Some of the world's most distinctive and biologically diverse climate regions – from South America's Andes Mountains to southern and eastern Africa and the US Southwest – may be drastically altered by century's end, endangering plant and animal life there, according to a new climate-modeling report issued March 26.
The researchers built their forecast on data contained in a massive study being published in installments this year by the Intergovernmental Panel on Climate Change. An April 6 report by the IPCC, a follow-up to its first report released last month, is expected to detail how climate shifts caused by global warming are already disrupting the habitats of many species and will drive some to extinction.
While polar regions have been thought to show the earliest, most obvious signs of global warming, the tropics will face challenging changes, the new climate modeling shows. Because tropical regions are used to steady temperatures, even small changes of 3 or 4 degrees F. could have a stronger impact than, say, a 5- to 8-degree F. change farther from the equator, according to authors John Williams and John Kutzback, both at the University of Wisconsin, and Stephen Jackson at the University of Wyoming. Their findings appear in the online edition of the Proceedings of the National Academy of Sciences.
"Disappearing climates are primarily concentrated in tropical mountains and the poleward sides of continents....
"Many current species [will be] disrupted or disappear entirely."
It's possible that some species could benefit from climate change, Dr. Williams said in a story by The Associated Press. "But we can't make a prediction, because it's outside our current experience and outside the experience of these species."
Williams played down possible beneficial effects of the change, when interviewed by the Milwaukee Journal Sentinel. From "an ecological perspective, with disappearing climates, there is no real way to put a positive spin on it," he said.
The researchers concluded that if greenhouse-gas emissions keep rising at current rates as much as 39 percent of Earth's land surface could evolve new climates, especially in the tropics, as warmer temperatures spread toward the poles, reported an article in Scientific American online. Earlier studies, the article says, estimate that species such as butterflies are migrating toward the poles at a rate of about 4 miles per decade as temperatures rise.
In the same article, Professor Jackson predicted "climates that certainly are completely outside the range of modern human experience," if greenhouse-gas emissions are unabated in the future. He said:
"If [the climate of] Memphis moves to Chicago, we have a Memphis there to say what Chicago will look like. For an area where we don't have a modern analogue, there's really nothing to look at to say, this is what the environment will look like."
The climate shifts may be even more hazardous to wildlife than are first apparent, notes Britain's Guardian. Even if a compatible climate for a disrupted species exists elsewhere, it won't do a disrupted species any good unless that species can migrate quickly to the new compatible climate. A study in 2004, the newspaper says, forecasted that 15 to 37 percent of all species could become extinct by 2050, assuming global climates warm even moderately – a loss of more than 1 million species altogether.
Williams told Reuters news service that some species may become trapped in a hostile climate:
"What we've shown is these climates disappear, not just regionally, but they're disappearing from the global set of climates, and the species that live in these climates really have nowhere to go as the system changes."
While not referring directly to the new climate- modeling study, a March 27 article in The New York Times examined the effects of consistently warmer temperatures in the "sky islands," the high-altitude regions of southern Arizona. During the past decade there, winter snows are melting earlier, forest fires have become more frequent and severe, and the trees are being eaten by beetles that used to be confined to lower, warmer altitudes. Said one resident:
"Nature is confused. We used to have four seasons. Now we have two. I love this place dearly, and this is very hard for me to watch."
The American West has warmed more than anyplace in the US outside of Alaska, one climate researcher told The New York Times. Added another, Thomas Swetnam, director of the Laboratory of Tree-Ring Research at the University of Arizona in Tucson:
"The Chamber of Commerce doesn't like people like me saying things like this, but large parts of the arid Southwest are not going to be very nice places to live."