely became extinct, the flightless marine cluck Chendytes lawi (Morejohn, 1976; Guthrie
1992) and the small turkey Meleagris crassipes (Rea, 19801.
In the past 200 years, at {east five species of birds have been lost (great auk, Labrador duck,
passenger pigeon, Carolina parakeet, and ivory-billecl woodpeckers. Two others, the Eskimo curlew
and Bachman's warbler, are near extinction. Several other species persist today in small, local
populations (e.g., California condor, whooping crane, red-cockaded woodpecker, black-capped vireo,
golden-checked warbler, and KirtIand's warbler). Some of those last eight species are likely to die out
in the next 200 years, as are others that are known to be endangered, threatened, or in decline today
(see North American Breeding Birc} Survey data for examples of birds whose populations have declined
substantially in recent years).
Most climatologists believe that the world will experience another ice age "unless there is some
fundamental and unforeseen change in the climate system" (Imbrie and Imbrie, 1979~. Indeed, the
earth's climate has varied as far back as we can tell anything about it and almost surely will continue to
vary. If the extinction rate of birds continues to be about five species per 200 years or about 25 species
per millennium, there could be hundreds fewer species to face the changing habitats that will come with
North America's next ice age or any major climatic change. Speciation (i.e., the evolution of new
species) is unlikely to offset these losses. The extinction of birds could affect other organisms as well.
For example, many species of North American plants may face a northward range shift if the climate
warms (or a southward shift if it cools); they will have to accomplish this task without the passenger
pigeon, which was by far the most abundant consumer and disperser of their seeds until a century ago.
Habitat Loss
Species endangerment and extinction have three major anthropogenic causes overhunting or
overharvesting; introduction of nonnative species, including the spread of disease; and habitat
degradation or loss. All three causes probably were factors in prehistoric as well as moclern times. In
some locations and for certain species, the first two have been the most critical. For example, the
decline of some species of marine vertebrates, such as certain whales, can be attributed largely to
commercial overexploitation. And many bircis in the Hawaiian Islands have suffered from predation
and diseases caused by introcluced species (Olson and James, 1982; Ehrlich et al., 1992~.
For most species in decline ant! for most of those on the edge of extinction in the U.S. today,
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Species Extinctions: Extinctions Over Geological Time
however, the most serious threat appears to be habitat degradation or loss (hereafter denoted as habitat
destruction). Habitat destruction is the primary threat to the majority of endangered and threatened
plants (Cook and Dixon, 1989) and is an increasing threat to songbirds and freshwater fishes (Miller et
al., 1989; Ehrlich et al., 1992; Allen and FIecker, 1993; Noss et al., 1995) and perhaps for hundreds
or even thousands of the lesser-known invertebrates in the United States (Deyrup and Franz, 19941.
Habitat destruction is described either as the current rate of destruction (expressed in
hectares/year) or as a cumulative amount of destruction (expressed as a percentage of some historic
baseline). No comprehensive summary has been compiled of the current rates of destruction of major
habitat types, but several studies have reviewed cumulative losses in particular regions, such as
California (Jensen et al., 1993), and for particular habitat types such as wetlands (NRC, 1992a; 19954.
A recent review of cumulative loss by Noss et al. (1995) is noteworthy for its broad scope and fine
level of distinction with which it treats habitat types and locations. Noss et al. acknowledged that the
information needed to provide uniform geographic coverage is missing, and that habitat destruction is
better catalogued in the eastern United States than elsewhere.
The discussion of cumulative losses that follows should be read with three considerations.
27
First, habitat that is degraded or lost is not necessarily biologically depauperate. For example, grazed
western grasslands and shrub steppe still support wildlife), just not the diversity that inhabited those
lands before grazing. Second, even habitat that is not considered degraded or lost might not be able to
support the abundance and variety of species that it once did. Such habitat might be used for recreation
or other activities, or simply little of it might be left. Moreover, some habitats are fragmented or of
such small area that they might no longer include the habitats required by some specialized species or
might be below the critical area needed to support species with large home ranges. Finally, air or
water pollution and climate change might be affecting the viability of habitat too subtly for the
consequences to be revealed in surveys.
