From Climate Change Reconsidered, a work of the Nongovernmental International Panel on Climate Change
There is a large gap between what scientists understand about the definition and causes of extinctions and what is reported in the popular press and even in some headline-seeking scientific journals. We start our analysis by asking what we know about the causes of past extinctions, the shortcomings of popular predictions of pending extinctions due to climate change, and the phenomenon of rapid evolutionary change.
Looking at the research papers selected to support the theory of massive warming extinctions, we are struck by many biologists’ apparent misunderstanding of extinction. Some biologists seem to believe that effective conservation means every local population of butterflies and mountain flowers must be preserved. This is obviously impossible on a planet with continual, massive climate changes and human impacts. Some biologists try to define more and more local populations as separate species—a subterfuge.
A recent article in Science amply illustrates the conflicted feelings and biologists’ frantic desire to protect everything. In an article titled “All Downhill from Here,” Krajick (2004) laments the supposed danger to pikas (rodents, cousins to rabbits) that live on treeless mountaintops:
As global temperatures rise, the pika’s numbers are nose-diving in far-flung mountain ranges … researchers fear that if the heat keeps rising, many alpine plants and animals will face quick declines or extinctions … creatures everywhere are responding to warming, but mountain biota, like cold-loving polar species, have fewer options for coping. … Comprising just 3% of the vegetated terrestrial surface, these islands of tundra are Noah’s ark refuges where whole ecosystems, often left over from glacial times, are now stranded amid un-crossable seas of warm lowlands.
Krajick himself seems to forget the words in his own opening paragraph: pikas “are also some of the world’s toughest mammals.” As for his “un-crossable seas of warm lowlands,” pikas may not be able to thrive in the lowlands competition, but it does seem likely they could find enough vegetation there during their travels to tide them over until they find other, cooler mountaintops.
Parmesan and Yohe (2003) also present a distorted version of the term “extinction.” They counted Edith’s checkerspot butterflies at 115 North American sites with historical records of harboring the species and then classified the sites as “extinct or intact.” They found local checkerspot populations in much-warmer Mexico were four times more likely to be “locally extinct” than those in much-cooler Canada. Similarly, Ian Stirling, an expert on polar bears who is widely quoted in the debate over whether global warming may reduce polar bear populations, was quoted by the World Wide Fund for Nature in 2002 as saying “polar bear numbers will be reduced in the southern portions of their range [and] may even become locally extinct” (WWF, 2002). However, “locally extinct” is not a scientific term. Extinct means “no longer in existence; died out.” Gone forever. Parmesan and Yohe are using it in reference to butterfly populations that have simply moved—and even left forwarding addresses farther north. Polar bears, too, are known to migrate to different areas in response to changes in climate and competition for food. This is not extinction, but extirpation—the loss of a population in a given location. The butterflies are responding effectively to climate change—which is certainly what we would hope a butterfly species would do on a planet with a climate history as variable as Earth’s. Parmesan and Yohe found populations of Edith’s checkerspot butterflies thriving over most of western North America, but fewer of them at the southernmost extremity of their range—in Baja California and near San Diego—than in the past. However, parts of Canada have been warming into their preferred climate range.
Species resist extinction strongly and they often persist even when humans think they’ve been wiped out. The supposedly extinct ivory-billed woodpecker was recently found in two forests in eastern Arkansas (Arkansas Game and Fish Commission, 2005). The Nature Conservancy recently found three “extinct” snails in Alabama and California. Botanists have found the Mount Diablo buckwheat plant for the first time since 1936. At least 24 other “extinct” species have been found during natural heritage surveys in North America since 1974 (Holloway, 2005).
Most of the world’s major species “body types” were laid down during the Cambrian period 600 million years ago (Levinton, 1992), so we know the major species have dealt successfully through the ages with new pest enemies, new diseases, ice ages, and global warmings greater than today’s. Most wild species are at least one million years old, which means they have all been through at least six hundred 1,500-year climate cycles. Not the least of the warmings was the Holocene Climate Optimum, which was warmer than even the predictions of the IPCC for 2100 (IPCC, 2007). That very warm period ended less than 5,000 years ago.
Environmentalists argue that the speed of today’s climate change is greater than previous warmings and will overwhelm the adaptive capacities of plants and animals. Yet history and paleontology agree that many of the past global temperature changes arrived very quickly, sometimes in a few decades. For example, 12,000 years ago, the Younger Dryas event suddenly and violently swung from warm temperatures back to Ice Age levels by the shutdown of the Gulf Stream as melting water from the extra trillion tons of ice built up in the glaciers and ice sheets over the previous 90,000 years of frigid climate was released into the oceans. The shutdown of the oceans’ Atlantic Conveyor quickly triggered another thousand years of Ice Age. How did wild species deal with Mother Nature’s sudden, sharp reversals then? In another example, starting about 1840 a Wyoming glacier went from Little Ice Age cold to near present-day warmth in about a decade (Schuster et al., 2000). There’s no evidence of any local species being destroyed by that rapid temperature change.
