Other scientific studies indicate that species are generally moving toward the poles—northward in the northern hemisphere and (with a smaller number of examples) southward below the equator. Two studies involving several thousand plant and animal species throughout the world, from plankton to polar bears, provide ample evidence that climate change is reshaping animal and plant habitats at an increasing rate.
During the fall of 2007, after the Arctic lost almost one-fourth of its ice cap in one summer, warnings regarding the demise of polar bears became more strident. "Just 10 more years of current global warming pollution trajectories will commit us to enough warming to melt the Arctic and doom the polar bear to extinction," said Kassie Siegel, director of the Center for Biological Diversity's Climate, Air, and Energy Program. "We urgently need to address global warming, not just for the sake of the polar bear but for the sake of people and wildlife around the world" (Comment Period, 2007).
Many studies suggest that habitat change is already well under way. "There is a very strong signal from across all regions of the world that the globe is warming," said Terry Root of Stanford University's Center for Environmental Science and Policy, who headed one of the research teams. "Thermometers can tell us that the Earth is warming, but the plants and animals are telling us that global warming is already having a discernible impact. People who don't believe it should take their heads out of the sand and look around" (Toner, 2003, 1-A).
Root and colleagues, in their "meta-analysis" of 143 studies, concluded,
More than 80 per cent of the species that show changes are shifting in the direction expected on the basis of known physiological constraints of species. Consequently, the balance of evidence from these studies strongly suggests that a significant impact of global warming is already discernable in animal and plant populations. The synergism [combination] of rapid temperature rise and other stresses, in particular habitat destruction, could easily disrupt the connectedness among species and lead to a reformulation of species communities, reflecting differential changes in species, and to numerous extirpations and possibly extinctions. (Root et al., 2003, 570)
Root's team and another, headed by Camille Parmesan, a biologist at the University of Texas, Austin, examined hundreds of studies describing more than 2,000 plants and animals—from shrimp, crabs, and barnacles off the Pacific coast of California to cardinals that nest in Wisconsin—to see whether they could spot the "fingerprint" of changing global temperatures (Toner, 2003, 1-A). Parmesan and Gary Yohe calculated that range shifts toward the poles had averaged 6.1 kilometers per decade, with an advance in the beginning of spring by 2.3 days per decade (Parmesan and Yohe, 2003, 37).
According to Parmesan and Yohe's analysis, some birds and butterflies had shifted as many as 600 miles northward. Grasses, trees, and other species that lack mobility have moved shorter distances. In a finding that resembled other studies, they found that springtime behavior was occurring earlier, in this case by more than two days per decade. A study of more than 21,000 swallow nests in North America, for example, indicated that the species was laying its eggs nine days earlier in the year 2000 than in 1960 (Toner, 2003, 1-A).
In mountains, various species responded to warming by moving up in elevation, seeking habitats that were similar to areas they had formerly occupied at lower altitude. In some areas, such the Great Smoky Mountains, the mountain peaks had become shrinking "islands" for cool weather species (Toner, 2003,1-A). The Root and Parmesan studies both indicated that the largest changes in temperature as well as habitat movement were taking place in the polar regions, where temperature increases have been the greatest.
"The most remarkable thing is that we have seen so many changes in so many parts of the world from a relatively small increase in temperature," Root told Mike Toner of the Atlanta Journal-Constitution. "When you consider that some people are predicting warming that would be 10 times greater by the end of this century, it's spooky to think about what the consequences might be" (Toner, 2003, 1-A). --
Alligators Moving Northward Along the Mississippi River
In mid-May 2006, alligators were sighted in the backwaters of the Mississippi River as far north as Memphis, Tennessee. "It's possible that alligators have had a northern range expansion due to the mild winters we've had in the past 10 years," wildlife agent Gary Cook said (Gators Spotted, 2006). The Tennessee Wildlife Resources Agency received reports of alligator sightings
An alligator (Jeff Dixon)
on McKellar Lake, a backwater of the Mississippi just south of Memphis, and at T.O. Fuller State Park, north of the city. Up to five alligators may have been seen, including one said to be close to 7 feet long that was reportedly spotted on a bank beside McKellar Lake. "It was just laying out in the sun," said Kay Vescovi, a chemical plant manager at a nearby industrial park, "Nobody was concerned, just kind of shocked that they're this far north" (Gators Spotted, 2006).
Stan Trauth, a zoology professor at Arkansas State University, said alligators spotted in the Memphis region might be former pets that were released into the wilds. "Moving north is not what they would want. They would want to stay in the more moderate climate," Trauth said. Trauth, who has tracked alligators released in Arkansas by wildlife agents, said the region is along the northern edge of animals' survival range. "They're reaching their physiological tolerance in the winter in this area," he said (Gators Spotted, 2006).
Armadillos Spreading Northward
The armadillo (Spanish for "little armored thing"), a subtropical animal with a hard shell, can be used as an indicator of climate change. The nine-banded armadillo (the only species in the United States) has migrated northward from South America over a very long period of time. The first nine-banded armadillo was sighted in the United States in 1849, a migrant from Mexico into Texas, where they were sighted in the 1850s. A century ago, the armadillo's range was restricted largely to Mexico, southern Texas, and parts of deserts in Arizona and New Mexico. By late in the twentieth century, armadillos were being sighted in Oklahoma, Arkansas, and Georgia. Armadillos' range is restricted by temperature because they have little body fat and eat insects and neither hibernate nor store food. They can
survive freezes in burrows or under buildings, however. They live in small colonies and give birth in identical quadruplets (Crable, 2005, C-5).
The armadillo has been chosen as Texas' official state small mammal. During the Great Depression, they were known as "Hoover Hogs" by down-on-their luck Americans who had to eat them instead of the "chicken in every pot" Herbert Hoover had promised as president (Suhr, 2006). The Houston Chronicle remarked in 2006 that the armadillo "has become a Yankee." "During periods of warm winters, they'll disperse north during the summers and won't die off in the winter, so the next summer, they'll disperse a little further," said Duane Schlitter, program leader for nongame species and rare and endangered species at the Texas Parks and Wildlife Department (Kever, 2006, 1).
Armadillos' accustomed range expanded rapidly as temperatures warmed after 1990, as motorists reported colliding with the animals (which seem to have very little street sense) as far north as southern North Carolina, Kentucky, Illinois, and near Lincoln, Nebraska, where one was reported during August 2005, licking up bugs on U.S. Route 50. "Over the last seven or eight years, we've been getting more regular reports of armadillos," said Mike Fritz, a natural heritage zoologist with the Nebraska Game and Parks Commission (Laukaitis, 2005, A-1).
The nine-banded armadillo is expanding its range 10 times faster than the average rate expected for a mammal, according to Dr. Joshua Nixon, a Michigan State researcher who runs a Web site, "Armadillo Online!" (www.msu.edu/~nixonjos/armadillo). Contrary to popular assumptions, the nine-banded armadillo cannot roll into a ball when threatened, but they are good swimmers, able to ford rivers by puffing air into their lungs and forging ahead, dog-paddle style. They have been discovered riding hobo-style on freight trains.
Jackson County animal control chief Lloyd Nelson said in 2006 that he had logged 13 sightings since 2003 in his Southern Illinois county alone. "All the evidence, the sightings and the number of road kills would indicate that their numbers are increasing," said Clay Nielsen, a wildlife ecologist at Southern Illinois University in Carbondale. In Illinois in recent years, "there's been quite a spurt in sightings" of the nocturnal animal. A few have been sighted in the southern suburbs of Chicago. Some may be released by people who tired of having them as pets, but others seem to have migrated northward themselves (Suhr, 2006). --
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