Cumulative losses of wetlands have attracted much concern and scrutiny (NRC, 1992a),
perhaps because 50% of animals and 33 % of plants listed as endangered or threatened under the
Endangered Species Act depend on wetland habitats (Nelson, 19891. Although wetlands comprise only
a small percentage of the U.S. land area, they have been prime sites for conversion to agriculture or
urban sprawl. According to the National Research Council (NRC, 1992a), approximately 30% (117
million acres) of U.S. wetlands have been converted (53 %, if Alaska is excluded). In some regions
and for some types of wetlands, the losses have been more severe. For example, California has lost at
least 80% of its interior and coastal wetlands (Jensen et al., 1993~. More than 85 % of the flow of
inland waters is now artificially controlled, and 98 % of stream reaches has been degraded enough to be
unworthy of federal designation as wild or scenic rivers (Benke, 19901.
The cumulative losses of terrestrial and aquatic habitat reviewed by Noss et al. (1995) included
27 specific habitats that they classified as "critically endangered" (greater than 98% cumulative
destruction). Those habitats included longleaf pine forests in the southeastern coastal plain, tall-grass
prairie east of the Missouri River, dry prairie in Florida, native grasslands in California, and old-
growth pine forests in Michigan. Other habitats, classified as endangered (between 85 % and 98 %
cumulative destruction) included old-growth forest in the Pacific Northwest and elsewhere, red spruce
forests in the central Appalachians, coastal heathland in southern New England and Long Island, all
other tall-grass prairie, vernal pools in the Central Valley and Southern California, coastal redwood
forests in California, and native shrub and grassland steppe in Oregon and Washington.
Western grasslands are considered by some to be "healthier" than they were 100 years ago, although
information is not available to assess this objectively (NRC, 19941.
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28
Science and the Endangered Species Act
Habitat loss is a direct threat to many species, and therefore important to administration of the
Endangered Species Act. Indee(l, the ESA's purpose "to provide a means whereby the ecosystems
upon which endangered species and threatened species depend may be conserved" recognizes the
importance of habitat to species, and for this reason, we return to the subject of habitat protection uncler
the ESA in Chapters 4 and 5, where we describe modern ecological concepts of habitat, cIariiFy the role
of habitat in the protection of endangered species, and suggest ways in which the act's stated purpose
can be better achieved.
Introduced Species
Much of the woricl's biota has been mollifier! by the introduction of exotic (nonnative) species.
Introcluced plant species range from an estimated 7 % of the total in Java to 28 % in Canada and 47 % in
New Zealand (Heywoo~i, 19891; introcluceti mammal species constitute about 95% of the total in New
Zealand and Hawaii but much less than 5 % in North America (Brown, 1989~. Introduced birds are
nearly 70% of the total in Hawaii (Brown, 1989), with "virtually no native land birds below 1000 m"
(Pimm, 19891. Fish are among the most wiclely introduced of vertebrates; in many cases, their
introductions were deliberate, as vividly described for the western United States by Lampman (19461.
Even in continental areas, exotic fishes can constitute large fractions of the total number of species and
have deleterious effects (Courtenay and Stauffer, 19841. For example, in California, 47 species of a
total of i l2 freshwater ant} anadromous species are introduce (Moyle, 1976~; introduced species
constitute substantial portions of the biota in other western states as well (e.g., Sigler and Sigler, 1987;
Sublette et al., 1990~.
Despite the difficulty of proving that introduced species have caused extinctions, the
circumstantial evidence is often overwhelming. Many extinctions, especially of birds and plants but
also mammals, reptiles, snails, ant} others have been attributed to introduced species, especially on
islands (Loope and Mueller-Dombois, 1989; Macclonalc3 et al., 1989; Pimm, 1989) and in their
analogs, isolated freshwater bodies (Ono et al., 19831. Groombridge (1992) considered that introclucect
species were responsible for 39% of all animal extinctions whose causes were known, and Macdonalcl
et al. concluded that 12.7% of threatened terrestrial vertebrate species on mainland areas and 31% on
islands were affected by introductions. For example, the National Research Council attributed the near
extinction of the endangered Hawaiian crow or 'Alala (Corvus hawaiiensis), to introduced predators,
introduced diseases, and habitat alteration (NRC, 1992b). The European zebra mussel (Dreissena
polymorpha) (Ricciar(ii et al., in press) and the Asiatic clam (Corbicula J?uminea) (Clarke, 1988) have
been implicated in the extinctions of species of native freshwater mussels in the United States,
especially in drainages of the Gulf of Mexico and Atlantic Ocean; those authors consider that further
extinctions are likely. Sow and Naiman (1978) and Ono et al. (1983) attributed the extinction of the
Ash Meadows (Nevacia) killifish (Empetrichthys merriami) to competition and predation from
introduced species, and Skelton (1993), Etnier and Starnes (1993), and Jenkins and Burkhead (1994)
clescribed local extirpation or near extinction of rare fish taxa by exotics and habitat degraciation in
South Africa, Tennessee, and Virginia. In the western United States and elsewhere, introduced
salmonid species have hybridized with endemic forms (Behnke, 19921. Perhaps the most notorious of
all exotic fish introductions is that of the Nile perch (Lates nitotica) into Lake Victoria in East Africa,
where it has clevastated the diversity of the endemic cichlid fishes. Estimates of extinctions there have
been complicated by habitat changes and incomplete sampling, but Witte et al. (1992) estimated that
200 species of endemic cichlid fishes (of an original total of about 300) had "already disappeared or
twere] threatened with extinction" mainly as a result of predation by the Nile perch.
