Global warming advocates say at least a million wildlife species will ultimately be lost because the plants, trees and animals won’t be able to “keep up” with the rapid pace of man-made global warming. Laying aside the fact that global temperatures are currently declining instead of warming, how could the wild species hopefully adapt to further warming?
In Australia, biologists are closely studying the noxious alien cane toad. Bufo marinus was introduced from Southeast Asia in the 1930s to eat two species of beetles that were destroying the sugarcane fields. Unfortunately, the cane toads couldn’t jump high enough to catch many of the cane beetles. Instead, the nine-pound toads have thrived on birds’ eggs, native frogs, and any handy vegetation. Poisonous to eat, they’re also taking a toll on Australia’s natural predators.
From the species-survival standpoint, the cane toads have demonstrated remarkable changes over the decades since they were introduced. In a region where the toads have been living for more than 50 years, the researchers found the toads seldom moved very far, and meandered slowly through the cane fields. But in regions newly invaded by the toads they behaved far differently.
“Cane toads are now spreading through tropical Australia about 5-fold faster than in the early years of toad invasion,” researchers report. “The current invasion-front animals achieved these high invasion speeds by rarely using the same retreat site two days in succession, by traveling further each night when they did move, and by moving along straighter paths.”
“The rapidity and magnitude of these shifts in cane toads are truly remarkable,” says the research team, “having been accomplished in only 50 generations”—about 70 years.
Cane toads are not that unusual. Biologist Chris Thomas, of Britain’s Leeds University, got famous by predicting the million-species loss in Nature in 2001. But his own reports noted that some butterflies “increased the variety of habitat types they can colonize.” That spells broader success whether the butterflies move or not. He found two species of bush crickets “increase fractions of longer-winged (dispersive) individuals in recently founded populations.” As long as the invasions succeed, evolution will select for dispersal.
Researchers in the 1990s found mudworms in the Hudson River with an amazing tolerance for cadmium—because they lived near a battery factory. “The evolution of cadmium resistance could have taken no more than 30 years,” says Jeffrey Levinton of the State University of New York-Stony Brook.
An Antarctic fish, the Pagothenia borchgrevinki, was recently found to tolerate temperatures up to 9 degrees C warmer than the near-frozen temperatures of Antarctic waters for millenia. Thus the fish could apparently survive even if the Antarctic ice cap melted. Such melting isn’t likely, given that the East Antarctic ice sheet is currently gaining 45 million tons of ice per year; it’s gotten warm enough to snow where the ice never melts. Instead it flows slowly downhill, making a “media splash” when it falls off the edge.
All over the planet, birds, butterflies, mammals and plants have been extending their ranges closer to the poles as the earth has warmed—mostly without giving up much of their previous habitat.