Saturday, March 26, 2011

Moving with Climate Change

Scientists Chris Field and Scott Loarie
We frequently worry about the effect that climate change will have on where we live.  If it changes enough, we can move (or adjust the air conditioner).  If you are an animal with specific food needs that are climate dependent, you may move to find them.  Unfortunately, your plants can't move as fast.

Climate change is moving also across the landscape.  The temperature drops as you go up a mountain but if the climate is warming, the temperature is going up at every altitude which may be a short distance.  "In the Amazon Basin you might have to move up to ten times faster to keep pace with future changes in climate."*  If you are a plant or fungus, that move may take more time than climate change allows.

Dr. Chris Field and Scott Loarie from Stanford University have been studying climate velocity, the time that different areas require for adaptation.  Their studies show the following:
"The researchers found that as a global average, the expected temperature velocity for the 21st century is 0.42 kilometers (0.26 miles) per year. But this figure varies widely according to topography and habitat.

In areas of high topographic relief, where species can find cooler temperatures by climbing a nearby mountain, velocities are relatively low.  In flatter regions, such as deserts, grasslands, and coastal areas, species will have to travel farther to stay in their comfort zone and velocities may exceed a kilometer per year.

Can the planet's ecosystems keep up?  Plants and animals that can tolerate a wide range of temperatures may not need to move.  But for the others, survival becomes a race.  After the glaciers of the last Ice Age retreated, forests may have spread northward as quickly as a kilometer a year.  But current ecosystems are unlikely to match that feat, the researchers say.  Nearly a third of the habitats in the study have velocities projected to be higher than even the most optimistic plant migration estimates."
Dr. Fields says that you can think of climate velocity as "a kind of sprinting capacity that these plants and animals need if they're going to stay in the climate zone that they're in now."  If you want to see the velocity of climate change in a particular area, click on their Climate Velocity Tool and select an area on the map.

A bigger danger yet is habitat fragmentation.  If the change in temperature velocity is a quarter mile a year but you are a rare plant in a small isolated prairie with fescue fields on all sides, you have no way to spread into a favorable climate.  As the song said, "Whoops, there goes another rubber tree plant."


* For a more detailed explanation, download the PDF file "Making the Paper" at Stanford.edu.

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