In contrast to the missing evidence of past climate changes having caused extinctions, we already know how most of the world’s extinct species were lost, and in what order of magnitude (Singer and Avery, 2007). The first cause is huge asteroids striking the planet. The web sites of such universities as the University of California–Berkeley, Smith, and North Carolina State are replete with evidence of these “big bangs.” Earth’s collisions with massive missiles from outer space explode billions of tons of ash and debris into the planet’s atmosphere, darken the skies, and virtually eradicate growing seasons for years at a time. There apparently have been more than a dozen such collisions in the Earth’s past and they have destroyed millions of species, most of which we know about only through the fossil record.
From about 50,000 years ago until today, Eurasia lost approximately 36% of its large mammals, while North American lost 72% of its Late Pleistocene mega-fauna. However, "despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during this period remain contentious." Lorenzen et al. (2011) chose six species to investigate why some Ice Age mammals became extinct and others did not. Combining genetic, archaeological and climate data, four critical time periods were studied: pre-LGM (Last Glacial Maximum), peak LGM, end LGM and mid-Holocene. Demographic histories for each species were inferred from ancient mitochondrial DNA (control region) sequences that were analyzed three different ways: "Bayesian skyride," serial coalescent simulation and isolation-by-distance analysis.
All of the cold-adapted mammals studied by this research team managed to survive the long, relatively warm period that preceded the LGM. Once conditions improved (i.e. got colder), populations rebounded. Such bottlenecks were evident in all species except bison. The wooly rhinoceros was widely distributed across Eurasia but went extinct rapidly during the intense warming that characterized by the end of the LGM, with no evidence that humans hunters affected this outcome. Musk ox were similarly more affected by climate than by humans and while their range and population size has contracted, they have persisted despite Holocene warming (Campos et al. 2010). Woolly mammoth went extinct after the Ice Age ended but more gradually, perhaps due to a combination of climate change and human hunting.
It is significant that the study found no distinguishing characteristics in the rate or pattern of decline in those species that went extinct compared to those that have survived and that all six species survived-and rebounded from-marked declines in their populations. As the authors conclude, such outcomes emphasize "the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change."
In 2004, researchers announced that geological evidence suggests an object crashed at the shoreline of what is now Australia’s northwestern coast 251 million years ago, creating climate changes and other natural catastrophes. Gugliotta (2004) filed the following report on the discovery for the Washington Post:
Scientists said yesterday they have found evidence that a huge meteorite or comet plunged into the coastal waters of the Southern Hemisphere 251 million years ago, possibly triggering the most catastrophic mass extinction in Earth’s history. The researchers said that geological evidence suggests that an object about six miles in diameter crashed at the shoreline of what is now Australia’s northwestern coast, creating climate changes and other natural catastrophes that wiped out 90 percent of marine species and 70 percent of land species.
The second known cause of extinctions is hunting. For a million years or so, humans along with Homo erectus in Southeast Asia and Neanderthals in Europe have hunted whatever they could kill. If it went extinct, we hunted something else. In this sense, the last Ice Age did cause some indirect species extinctions. During that extremely cold period, so much of the world’s water was trapped in ice caps and glaciers that sea levels dropped as much as 400 feet below today’s levels. Stone Age hunters walked across the Bering Strait from Asia and found hordes of wild birds and mammals that did not fear man. More than 40 edible species were wiped out in a historical eye-blink, including North America’s mammoths, mastodons, horses, camels, and ground sloths (Diamond, 1997).
A similar spate of human-hunter extinctions recently has been confirmed in Australia by the discovery of a cave full of fossils beneath the Nullabor Plain. The new fossils disarm the claim that a huge number of Australian species—including its marsupial lion, claw-footed kangaroo, giant wombat, and the Genyornis, the heaviest bird ever known—went extinct 46,400 years ago because of climate change. The discovery team said the species found in the cave died during a dry climate similar to today’s, which hadn’t changed in 400,000 years. However, the fire-sensitive woodlands, to which the species were adapted, disappeared suddenly about 46,000 years ago—apparently because the newly arrived aboriginal people burned the woods to drive game into the arms of club-wielding hunters. The landscape was reshaped by fire from woods to shrubbery (Western Australian Museum, 2007).
Third: Man learned to farm. Farming for food made us less likely to hunt wild animals and birds to extinction, but eventually we claimed one-third of all the Earth’s land area for agriculture. The saving grace was that the best land for farming tended to have few species; instead it had large numbers of a few species, such as bison on the American Great Plains and kangaroo in the Australian grasslands. In contrast, researchers have found as many species in five square miles of the Amazon as in the whole of North America. Fortunately, man tended to farm the best land for the highest sustainable food yields, leaving much of the poorer land (with its diversity) for nature (Avery, 2000).