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Species Extinctions: Extinctions Over Geological Time
29
In many cases, the effects of exotic species have been exacerbated by habitat degradation. For
example, loss of habitat reduced the Hawaiian crow population and made it more vulnerable to the
effects of introduced predators and diseases (NRC, 1992b). Impoundments on the Colorado River
changed the habitat to favor introduced species of fishes that compete with and prey on some native
endangered species in addition to reducing spawning habitat for the native species and advsersely
changing the water temperature (Ono et al., 1983~.
Accidental species introductions have increased with increased human mobility and are not
likely to decline in the near future. Deliberate introductions have occurred for hundreds of year and
continue despite a growing awareness of the problems they can cause and laws and regulations that
prohibit them. In a few cases, introductions are extremely well documented and studied, as for
example the various predatory species introduced into California to control the California red scale
(Aonidielia aurantii), which was itself accidentally introduced from Australia between 1868 and iS75
(Luck, 1986~. In general, the effects of introduced species are difficult to predict (NRC, 1986),
although some progress has been ma(le (Levin, 1989; Pimm, 1989; Simberioff, 1989, Ricciardi et al.,
in press). Unless they occupy small isolated areas, such as small islands or lakes, exotics are difficult
to eradicate, although control is sometimes possible if started early, especially for many vertebrates
(Groves, 1989; MacdonaId et al., 19891.
Conclusions and Recommendations
Several concepts from this chapter apply to the understanding of biological diversity and
attempts to protect it. From these concepts we draw the following conclusions.
· The current extinction event differs from extinction events in the fossil record in being less
selective, i.e., it actually or potentially involves all taxonomic groups of organisms, in any sort of
nonmarine habitat. Although the number of documented extinctions in recent years might appear to be
small as a fraction of all extant species, it is important to understand that even so-called catastrophic
extinctions took many thousands of years to occur. Thus, the appropriate focus is the rate of
extinctions, and the current extinction rate appears to significantly greater than background rates.
Available evidence suggests that the current accelerated extinction rate is largely human-caused and is
likely to increase rather than decrease in the near future.
~ Both modern and prehistoric human activities, especially those associated with agriculture
and urbanization, have altered natural ecosystems such as forests, lakes, prairies, and floodplains
through the reduction or loss of certain species of plants and animals, the propagation of others, and
modifications of landscape, soils, and water supply.
~ On islands, including those that are a part of or affiliated with the United States, a relatively
high percentage of species has become extinct or endangered because of both modern and prehistoric
human activities. Direct human predation, predation from introduced mammals (such as rats, dogs,
pigs), habitat changes (deforestation, urbanization, agriculture, exotic plants), and introduced pathogens
(such as avian pox and avian malaria) account for these extinctions. Because island biotas already have
lost so many populations and species and land resources are so limited, conservation programs on
islands face an extraordinary challenge to maintain conditions that will allow the long-term survival of
. . .
existing species.
~ The prehistoric and ongoing extinction of so many populations and species of birds on
islands has consequences beyond losing the birds themselves. The losses of land birds, for example,
may influence pollination or seed dispersal of indigenous plants.
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30
Science and the Endangered Species Act
Based on these conclusions ant! as substantiates! within this chapter, we make these
recommendations .
