Warming's biggest wallop aimed at wildlife, not people

Some of Earth's coldest areas will lose the climate zones that support today's plants and animals, says a UN panel's latest report.

from the April 6, 2007 edition

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That loss is at the cold ends of the spectrum – largely toward the poles and at high altitudes in the tropics. At the same time, some 12 to 39 percent of the planet will see hotter – or what the team calls "novel" – climate zones.

How novel? The prolonged drought the US Southwest has experienced is probably not temporary, says an international team of scientists. Instead, it's likely to be a manifestation of the northward expansion of a belt of subtropical, dry climate conditions. If the team's projections are correct, the Southwest's average climate conditions will be just as dry as the drought or the Dust Bowl. The team's results appear in Friday's issue of the journal Science's online service.

Not all effects will be harmful, many experts agree. High latitudes would experience a longer growing season. And increased carbon-dioxide concentrations in the atmosphere have stimulated plant growth worldwide – at least for now.

But such effects have their limits. Researchers have found that if water and soil nutrients available to trees, shrubs, and grasses don't keep pace with rising CO2, plant growth will stall as plants get too much of a usually good thing.

Even when plants take up lots of CO2 in the spring, they throttle back in the summer if conditions heat up and dry out. Such conditions are expected to cover broad swaths of Earth's landscape. This essentially cancels the effects of the spring uptake.

There may be other, more subtle effects. Researchers at the University of New Hampshire, for example, have found that trees, which emit hydrocarbons naturally, give off more hydrocarbons as CO2 levels rise. Scientists already have shown that these hydrocarbons, when mixed with nitrogen-based gases from coal-fired power plants, can contribute smog and tiny aerosol particles to already polluted urban air. The New Hampshire group is now trying to see what impact these additional hydrocarbons may have on air quality.

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