Fourth: Alien species. Mankind’s ships, cars, and planes transport species across natural barriers, enabling them to reproduce and compete with native species. This has made the survival competition among species much more global. Island species, in particular, have found themselves in more intense competition and many have gone extinct.
These four explanations for the major extinctions of the past are each now well documented and understood. The claim that changes in temperature during the twentieth century—which the IPCC calls unprecedented in the past two millennium—are causing extinctions is much more dubious, as we see in the next section.
Theories of Contemporary Extinctions
In striking contrast to the four known causes of past extinctions, which are backed by extensive fossil and archeological evidence, Thomas et al. (2004) simply asserted the theory that raising or lowering the Earth’s temperature would cause major wildlife extinctions on a linear model. Accordingly, small temperature changes lead to relatively small reductions in species numbers while larger temperature increases drive more species to extinction. The team first defined “survival envelopes” for more than 1,100 wildlife species—in Europe, the Brazilian Amazon, the wet tropics of northeastern Australia, the Mexican desert, and the southern tip of South Africa. Then they used a “power equation” to link loss of habitat area with extinction rates. If the equation showed that a species’ potential habitat was projected to decline, it was regarded as threatened; the greater the expected habitat loss, the greater the threat. There was no provision for species adaptation or migration.
One of the Thomas team’s “moderate” scenarios was an increase in Earth’s temperature of 0.8º C in the next 50 years. The researchers said this would cause the extinction of roughly 20 percent of the world’s wild species, perhaps one million of them. Fortunately, this prediction can easily be checked. The Earth’s temperature has already increased 0.8º C over the past 150 years. How many species died out because of that temperature increase? None that we are aware of.
The Thomas paper tells us in its opening sentence: “Climate change over the past 30 years has produced numerous shifts in the distributions and abundances of species, and has been implicated in one species-level extinction.” The scientists who are predicting that 0.8º C of warming would cause hundreds of thousands of wildlife species extinctions over the next 50 years concede that this level of temperature increase over the past 150 years has resulted in the extinction of one species.
Reality takes away even that one extinction claim. Thomas et al.’s single cited example of a species driven extinct by the recent warming is the Golden Toad of Costa Rica. That was based on a 1999 paper in Nature by J. Alan Pounds and coauthors (Pounds et al., 1999) describing research conducted at the Monteverde Cloud Forest Preserve in Puntarenas, Costa Rica. Pounds et al. claimed that, due to rising sea surface temperatures in the equatorial Pacific, 20 of the 50 species of frogs and toads (including the Golden Toad) had disappeared in a cloud forest study area of 30 square kilometers. (Cloud forests are misty habitats found only in the mountains above 1,500 meters, where the trees are enclosed by cool, wet clouds much of the time. The unusual climate serves as a home to thousands of unique plants and animals.) Pounds and a coauthor explained his thesis to a scientific conference in 1999:
In a cloud forest, moisture is ordinarily plentiful. Even during the dry season … clouds and mist normally keep the forest wet. Trade winds, blowing in from the Caribbean, carry moisture up the mountain slopes, where it condenses to form a large cloud deck that surrounds the mountains. It is hypothesized that climate warming, particularly since the mid-1970s, has raised the average altitude at which cloud formation begins, thereby reducing the clouds’ effectiveness in delivering moisture to the forest. … Days without mist during the dry season … quadrupled over recent decades (Pounds and Schneider, 1999).
Pounds said at least 22 species of amphibians have disappeared from the cloud forest. Although the other species that disappeared were known to exist in other locations, the Golden Toad lost its only known home. However, two years after Pounds hypothesized that the amphibians lost their cloud forest climate to drying from sea surface warming, another research team demonstrated that it was almost certainly the clearing of lowland forests under the cloud forest of Monteverde that changed the pattern of cloud formation over the Golden Toad’s once-mistier home. Lawton et al. (2001) noted that trade winds bringing moisture from the Caribbean spend five to 10 hours over the lowlands before they reach the Golden Toad’s mountain home in the Cordillera de Tileran. By 1992, only about 18 percent of the original lowland vegetation remained. The deforestation reduced the infiltration of rainfall, increased water runoff, and thus reduced soil moisture. The shift from trees to crops and pasture also reduced the amount of water-holding canopy.
In March 1999, the Lawton team got satellite imagery showing that late-morning dry season cumulus clouds were much less abundant over the deforested parts of Costa Rica than over the nearby still-forested lowlands of Nicaragua. To check their conclusion, the Lawton team simulated the impact of Costa Rican deforestation using Colorado State University’s Regional Atmospheric Modeling System. The computer modeling showed that the cloud base over pastured landscape rose above the altitude of the Cordillera peaks (1,800 meters) by late morning. Over forests, the cloud base didn’t reach 1,800 meters until early afternoon. Lawton says these values “are in reasonable agreement with observed cloud bases in the area.” That puts the blame for the cloud forest dryness squarely on the farmers and ranchers who cleared the lowlands. Pounds’ own paper noted deforestation as a major threat to mountain cloud forests. The Lawton study leaves the Thomas team’s big computerized study of mass species extinction without any evidence that moderate climate changes—even when abrupt—cause species extinctions.
