Is Climate Change Forcing Species Migration and Extinction?
Why is it news that various plants and animals are being forced out of their natural habitat because climate is changing? As demonstrated by Figure 1, climate is changing. It would be newsworthy if plants and animals weren’t reacting to changes in their environment. It would mean everything scientists have learned about biologic adaptation is wrong. It would mean that instead of changing behavior in response to environmental changes, life on earth is inflexible.
One recent example of false claims (presented to viewers of FOX cable news) is that the warming of north Atlantic waters is responsible for the appearance of a Great White Shark off the coast of Alaska. The truth is that Great Whites (Carcharadon carcharias) are endothermic – able to elevate their body temperature above that of the surrounding water. They can tolerate a broad temperature range, providing them access to prey (primarily coastal pinnipeds) over a wide ecological niche -- including sub-artic Alaskan waters. They have long been observed along the U.S. coastline from California to Alaska (Figure 9).
As for earth’s plant life, atmospheric CO2 enrichment tends to ease the potentially negative effects of rising temperatures. Studies indicate that more CO2 in the air enables plants to grow better at nearly all temperatures, but especially at higher temperatures. Elevated CO2 boosts the optimum temperature at which plants grow best and it raises the upper-limiting temperature above which plants die. Elevated CO2 makes them much more resistant to heat stress.
It appears that if the atmosphere’s temperature and CO2 concentration rise together, plants are able to adapt to the rising temperature and experience no ill effects. Under such conditions, plants living near the heat-limited boundaries of their ranges do not migrate poleward or upward towards cooler regions of the globe. At the other end of the temperature spectrum, plants living near the cold-limited boundaries of their ranges extend their ranges into areas where the temperature was previously too low for them to survive. They actually expand their ranges and overlap the similarly-expanding ranges of other plants, thereby increasing local plant biodiversity, which in turn supports increased wildlife diversity.
Amazingly, the bulk of the scientific studies that prompts media scare stories, such as those that filed the April 3, 2006 issue of TIME magazine, actually support the opposite of what often is claimed. Rather than suggesting earth's biosphere is about to suffer irreparable damage as a result of past natural warming and future predicted warming, research substantiates nearly everything known about the beneficial effects of atmospheric CO2 enrichment on plant physiology. These studies portray a biosphere of increased species richness almost everywhere on earth in response to global warming and the increase in atmospheric CO2 concentration of the past century and a half that has promoted an expansion of species' ranges throughout the entire world.
It is important to recognize that if recent changes in earth’s climate are stressing flora and fauna to the point of extinction, then natural changes in climate from year-to-year and decade-to-decade already should have killed them. Annual and decadal fluctuations are much more dramatic than the changes in average temperature observed to date. For example, if annual or decadal climate variations threaten life forms, then the huge temperature swings that occurred multiple times during the past 400,000 years (Figure 5) should already have killed off all life on earth. Obviously, such is not the case.
Nature responds differently than do models of nature’s response, as Drs. Sherwood and Craig Idso report:
“Of course plants could migrate poleward and upward at the poleward and upper bounds of their ranges, as new territories that were too cold for them in the past became more hospitable; but their warm-edge boundaries would not need to change. Likewise, there would be no need for changes in the warm-edge bounds of the ranges of animals that depend upon specific species of plants for their sustenance. And, in fact, this is precisely what scientists are discovering where there has been regional warming over the past several decades.”
In a study of shifts in the ranges of more than half a hundred European butterfly species over the past century, for example, Parmesan et al. (1999) found that most of them extended the northern boundaries of their ranges further north in response to a regional warming of approximately 0.8°C; but the southern boundaries of their ranges remained unchanged. Likewise, Thomas and Lennon (1999) studied an equally large number of British bird species from 1970 to 1990, finding that the northern boundaries of species residing in the southern part of Britain shifted northward by an average of 19 km, while the southern boundaries of species residing in the northern part of the country shifted not at all. Hence, rather than being forced to migrate and being nudged closer to extinction in response to a local increase in temperature during a period of increasing atmospheric CO2 concentration, these many butterfly and bird species actually increased their ranges and became even more protected from the possibility of extinction.
Similar phenomena have been observed in the sea. In a detailed analysis of benthic foraminifera (amoeba-like seal-dwelling organisms) in the Northeast Pacific, Cannariato et al. (1999) evaluated a sediment core to determine the effects of a number of rapid climatic changes over the course of its 60,000-year record. They found many periods of rapid temperature change, but no extinctions. In fact, they determined that the benthic ecosystems they studied "appear to be both resilient and robust in response to rapid and often extreme environmental conditions," concluding that "broad segments of the biosphere are well adapted to rapid climate change."
Nowhere can there be found a listing of all the species imagined to have gone extinct during warming over the last two centuries. On the other hand, a richness of new species continues being discovered, such as the recent find reported in the mountain rainforests of New Guinea. New species of birds, frogs, butterflies and palms were cataloged and include:
- Twenty new species of frogs
- Four new butterflies
- Five new species of palms
- The world's largest rhododendron flower
- New birds such as the wattled honeyeater; breeding grounds of the golden-fronted bowerbird and Berlepsch's six-wired bird of paradise which were thought extinct.
- A new species of tree kangaroo as well as six species of others that are rare elsewhere.
Climate change is bad (especially for polar bears). Thus, any observed associations – as apposed to model scenarios -- between polar bears and climate change are typically ignored if they don’t show the intended patterns. That is precisely the case in this instance.
Case in point, in the Baffin Bay region (the area between North America and Greenland), the temperature has been decreasing and the polar bear populations there have been in decline. In the region with the greatest temperature increase – the Pacific region between Siberia and Alaska – nearby bear populations in the North and South Beaufort Sea (just north of Alaska) have risen. Bear population and temperature have been relatively stable throughout the remaining areas. In other words, the observed relationship between temperature and bear population is the opposite of what the WWF and Time magazine reports would lead readers to believe.
Truth is that the diversity of life on earth is mute but dramatic testimony that plants and animals are readily adaptable to variations in climate. Life forms on earth actively respond to climate fluctuations with changes in their behavior and location. To paraphrase Mark Twain, “rumors of their demise are greatly exaggerated!”
For a full-length paper on the question of warming and species extinction, see (http://www.co2science.org/scripts/Template/0_CO2ScienceB2C/pdf/extinction.pdf).