· Because we can relate many biotic events to abiotic events in earth history with reasonable
accuracy, our knowledge of the past is important for predicting biotic responses to future changes in
climate and other physical phenomena. Therefore, when feasible, conservation decisions should
consider long-term impacts as revealed by our improved understanding of the earth's physical and
biotic history.
~ The natural and anthropogenic processes affecting extinctions ant! speciation operate at
various time scales. To understand the potential long-term impacts of the current extinction event, the
process of extinction should be examined across these time scales. Extinction rates that seem low on
first inspection could in fact result in major losses of species if evaluated on longer time scales.
· There are three primary anthropogenic processes that lead to species endangerment and
extinction overharvesting; the introduction of nonnative species, including the spread of disease; and
habitat destruction. For most endangered species in the United States today, the most serious threat is
habitat destruction. Because of this, habitat conservation is the best single means to counter extinction.
Introduced species also present a significant threat. Policies that prevent deliberate introductions and
reduce the adverse effects of acciclental introductions should be encouraged.
REFERENCES
Allen, J. D., and A. S. FIecker. 1993. Biocliversity conservation in running waters. BioScience
43 :32-43.
Appenzeller, T. 1993. Ancient climate coolings are on thin ice. Science 262: IS18-~19.
Bates, C. D., I. A. Hamber, and M. I. Lee. 1993. The California Condor and the California Indians.
American Indian Art 19:40-47.
Behnke, R. I. 1992. Native Trout of Western North America. American Fisheries Society, Bethesda,
Md.
Benke, A. C. 1990. A perspective on America's vanishing streams. I. Am. Benthol. Soc. 9~:77-78.
Benton, M. J. 1995. Diversification ant! extinction in the history of life. Science 268:52-58.
Betancourt, I. L., I. S. Dean, and H. N. Hull. 1986. Prehistoric long-distance transport of
construction beams, Chaco Canyon, New Mexico. American Antiquity 51:370-375.
Betancourt, I. L. and T. R. Van Devencler. 1981. Holocene vegetation in Chaco Canyon, New
Mexico. Science 214:656-658.
Betancourt, I. L., T. R. Van Devender, and P. S. Martin, eds. 1990. Packrat Middens: The Last
40,000 Years of Biotic Change. University of Arizona Press, Tucson.
Brown, I. H. 1989. Patterns, Modes and Extents of Invasions by Vertebrates. Pp. 85-109 in I. A.
Drake, H. A. Mooney, F. di Castri, R. H. Groves, F. J. Kruger, M. Rejmanek, and M.
Williamson. Eds. Biological Invasions: A Global Perspective. SCOPE 37. John Wiley &
Sons, Chichester, U.K.
gurney, D. A. 1993. Recent animal extinctions: recipes for disaster. American Scientist 81 :530-541.
Clarke, A. H. 1988. Aspects of Corbiculid-Unionid sympatry in the United States. Malacology Data
Net 2 (3/4):57-99.
Cook, R. E., and P. Dixon. 1989. A review of recovery plans for threatened and endangered plant
species. World Wildlife Fund Report, Washington, D.C.
OCR for page 31
Species Extinctions: Extinctions Over Geological Time
31
Courtenay, W. R., Jr., and J. R. Stauffer, Jr. 1984. Distribution, Biology, and Management of Exotic
Fishes. The Johns Hopkins University Press, Baltimore, Md.
Currier, M. J. P. 1983. Fells concolor. Mammalian Species no. 20.
Dansgaard, W., S. J. Johnsen, H. B. CIausen, D. DahI-Jensen, N. S. Gundestrup, C. U. Hammer, C.
S. Hvidberg, J. P. Steffensen, A. E. Sveinbjornsdottir, J. Jouzel, and G. Bond. 1993.
Evidence for general instability of past climate from a 250-kyr ice-core record. Nature
364:218-220.
Deyrup, M., and R. Franz (eds). 1994. Rare and Endangered Biota of Florida. Volume 4:
Invertebrates. University Press of Florida.
Diamond, J. 1992. The Third Chimpanzee. Harper Collins, New York.
Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1992. Birds in Jeopardy. Stanford University Press,
Stanford, Ca.
Emslie, S. D. 1987. Age and diet of fossil California Condors in Grand Canyon, Arizona. Science
237:768-770.
Emslie, S. D. 1990. Additional i4C dates on fossil California Condor. National Geographic Research
6: 134-135.