The two other articles in Nature also failed to report any evidence of extinctions caused by the recent warming trend. The closest thing to an extinction threat in the Root et al. studies was the expansion of red foxes into the southern former range of arctic foxes in North America and Eurasia. However, this is displacement/ replacement, not extinction. Hersteinsson and Macdonald (1992) concluded that the changes in fox ranges were driven by prey availability. The arctic foxes are found primarily in the treeless regions of the Arctic, where they feed on lemmings and voles in the summer and eat heavily from seal carcasses in the winter. The larger red foxes eat a wider range of prey and fruits and are regarded as stronger competitors in forest and brush land. However, they are less well camouflaged for the winters in the treeless tundra than the arctic foxes in their blue-white winter pelts. Warming temperatures have allowed trees, brush, and red foxes to move farther north in the past 150 years—but they also have allowed arctic foxes to retain enough land and prey to succeed north of the red foxes. We do not know what would have happened if there had been no northern habitat and prey to support the arctic foxes during a red fox expansion, but the foxes already have survived more radical warming than they have faced recently. In earlier parts of the interglacial period, the Arctic temperatures were 2º to 6º C higher than they are now (Taira, 1975; Korotsky et al., 1988).
Returning to the study of Thomas et al. one more time, it is interesting to note that an earlier study by Thomas contained findings that completely discredit the thesis on which the 2004 claim rests—that species have readily defined “survival envelopes” outside which they cannot survive. The Thomas team began its 2001 paper by restating the long-believed and broadly held concept that many animals are “relatively sedentary and specialized in marginal parts of their geographical distributions.” Thus, creatures are “expected to be slow at colonizing new habitats.” Despite this belief, however, the Thomas team cites its own and many other researchers’ studies showing that “the cool margins of many species’ distributions have expanded rapidly in association with recent climate warming.” This mildly undercuts their thesis. Much worse was to come. The two butterfly species the authors studied “increased the variety of habitat types that they can colonize” and the two species of bush cricket they studied showed “increased fractions of longer-winged (dispersive) individuals in recently founded populations.” The longer-winged crickets would be able to fly farther in search of new habitat.
As a consequence of the new adaptations, the Thomas authors report, “Increased habitat breadth and dispersal tendencies have resulted in about 3 to 15-fold increases in [range] expansion rates, allowing these insects to cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started.” The changes in the butterfly and cricket populations render Thomas’s entire thesis of “survival envelopes” inadequate at best and quite likely irrelevant. Yet this paper was not only written before the Root analysis, it was included in the Root analysis as one of the select few research studies supporting the mega-extinction theory.
Buried in the IPCC report are admissions that the computer models based on the dubious notion of “survival envelopes” that it relies on produce “a picture of potential impacts and risks that is far from perfect, in some instances apparently contradictory” (p. 239) and “climate envelope models do not simulate dynamic population or migration processes, and results are typically constrained to the regional level, so that the implications for biodiversity at the global level are difficult to infer,” citing Malcolm et al., 2002 (IPCC, 2007-II, p. 240).
Hof et al. (2011) agree with this view in an opinion article published in Global Change Biology. Climate change is assumed to be exceptional because of its supposedly unprecedented velocity, causing Earth’s plants and animals to be unable to migrate poleward in latitude or upward in altitude fast enough to avoid the consequences. Yet the authors speculate that "species may have used strategies other than shifting their geographical distributions or changing their genetic make-up" in response to climate change. "Intraspecific variation in physiological, phenological, behavioral or morphological traits may have allowed species to cope with rapid climatic changes within their ranges (Davis and Shaw, 2001; Nussey et al., 2005; Skelly et al., 2007).” What is clear to the researchers is that "habitat destruction and fragmentation, not climate change per se, are usually identified as the most severe threat to biodiversity (Pimm and Raven, 2000; Stuart et al., 2004; Schipper et al., 2008),” suggesting that addressing habitat destruction and fragmentation, rather than climate change, should take center stage when it comes to striving to protect Earth's biosphere.
A 2011 study published in Science, conducted by Chen et al., employed meta-analysis on studies of latitudinal range shifts of 763 species in Europe, North America, and Chile and studies of elevational range shifts for 1,367 species in Europe, North America, Malaysia, and Marion Island. The results "estimated that the distributions of species have recently shifted to higher elevations at a median rate of 11.0 meters per decade, and to higher latitudes at a median rate of 16.9 kilometers per decade." These rates are approximately two and three times faster than previously reported by Parmeson and Yohe (2003). In addition, they found that "the distances moved by species are greatest in studies showing the highest levels of warming, with average latitudinal shifts being generally sufficient to track temperature change." Even more interesting, however, were their observations that "for latitudinal studies, on average 22% of the species actually shifted in the opposite direction to that expected," and that in the altitude studies "25% of species shifted downhill rather than to higher elevations" in response to warming. This study demonstrates that many species are well-equipped to respond to changing climatic conditions.
