Forest loss in one part of US can harm trees on the opposite coast

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May 15, 2018

Large swaths of U.S. forests are vulnerable to drought, forest fires and disease. Many local impacts of forest loss are well known: drier soils, stronger winds, increased erosion, loss of shade and habitat. But if a whole forest disappears, new research shows, this has ricocheting effects in the atmosphere that can affect vegetation on the other side of the country.
A University of Washington-led study published May 16 in Environmental Research Letters shows that forest die-offs in specific regions of the United States can influence plant growth in other parts of the country. The largest impacts seen were from losing forest cover in California, a region that is currently experiencing dramatic tree mortality.

This August 2016 aerial photo of the Sierra Nevada Mountains in central California shows widespread tree loss. The new study shows changes here can affect plant growth across the country.U.S. Forest Service

“These smaller areas of forest can have continental-scale impacts, and we really need to be considering this when we’re thinking about ecological changes,” said first author Abigail Swann, a UW assistant professor of atmospheric sciences and of biology.
Such far-off effects are accepted in the atmospheric sciences community, Swann said, but the idea is only beginning to be accepted by ecologists.
A 2016 study from the same UW group looked at what removing trees from larger areas, like western North America or the entire Amazon rainforest, would mean for worldwide plant growth. This study took the same approach on a regional scale.

The study divided the mainland U.S. into the 18 ecological regions shown in this map. The strongest response seen in models was for tree loss in the Pacific Southwest (PS) region, shown in light brown, which covers most of California.NEON

The project divided the mainland U.S. into the 18 regions used in the National Ecological …

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