Engbring, J. and H. D. Pratt. 1985. Endangered birds in Micronesia: Their history, status, and
future prospects. pp. 71-105 in S. A. Temple, ed. Bird Conservation 2. University of
Wisconsin Press, Madison.
Etnier, D. A., and W. C. Starnes. 1993. The Fishes of Tennessee. University of Tennessee Press,
Knoxville.
Franklin, J., and D. W. Steadman. 1991. The potential for conservation of Polynesian birds through
habitat mapping and species transiocation. Conservation Biology 5:506-521.
GRIP (GreenIand Ice-core Project). 1993. Climate instability during the last interglacial period
recorded in the GRIP ice core. Nature 364:203-207.
Groombridge, B. (ed.) 1992. GIobal Biodiversity: Status of the Earth's Living Resources. Chapman
and Hall, New York.
Grootes, P. M., M. Stuiver, J. W. C. White, S. Johnsen, and J. Jouzel. 1993. Comparison of oxygen
isotope records from the GISP2 and GRIP GreenIand ice cores. Nature 366:552-554.
Guthrie, D. A. 1992. A late Pleistocene avifauna from San Migue! Island, California. Natural
History Museum of Los Angeles County, Science Series 36:319-327.
Heywood, V. H. 1989. Extents and Modes of Terrestrial Invasions by Plants. Pp. 31-60 inJ. A.
Drake, H. A. Mooney, F. di Castri, R. H. Groves, F. J. Kruger, M. Rejmanek, and M.
Williamson. Eds. Biological Invasions: A GIobal Perspective. SCOPE 37. John Wiley &
Sons, Chichester, U.K.
Imbrie, J., and K. P. Imbrie. 1979. The Ice Ages: Solving the Mystery. EnsIow Publishers, Hiliside,
N.J.
Jablonski, D. 1989. The biology of mass extinction: Apaleontologicalview. Phil. Trans. Royal Soc.
London. B 325: 357-368.
Jablonski, D. 1991. Extinctions: A paleontological perspective. Science 253:754-757.
James, H. F., and S. L. Olson. 1991. Descriptions of thirty-two species of birds from the Hawaiian
Islands: part II. Passeriformes. Ornithological Monographs 46:~-~.
James, H. F., T. W. Stafford, Ir., D. W. Steadman, S.L. Olson, P. S. Martin, A. I. T. Jull, and P.
McCoy. 1987. Radiocarbon dates on bones of extinct birds from Hawaii. Proceedings of the
National Academy of Sciences USA 84:2350-2354.
lenkins, R. E., and N. M. Burkheaci. 1994. Freshwater Fishes of Virginia. American Fisheries
Society, Bethesda, Md.
OCR for page 32
32
Science and the Endangered Species Act
Kerr, R. A. 1993a. The whole work! hac! a case of the Ice Age shivers. Science 262: 1972-1973.
Kerr, R. A. 1993b. A bigger cleath knell for the dinosaurs? Science 261:1518-1519.
Klein, R. G. 1984. Mammalian extinctions and Stone Age people in Africa. pp. 553-573 in P. S.
Martin and R. G. Klein, eds. Quaternary Extinctions. University of Arizona Press, Tucson.
Klein, R. G. 1992. The Impact of Early People on the Environment: The Case of Large Mammal
Extinctions. Pp. 13-34 in J. E. Jacobsen and J. Firor, eds. Human Impact on the
Environment: Ancient Roots, Current Challenges. Wheatview Press, Boulder, Co.
Lampman, B. H. 1946. The Coming of the Pond Fishes. Binfords & Mort, Portland, Or.
Levin, S. A. 1989. Analysis of Risk anti Invasions and Control Programs. Pp. 425-435 ins. A.
Drake, H. A. Mooney, F. Eli Castri, R. H. Groves, F. I. Kruger, M. Rejmanek, and M.
Williamson. Eds. Biological Invasions: A Global Perspective. SCOPE 37. John Wiley &
Sons, Chichester, U.K.
Loope, L. L., and D. Mueller-Dombois. 1989. Characteristics of Invaded Islands, with Special
Reference to Hawaii. Pp. 257-280 in I. A. Drake, H. A. Mooney, F. di Castri, R. H. Groves,
F. I. Kruger, M. Rejmanek, and M. Williamson. Eds. Biological Invasions: A Global
Perspective. SCOPE 37. John Wiley & Sons, Chichester, U.K.