Data on Contemporary Species
What does real-world data say about rates of extinction? In 2002, the United Nations Environmental Program (UNEP) published a new World Atlas of Biodiversity (Groombridge and Jenkins, 2002). It reported that the world lost only half as many major wild species in the last three decades of the twentieth century (20 birds, mammals, and fish) as during the last three decades of the nineteenth century (40 extinctions of major species). In fact, UNEP said the rate of extinctions at the end of the twentieth century was the lowest since the sixteenth century—despite 150 years of rising world temperatures, growing populations, and industrialization.
There is a wealth of data to support the fact that many species have prospered during the twentieth century, starting with research conducted by those who claim rising temperatures have caused a rise in extinctions. Parmesan and Yohe (2003) examined the northern boundaries of 52 butterfly species in northern Europe and the southern boundaries of 40 butterfly species in southern Europe and North Africa over the past century. Given the 0.8º C warming of Europe’s temperatures over that period, it is striking to have Parmesan and Yohe tell us that “nearly all northward shifts involved extensions at the northern boundary with the southern boundary remaining stable.” Thus, in the researchers own words, “most species effectively expanded the size of their ranges.”
Chris Thomas and a coauthor in a study published in 1999 documented changes in the distribution between 1970 and 1990 of many British bird species (Thomas and Lennon, 1999). He found that the northern margins of southerly species shifted northward by an average of 19 km, while the southern margins of northerly species remained unchanged.
On 26 high mountain summits in the middle part of the Alps, a study by Grabherr et al. (1994) of the plant species found “species richness has increased during the past few decades, and is more pronounced at lower altitudes.” In other words, the mountaintops show little loss of biodiversity at upper elevations, and increased species richness at lower elevations, where plants from still-lower elevations extended their ranges upward.
Pauli et al. (1996) examined the summit flora on 30 mountains in the European Alps, with species counts that ranged back in history to 1895. They report that mountaintop temperatures have risen by 2º C since 1920, with an increase of 1.2º C in just the last 30 years. Nine of the 30 mountaintops showed no change in species counts, but 11 gained an average of 59 percent more species, and one mountain gained an astounding 143 percent more species. Did historic species get crowded out by the flood of new warmer-zone plants? The 30 mountains showed a mean species loss of 0.68 out of an average of 15.57 species. There was no documentation that any of the species “lost” on particular mountains represented extinctions rather than local disappearances.
Vesperinas et al. (2001) reported that native heat-sensitive plant species have responded to temperature increases in the Iberian Peninsula and the Mediterranean coast over the past 30 years by expanding their ranges “towards colder inland areas where they were previously absent.”
Van Herk et al. (2002) reported that the number of lichen species groups present in the Central Netherlands increased from 95 in 1979 to 172 in 2001 as the region warmed. The researchers found the average number of species grouped per site increased from 7.5 to 18.9. Again, more warmth produced increased species richness.
Looking at the distribution of 18 butterfly species widespread and common in the British countryside, “nearly all of the common species have increased in abundance [during the warming], more in the east of Britain than in the west” according to a research team led by Emie Pollard of Britain’s Institute of Terrestrial Ecology (Pollard et al., 1995).
Warm-water species of plankton rapidly responded to warming and cooling in the western English Channel, shifting latitudinally by up to 120 miles, and increasing or decreasing their numbers by two to three-fold over 70 years, according to research by A.J. Southward of Britain’s Marine Biological Association (Southward, 1995).
In the Antarctic, Adelie penguins need pack ice to thrive, whereas chinstrap penguins prefer ice-free waters. R.C. Smith et al. (1994) found that the Adelie penguins in the West Antarctic Peninsula are declining because the warming on the peninsula favors the chinstraps. Meanwhile the chinstraps in the Ross Sea region are suffering because 97 percent of Antarctica—the part that isn’t the peninsula—is getting colder. This can hardly be surprising. Two varieties of a highly mobile species have moved to the sites that favor their respective feeding and breeding requirements while their populations decline in the unfavorable sites.
The Antarctic’s only two higher-level plant species have responded to the Antarctic Peninsula’s warming by increasing their numbers at two widely separated localities (Smith, 1994). Fortunately, it would take thousands of years of increased warming to melt all the Antarctic ice and a very long period of extended cold to close all the open water around the Antarctic Peninsula. The 1,500-year climate cycle makes it almost certain that Antarctica’s plants and penguins will continue to adapt rather than disappear.
Invertebrates in a rocky intertidal site at Pacific Grove, California can’t move, but their populations change. The invertebrates were surveyed by Saragin et al. (1999) in 1931–1933 and again in 1993–1996 after a warming of 0.8º C. Ten of the 11 southern species increased in abundance, whereas five of seven northern species decreased.
