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There are many units by which to measure the impact of climate change: degrees of increasing temperature, feet of rising sea level, dollars needed to adapt to a warming world. But a group of scientists in California have put forth an intriguing new unit of measurement: kilometers per year.
Writing in a paper published in Nature, scientists describe what they call the velocity (j~_~) of climate change, or more specifically, the speed of Earth’s shifting climatic zones. As global temperature rises over the next century, the scientists argue, Earth’s habitable climatic zones will start moving too, generally away from the Equator and toward the poles. That means many species of plants and animals will also have to move in order to survive.
Until now, ecologists have mostly focused on these factors as they affect individual species, but the new paper takes a more global view. By combining temperature projections on a very fine scale with global topographic(地形学的)maps, researchers have predicted change not for specific species, but for the climatic zones they need to keep up with.
Indeed, because global temperature is rising now, ecosystems are already on the move. "Once you explain it to people, it makes intuitive(直观的) sense," says co-author David Ackerly, a University of California, Berkeley, biologist. "We know what it’s like to drive north to escape the heat. It’s concrete, rather than the abstractness of rising average temperatures."
More than intuitive, this new index could also prove very useful, especially to conservationists who work to keep species from extinction. While the average velocity of climate change may be a bit less than a half-kilometer per year worldwide, according to the paper, it can be significantly faster or slower depending on the local topography. In deserts and other flat areas, climatic zones will move faster, while hilly or mountainous terrain will slow things up. According to the velocity maps that Loarie and his colleagues put together, only 8% of the world’s national parks and other preserves will retain their current climate over the next century, compounding the problem of how to keep species from going extinct.