Luck, R. F. 1986. Biological Control of California Red Scale. Pp. 165-~89 in NRC (National
Research Council). Ecological Knowledge and Environmental Problem-Solving: Concepts ant]
Case Studies. National Academy Press, Washington, D.C.
MacArthur, R. H., anti E. O. Wilson. 1967. The Theory of Island Biogeography. Princeton
University Press, Princeton.
Macdonald, I. A. W., L. L. Loope, M. B. Usher, and O. Hamman. 1989. Wildlife Conservation and
the Invasion of Nature Reserves by Introduced Species: a Global Perspective. Pp. 215-255 in
I. A. Drake, H. A. Mooney, F. di Castri, R. H. Groves, F. I. Kruger, M. Rejmanek, and M.
Williamson. Eds. Biological Invasions: A Global Perspective. SCOPE 37. John Wiley &
Sons, Chichester, U.K.
Markgraf, V. 1989. Palaeoclimate in Central and South America since lS,000 BP based on pollen and
lake-level records. Quaternary Science Reviews 8: 1-24.
Martin, P. S. 1984. Prehistoric overkill: The global moclel. pp. 354-403 in P. S. Martin and R. G.
Klein, eds. Quaternary Extinctions. University of Arizona Press, Tucson.
Martin, P. S. 1990. 40,000 years of extinctions of the "planet of Loom." Palaeogeography,
Palaeoclimatology, Palaeoecology 82:187-201.
Martin, P. S. and R. G. Klein, eds. 1984. Quaternary Extinctions. University of Arizona Press,
l ucson.
Martinson, D. G., N. G. Pisias, J. D. Hays, J. Imbrie, T. C. Moore, Jr., and N. J. Shackleton. 1987.
Age dating and the orbital theory of the Ice Ages: development of a high-resolution 0 to
300,000-year chronostratigraphy. Quaternary Research 27: 1-29.
Mayewski, P. A., L. D. Meeker, S. WhitIow, M. S. Twickler, M. C. Morrison, R. B. Alley, P.
Bloomfield, and K. Taylor. 1993. The atmosphere during the Younger Dryas. Science
261: 195-197.
Mech, L. D. 1974. Canis lupus. Mammalian Species no. 37.
Miller, R. R., J. D. Williams, and I. E. Williams. 1989. Extinctions of North American fishes cluring
the past century. Fisheries 14:22-38.
Morejohn, G. V. 1976. Evidence of the survival to recent times of the extinct flightless duck
Chendytes lawi Miller. Smithsonian Contributions to Paleobiology 27:207-211.
Morell, V. 1993. How lethal was the K-T impact? Science 261:1518-1519.
Moyle, P. B. 1976. Inland Fishes of California. University of California Press, Berkeley.
OCR for page 33
Species Extinctions: Extinctions Over Geological Time
33
Nadachowsk~, A. i993. The species concept and Quaternary mammals. Quaternary International
19:9-! 1.
Nelson, I. 1989. Agriculture, wetiancis, and endangered species: The Food Security Act of 1985.
Endangered Species Technical Bulletin 14:6-~.
Nitecki, M. H. and D. V. Nitecki, eds. 1986. The Evolution of Human Hunting. Plenum Press, New
York.
Noss, R. F., E. T. LaRoe IIl, and I. M. Scott. 1995. Endangered Ecosystems of the Uniter! States: A
Preliminary Assessment of Loss and Degradation. Biological Report 2S, U.S. DOI, National
Biological Service, Washington, D.C.
Nott, M. P., E. Rogers, ant! S. Pimm. 1995. Modern extinctions in the kilo-cleath range. Current
Biology 5~: 14-17.
Nowak, R. M. and I. L. Paradiso. 1983. Walker's Mammals of the World. Johns Hopkins
University Press, Baltimore.
NRC (National Research Council). 1986. Ecological Knowledge and Environmental Problem-Solving:
Concepts and Case Studies. National Academy Press, Washington, D.C.
NRC (National Research Council). 1992a. Restoration of Aquatic Ecosystems: Science, Technology,
and Public Policy. National Academy Press, Washington, D.C.
NRC (National Research Council). 1992b. The Scientific Bases for the Preservation of the Hawaiian
Crow. National Academy Press, Washington, D.C.