New photographs were taken by Sturm et al. (2001) to match a set of 1948–1950 photographs of the Brooks Range and the Arctic coast of Alaska. At more than half of the matched locations, researchers found “distinctive and, in some cases, dramatic increases in the height and diameter of individual shrubs … and expansion of shrubs into previously shrub-free areas.”
Western American bird species are pioneering and expanding their ranges over vast areas and huge climatic differences as the climate warms. N.K. Johnson of the University of California–Berkeley compiled records for 24 bird species from Audubon Field Notes, American Birds and other sources (Johnson, 1994). He found “four northern species have extended their ranges southward, three eastern species have expanded westward, fourteen southwestern or Mexican species have moved northward, one Great Basin-Colorado Plateau species has expanded radially, and two Great Basin-Rocky Mountain subspecies have expanded westward.”
Brommer (2004) studied the birds of Finland, which were categorized as either northerly (34 species) or southerly (116 species). Brommer quantified changes in their range margins and distributions from two atlases of breeding birds, one covering the period 1974-79 and one covering the period 1986-89, in an attempt to determine how the two groups of species responded to what he called “the period of the earth’s most rapid climate warming in the last 10,000 years.” Once again, it was determined that the southerly group of bird species experienced a mean poleward advancement of their northern range boundaries of 18.8 km over the 12-year period of supposedly unprecedented warming. The southern range boundaries of the northerly species, on the other hand, were essentially unmoved, leading once again to range expansions that should have rendered the Finnish birds less subject to extinction than they were before the warming.
Similar results were obtained in a study by Hickling et al. (2005) of changes in the northern and southern range boundaries of 37 non-migratory British dragonfly and damselfly species between the two 10-year periods 1960-70 and 1985-95. All but two of the 37 species increased the sizes of their ranges between the two 10-year periods, with the researchers reporting that “species are shifting northwards faster at their northern range margin than at their southern range margin,” and concluding that “this could suggest that species at their southern range margins are less constrained by climate than by other factors,” which surely appears to be the case.
Chamaille-Jammes et al. (2006) studied four unconnected populations of a small live-bearing lizard that lives in peat bogs and heath lands scattered across Europe and Asia, concentrating on a small region near the top of a mountain in southeast France at the southern limit of the species’ range. There, from 1984 to 2001, they monitored a number of life-history traits of the populations, including body size, reproductive characteristics, and survival rates, during which time local air temperatures rose by approximately 2.2°C. In doing so, they observed that individual body size increased dramatically in all four populations over the 18-year study period in all age classes and, in the words of the researchers, “appeared related to a concomitant increase in temperature experienced during the first month of life.” As a result, since fecundity is strongly dependent on female body size, they found that “clutch size and total reproductive output also increased.” In addition, they learned that “adult survival was positively related to May temperature.”
In discussing their findings, the French researchers say that since all fitness components investigated responded positively to the increase in temperature, “it might be concluded that the common lizard has been advantaged by the shift in temperature.” This finding, as they describe it, stands in stark contrast to what they call the “habitat-based prediction that these populations located close to mountaintops on the southern margin of the species range should be unable to cope with the alteration of their habitat.” They conclude that “to achieve a better prediction of a species persistence, one will probably need to combine both habitat and individual-based approaches,” noting, however, that individual responses, such as those documented in their study (which were all positive), represent “the ultimate driver of a species response to climate change.”
The Audubon Society (2009) released a report in February 2009 calling attention to the correlation between the movement of North American bird populations and an increase in average January temperatures in the lower 48 U.S. states from 1969 to 2005. The report breathlessly recounted the expansion of the northern boundaries of the habitats of 58 percent of observed species of birds over the past four decades and concluded that “we must act decisively to control global warming pollution to curb the worst impacts of climate change, and take immediate steps to help birds and other species weather the changes we cannot avoid.” But the study did not ask whether the warming that occurred during this period benefitted or hurt most bird populations by moving poleward the northern edge of their habitats. One might suppose the net effect would be beneficial, and in fact this is what Audubon itself found but failed to mention in the body of the report. In a data table presented in an appendix to the report, one finds that 120 of the 305 species reported in the study (39 percent) showed statistically significant population increases, 128 (42 percent) showed no change, and only 57 (19 percent) showed statistically significant declines. These numbers suggest that North American bird species overall benefited from the modest warming from 1969 to 2005.
Euphausiids are small pelagic shrimplike crustaceans that constitute "an important component of the pelagic realm," where they "graze directly on phytoplankton and provide a food source for a range of predators including birds, seals, baleen whales and many commercially important fish species.” Using a generalized additive model, Letessier et al. (2011) assessed the influence of physical, chemical and biological variables on euphausiid species abundance associated with environmental changes based on the IPCC’s A1B climate scenario. The three UK researchers reported that "the main drivers of species abundance, in order of decreasing importance, were sea surface temperature (SST, explaining 29.53% of species variability), salinity (20.29%), longitude (-15.01%, species abundance decreased from West to East), distance to coast (10.99%) and dissolved silicate concentration (9.03%)."
