Boreal Forests Expected To Shift Poleward
May 6, 2013

New Berkeley Lab Climate Model Predicts Poleward Shift For Boreal Forests

redOrbit Staff & Wire Reports - Your Universe Online

What will happen to the climate in various parts of the world as the effects of global warming become amplified? Researchers from the Lawrence Berkeley National Laboratory have developed a new way to predict what will occur as temperatures rise across the Earth.

The research, which was published in Sunday´s online edition of the journal Nature Geoscience, is anticipating major changes for boreal forests, which the authors refer to as one of the planet´s leading carbon sponges.

Boreal ecosystems are found at high latitude regions in Canada, Europe and Russia and consist of coniferous trees and wetlands, officials from the Berkeley Lab explained in a statement. The vegetation there stores large amounts of carbon, keeping it out of the atmosphere.

However, their model predicts that these ecosystems will likely experience a steady shift north throughout the century. As this happens, the vegetation will surrender far more of its trapped carbon than is predicted by the majority of currently-used computer simulations.

Those models suggest that boreal forests will expand towards the poles over the next few decades as the regions to their north become warmer and wetter. They predict that, as a result of those changes, the forests would store even more carbon than they currently do.

However, the new Berkeley Lab model contradicts those claims. According to their simulation, the boreal ecosystems won´t expand poleward. Rather, they will shift towards the poles, with the key difference being that as the boreal forests move northward, the lands to the south of them will in turn be overtaken by warmer, drier climates better suited for grasslands — an ecosystem which accumulates carbon at a much slower rate than the forests lose it.

“I found that the boreal ecosystems ringing the globe will be pushed north and replaced in their current location by what's currently to their south. In some places, that will be forest, but in other places it will be grassland,” explained Charles Koven, the scientist in Berkeley Lab's Earth Sciences Division that conducted the research. “Most Earth system models don't predict this, which means they overestimate the amount of carbon that high-latitude vegetation will store in the future.”

These findings are a result of a new method of tracking global warming´s impact on the planet´s climates that is based on the premise that rising temperatures will cause a location´s climate to be replaced by a similar, yet slightly warmer, climate from another nearby region. The displaced climate would then itself shift to a different location — one with a somewhat cooler climate, eventually causing all regions to become slightly warmer.

“This approach can help determine where a given climate is going to in the future, and where a given climate will come from,” according to a Berkeley Lab statement. “Koven applied this approach to 21 climate models. He used simulations that depict a middle-of-the-road climate change scenario, meaning the range of warming by the end of this century is 1.0°C to 2.6°C above a 1986 to 2005 baseline.”

“In general, he found that climates move toward the poles and up mountain slopes. In parts of South America, warmer climates march westward up the Andes. In the southern latitudes, warmer climates head south,” they added. “But the most dramatic changes occur in the higher latitudes. Here, boreal ecosystems will have to race poleward in order to keep up with their climates. They'll also be encroached by warmer climates from the south.”

Under this model, a forest near the Canadian province of Alberta would have to move 100 miles to the north in order to maintain its current climate, and the area where it is currently located would pick up a climate that previously had been located 100 miles to the south, the researchers said. However, forests are unable to adapt to this quickly, and the shifts will lead to short-term stress and a long-term shift poleward.