NRC (National Research Council). 1994. Rangelan(1 Health: new Methods to Classify, Inventory,
and Monitor Rangelands. National Academy Press, Washington, D.C.
NRC (National Research Council). 1995. Wetlands: Characteristics and Boundaries. National
Academy Press, Washington, D.C.
Olson, S. L., and H. F. lames. 1982. Fossil birds from the Hawaiian Islands: evidence for wholesale
extinction by man before Western contact. Science 217:633-635.
Olson, S. L., and H. F. lames. 1984. The role of Polynesians in the extinction of the avifauna of the
Hawaiian islands. pp. 768-780 in P. S. Martin and R. G. Klein, eds. Quaternary Extinctions.
University of Arizona Press, Tucson.
Olson, S. L., and H. F. James. 1991. Descriptions of thirty-two species of birds from the Hawaiian
Islands: part I. Non-passeriformes. Ornithological Monographs 45:~-~.
Ono, R. D., J. D. Williams, and A. Wagner. 1983. Vanishing Fishes of North America. Stone Wall
Press, Washington, DC.
Owen-Smith, N. 1987. Pleistocene extinctions: the pivotal role of megaherbivores. Paleobiology
13:351-362.
Pasitschniak-Arts, M. 1993. Ursus arctos. Mammalian Species no. 439.
Pielou, E. C. 1991. After the Ice Age. University of Chicago Press, Chicago.
Pimm, S. L. 1989. Theories of Predicting Success and Impact of Introduced Species. Pp. 351-367 in
I. A. Drake, H. A. Mooney, F. di Castri, R. H. Groves, F. I. Kruger, M. Rejmanek, and M.
Williamson. Ells. Biological Invasions: A Global Perspective. SCOPE 37. John Wiley &
Sons, Chichester, U.K.
Pirazzoli, P. A. 1993. Global sea-level changes and their measurement. Global and Planetary Change
S: 135-148.
Plummer, L. N. 1993. Stable isotope enrichment in paleowaters of the southeast Atlantic coastal
plain, United States. Science 262:2016-2020.
Rampino, M. R. and S. Self. 1992. Volcanic winter and accelerated glaciation following the Toba
super-eruption. Nature 359:50-52.
Rea, A. M. 1980. Late Pleistocene and Holocene turkeys in the Southwest. Natural History Museum
OCR for page 34
34
Science and the Endangered Species Act
of LQS Angeles County, Contributions in Science 330:209-224.
Rea, A. M. 1983. Once a River. University of Arizona Press, Tucson.
Retaliack, G. I. 1995. Permian-Triassic life crisis on lanci. Science 267:77-80.
Ricciardi, A., F. G. Whoriskey, and J. B. Rasmussen. In press. Predicting the density and impact of
Dreissena infestation on native unionid bivalves from Dreissena field density. Can. J. Fish.
Aquat. Sci.
Schorger, A. W. 1955. The Passenger Pigeon: Its Natural History and Extinction. University of
Wisconsin Press, Madison.
Semken, H. A., Ir. 1983. Holocene mammalian biogeography and climatic change in the eastern and
central United States. pp. iS2-207 in H. E. Wright, ed. Late-Quaternary Environments of the
United States, vol. 2. University of Minnesota Press, Minneapolis.
Shackleton, N. I. 1987. Oxygen isotopes, ice volume and sea level. Quaternary Science Reviews
6:183-190.
Sharpton, V. L., K. Burke, A. Camargo-Zanoguera, S. A. Hall, D. S. Lee, L. E. Marin, G. Suarez-
Reynoso, I. M. Quezacia-Muneton, P. D. Spuclis, and J. Urritia-Fucugauchi. 1993. Chicxulub
multiring impact basin: size and other characteristics derived from gravity analysis. Science
261: 1564-1567.
Sibley, C. G. and B. L. Monroe, Ir. 1990. Distribution and Taxonomy of Birds of the Worict. Yale
University Press, New Haven.
Sigler, W. F., and I. W. Sigler. 1987. Fishes of the Great Basin: A Natural History. University of
Nevada Press, Reno.
SimberIoff, D. 1989. Which Insect Introductions Succeed anti Which Introductions Fail? Pp. 61-75 in
J. A. Drake, H. A. Mooney, F. di Castri, R. H. Groves, F. J. Kruger, M. Rejmanek, and M.
Williamson. Ells. Biological Invasions: A Global Perspective. SCOPE 37. John Wiley &
Sons, Chichester, U.K.