Based on the IPCC’s temperature predictions, Letessier et al. say their results suggest that "the present broad patterns apparent in species abundance (low in high latitudes, high in intermediate latitudes and intermediate in the tropics) will become less pronounced in a warming ocean," and that, eventually, "species abundance will be enhanced within intermediate-to-high latitudes (30°N to 60°N and 30°S to 60°S) and diminished in the tropics (20°N to 20°S).” Given their roles as a significant food source, such shifts in euphausiid species abundance may well be viewed as a positive development.
Caribou are considered vulnerable to the effects of predicted global warming, thus efforts have recently intensified to monitor and quantify caribou populations. The Beverly barren-ground herd that migrates annually between northern Saskatchewan to Nunavut, Canada, recently became the topic of special concern. Aerial surveys in 2009 revealed only a few Beverly cows had arrived on their traditional summer calving grounds. The herd, which once numbered over 250,000 animals, appeared to have simply vanished after a few short years of ever-increasing declines. Global warming was one suggested culprit, although mining activity and hunting were also blamed.
Nagy et al. (2011) conducted a comprehensive population study of several Canadian caribou subpopulations by placing radio-collars on a number of animals from 1996-2008. The results showed that the Beverly herd had simply switched to using another calving ground. The authors determined that "One barren-ground subpopulation used two calving grounds, and one calving ground was used by two barren-ground subpopulations, indicating that these caribou cannot be reliably assigned to subpopulations solely by calving-ground use. They should be classified by annual spatial affiliation among females." Although no new subpopulation estimates were provided, the authors seem to imply that previous population size declines (based on aerial surveys) may have been inflated because some caribou cows chose to give birth outside their traditional calving grounds and were not counted.
Many, and probably most, of the world’s species have benefited from rising temperatures in the twentieth century. There is very little evidence of any extinctions. What should be plain is that, despite predictions of extinctions based on theories and computer models, real-world observations confirm that a warmer world is more, not less, hospitable to wildlife.
Additional information on this topic, including reviews of newer publications as they become available, can be found at http://www.co2science.org/subject/r/rangeexpanimals.php and http://www.co2science.org/subject/e/extinction.php.
Rapid Evolutionary Change
Skelly et al. (2007) critiqued the climate-envelope approach to predicting extinctions used by Thomas et al. (2004), citing as their primary reason for doing so the fact that this approach “implicitly assumes that species cannot evolve in response to changing climate.” As they correctly point out, “many examples of contemporary evolution in response to climate change exist,” such as populations of a frog they had studied that had “undergone localized evolution in thermal tolerance (Skelly and Freidenburg, 2000), temperature-specific development rate (Skelly, 2004), and thermal preference (Freidenburg and Skelly, 2004),” in less than 40 years. Similarly, they report, “laboratory studies of insects show that thermal tolerance can change markedly after as few as 10 generations (Good, 1993).”
Adding that “studies of microevolution in plants show substantial trait evolution in response to climate manipulations (Bone and Farres, 2001),” the researchers further noted that “collectively, these findings show that genetic variation for traits related to thermal performance is common and evolutionary response to changing climate has been the typical finding in experimental and observational studies (Hendry and Kinnison, 1999; Kinnison and Hendry, 2001).”
Although evolution will obviously be slower in the cases of long-lived trees and large mammals, where long generation times are the norm, the scientists say the case for rapid evolutionary responses among many other species “has grown much stronger,” citing, in this regard, the work of six other groups of researchers comprised of two dozen individuals (Stockwell et al., 2003; Berteaux et al., 2004; Hairston et al., 2005; Bradshaw and Holzapfel, 2006; Schwartz et al., 2006; Urban et al., 2007). As a result, they write, “on the basis of the present knowledge of genetic variation in performance traits and species’ capacity for evolutionary response, it can be concluded that evolutionary change will often occur concomitantly with changes in climate as well as other environmental changes (Stockwell et al., 2003; Grant and Grant, 2002; Balanya et al., 2006; Jump et al., 2006; Pelletier et al., 2007).”
Much the same conclusion has been reached by still other groups of scientists. In a study of the field mustard plant, for example, a group of three researchers (Franks et al., 2007) found evidence for what they describe as “a rapid, adaptive evolutionary shift in flowering phenology after a climatic fluctuation,” which finding, in their words, “adds to the growing evidence that evolution is not always a slow, gradual process but can occur on contemporary time scales in natural populations.”
Likewise, another group of researchers who published in 2007 (Rae et al., 2007)—who worked with hybrids of two Populus tree species—obtained results which, as they phrased it, “quantify and identify genetic variation in response to elevated CO2 and provide an insight into genomic response to the changing environment.” The results, they wrote, “should lead to an understanding of microevolutionary response to elevated CO2 … and aid future plant breeding and selection,” noting that various research groups have already identified numerous genes that appear sensitive to elevated CO2 (Gupta et al., 2005; Taylor, G. et al., 2005; Ainsworth et al., 2006; Rae et al., 2006).
