"I think what's really eye-opening is the depth and breadth of the impacts and consequences going on right now," said Tony Janetos, a study author and director of the Joint Global Change Research Institute at the University of Maryland.
Scientists produced the report by analyzing research from more than 1,000 publications, rather than conducting new research. It's part of a federal assessment of global warming for the U.S. Climate Change Science Program, sponsored by 13 federal agencies, led by the Department of Agriculture.
"Just to see it all there like that and to realize the impacts are pervasive right now is a little bit scary," said Peter Backlund, director of research relations at the National Center for Atmospheric Research in Boulder.
Drought-strained forests in the West and Southeast are easy prey for tree-killing insects like bark beetles. Snow in the Western mountains is melting earlier, making it more difficult for managers overseeing a long-established system of reservoirs and irrigation ditches that serves Western states.
The Southeast doesn't have the same kind of storage system because rain historically has been more consistent. Current weather disruptions have the region struggling with drought, Janetos said. Rising carbon dioxide levels are changing the metabolism of grasses and shrubs on range land, decreasing the protein levels in plants eaten by cattle.
Warmer, drier weather is altering the biodiversity of deserts in the Southwest and the high, colder deserts of Nevada, Utah and eastern Washington, said Steve Archer of the University of Arizona. Plants and animals already living in extreme conditions face threats from wildfires and nonnative species, he said.
"These areas historically support a large ranching industry, wildlife habitat," Archer said. "They are major watersheds and airsheds."
The scientists said longer growing seasons provided by higher temperatures don't necessarily translate into bigger crop yields because plants have certain growth patterns.
Their report focuses on the next 25 to 50 years, rather than the next 100 years as other studies have done.
"Sometimes it's so far out that people just don't grasp that it's a problem. This really brings it home," said Jerry Hatfield, lab director of the National Soil Tilth laboratory in Ames, Iowa.
The report makes no recommendations. Hatfield said it could help farmers consider planting new crop varieties or varying when they plant to accommodate seasonal changes.