Simenstad, C. A., I. A. Estes, and K. W. Kenyon. 1978. Aleuts, sea otters, and alternate stable-state
communities. Science 200:403-411.
Skelton, P. 1993. A Complete Guide to the Freshwater Fishes of Southern Africa. Southern Book
Publishers, Halfway House, South Africa.
Adz, D. L., ant! R. I. Naiman. 1978. The Natural History of Native Fishes in the Death Valley
System. Science Series Publication 30. Natural History Museum of Los Angeles County, Los
Angeles, Ca.
Stafford, T. W., Ir., P. E. Hare, L. A. Currie, A. J. T. Jull, and D. J. Donahue. 1990. Accelerator
radiocarbon dating at the moelcular level. Journal of Archaeological Science 18:35-72.
Steadman, D. W. 1989. Extinction ofbircis in eastern Polynesia: a review of the record, ant}
comparisons with other Pacific island groups. Journal of Archaeological Science 16: 177-205.
Steadman, D. W. 1991. Extinction of species: past, present, and future. pp. 156-169 in R. L.
Wyman, ed. Global Climate Change and Life on Earth. Routledge, Chapman, and Hall, New
York.
Steaciman, D. W. 1992. Extinct and extirpated bircls from Rota, Mariana Islancls. Micronesica 25:71-
84.
Steaclman, D. W. 1993. Biogeography of Tongan birds before and after human impact. Proceedings
of the National Academy of Sciences USA 90:818-822.
Steaciman, D. W. In press. Ecosystem integrity: the impact of traditional peoples. Encyclopedia of
Environmental Biology. Academic Press, Inc., San Diego.
Steadman, D. W. 1995. Prehistoric extinctions of South Pacific birds: Biodiversity meets
zooarchaeology. Science 267: 1123-1131.
OCR for page 35
Species Extinctions: Extinctions Over Geological Time
35
Steadman, D. W., and P. S. Martin. 1984. Extinction of birds in the Late Pleistocene of North
America. pp. 466-477 In P. S. Martin and R. G. Klein, ects. Quaternary Extinctions.
University of Arizona Press, Tucson.
Steadman, D. W., ant! N. G. Miller. 1987. California condor associated with sprucejack pine
woodland in the Late Pleistocene of New York. Quaternary Research 28:415-426.
Steadman, D. W., T. W. Stafford, Jr., D. I. Donahue, and A. J. T. Jull. 1991. Chronology of
Holocene vertebrate extinction in the Galapagos Islands. Quaternary Research 35: 126-133.
Sublette, I. E., M. D. Hatch, and M. Sublette. 1990. The Fishes of New Mexico. University of New
Mexico Press, Albuquerque.
Swetnam, T. W. 1993. Fire history and climate change in giant sequoia groves. Science 262:~85-
889.
Thomson, K. S. 1993. Northern exposures. American Scientist 81:522-525.
Turner, A. 1993. Species and speciation. Evolution anti the fossil record. Quaternary International
19:5-8.
USFWS. 1992. Endangered and Treatenecl Species Recovery Program. Report to Congress. U.S.
Department of Interior, U.S. Fish and Wilcllife Service, Washington, D.C. December 1992.
Webb, T. Ill, P. I. Bartlein, S. Harrison, and K. H. Anderson. 1993. Vegetation, lake levels, and
climate in eastern United States since 18,000 yr B.P., In H. E. Wright, T. Webb Ill, and I. E.
Kutzbach, Ells. Global Climates Since the Last Glacial Maximum, Chap. 17. University of
Minnesota Press, Minneapolis.
Wilson, E. O. 1992. The Diversity of Life. Harvard University Press, Cambridge,
Massachusetts.
Witte, F. T., J. GoIcischmicit, I. Wanink, M. van Oijen, K. Goudswand, E. Witte-Maas, and N.
Bouton. 1992. The destruction of an endemic species flock: Quantitative data on the decline
of the haplochromine cichlicts of Lake Victoria. Environ. Biol. Fishes 34: 1-28.
Zubrow, E. 1990. The depopulation of native America. Antiquity 64:754-765.
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Representative terms from entire chapter:
chaco canyon