Life in the sea, in this regard, is no different from life on land. In another study published in 2007, for example, a team of four marine biologists (Van Doorslaer et al., 2007) conducted an experiment with a species of zooplankton in which they say they “were able to demonstrate a rapid microevolutionary response (within 1 year) in survival, age at reproduction and offspring number to elevated temperatures,” and they state that “these responses may allow the species to maintain itself under the forecasted global warming scenarios,” noting that what they learned “strongly indicates rapid microevolution of the ability to cope with higher temperatures.” Many other studies, some of them cited in Section 8.3, have produced analogous results with respect to increases in temperature on corals (Kumaraguru et al., 2003; Willis et al., 2006) and increases in CO2 on freshwater microalgae (Collins et al., 2006).
While some cold-adapted mammals of the Northern Hemisphere went extinct during the cold-to-warm and warm-to-cold oscillations of climate that have occurred between the present and 60,000 years ago (kya), the musk ox (Ovibos moschatus) survived, despite their clear preference for extreme cold and dry conditions. Although musk ox were relatively abundant and widespread during the Pleistocene, they still thrive within a restricted range across the Canadian Arctic and Greenland.
Campos and her co-authors (Campos et al., 2010) used analyzed mitochondrial DNA from 149 radio-carbon dated samples of musk ox that ranged in age from approximately 56,900 years ago to the present. Known genetic sequences from modern animals (compiled previously by other researchers) were pooled with the ancient data. The results revealed that genetic diversity was high between 80-60kya, when it was relatively cold, and then declined from 50-33kya, when it had warmed up. During the Last Glacial Maximum (LGM), musk ox genetic diversity increased rapidly, only to decline steeply during the warm period leading into the Holocene (starting about 18kya).
Thus, despite a very large decrease in geographic range over time and two pronounced declines in genetic diversity, musk ox currently maintain thriving populations across the Arctic. Recovery from dramatic declines in population size and genetic diversity is clearly not only possible but has occurred more often than previously assumed (Lorenzen et al., 2011). Such results have implications for the resilience of other Arctic-adapted species that are suggested to be at future risk from the effects of anthropogenic global warming.
Melzner et al. expanded upon studies of the ability of Earth’s 30,000 species of teleost fish to maintain oxygen consumption rates and growth performance under ocean acidification conditions. In their own study (2009), Melzner et al. maintained a group of Atlantic Cod (Gadus morhua) for four months in a re-circulating aquaculture system at an atmospheric CO2 partial pressure of 0.3 kPa (3,000 ppm) and another group for 12 months at a CO2 partial pressure of 0.6 kPa (6,000 ppm), after which the fishes' swimming metabolism was investigated and tissue samples of their gills were taken for various chemical analyses.
The German scientists reported that "motor activity in adult Atlantic Cod is not compromised by long-term exposure to water PCO2 levels of 0.3-0.6 kPa," which are "scenarios exceeding the 0.2 kPa value predicted for surface ocean waters around the year 2300 (Calderia and Wickett, 2003)." They concluded that active fish species with a high ion regulatory capacity, employed to eliminate metabolic CO2, are well equipped to cope with prospected scenarios of global climate change.
Donelson et al. (2012) reared the offspring from eight wild-caught tropical damselfish Ancanthochromis polyacanthus for two generations, "in present day (+0.0°C) and predicted future increased water temperatures (+1.5°C and +3.0°C) to test their capacity for metabolic acclimation to ocean warming." After three months, they assessed the responses in resting metabolic rate relative to maximum metabolic rate for each individual to characterize changes in the ability of each fish to perform aerobic activities (which would include such functions as behavior, growth and reproduction) at normal and elevated water temperatures.
The researchers found that second generation offspring had superior metabolic performance at all temperatures when their parents had been reared to maturity at a temperature of +1.5°C or +3.0°C. In addition, one pair of damselfish (i.e. one particular genetic lineage) contributed 75% of the second generation offspring that did well at +3.0°C. Thus, in addition to acclimation occurring within two generations, there was also rapid selection of genotypes that were tolerant of higher temperatures. Donelson et al. state that "this study provides evidence that, contrary to some expectations, a tropical marine species has the capacity for acclimation and adaptation to temperature increases over timescales much shorter than the rate of anthropogenic climate change."
In conclusion, many species have shown the ability to adapt rapidly to changes in climate. Claims that global warming threatens large numbers of species with extinction typically rest on a false definition of extinction (the loss of a particular population rather than entire species) and speculation rather than real-world evidence. The world’s species have proven to be very resilient, having survived past natural climate cycles that involved much greater warming and higher CO2 concentrations than exist today or are likely to occur in the coming centuries.
Additional information on this topic, including reviews of newer publications as they become available, can be found at http://www.co2science.org/subject/e/subject_e.php under the subheading Evolution.
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