February 6, 2009

Climate Change May Carry Invasive Weeds Back And Forth

Global warming is likely to result in more preferred conditions for many of the most unwanted weeds to invade the West, researchers reported on Friday.

Additionally, climate change may also allow farmers to restore native plants in some regions, said Bethany Bradley, Research Associate at Princeton and lead author of the study appearing in Global Change Biology.

While the changing climate may rid the west of many invasive plants that already reside in the region, others are expected to take their place soon thereafter.

"We're going to have to be in the right place at the right time before something else gains a foothold," Bradley and colleagues said.

Non-native plants cause millions of dollars in damage to farms and ranches in the West, according to the AP. They also can change the flow of water and cause massive wildfires to grow out of control, resulting in even greater losses of state and federal funding.

"Every county that I know of in the West has got nonnative or invasive weeds in it," said Steve Dewey at Utah State University's extension office. "My advice to county weed departments is to give new invaders high priority, to stop them before they get out of hand."

Using 10 atmospheric models predicting how the West's climate will change by 2100, Bradley constructed plant distribution models for several common invaders in the United States, including cheatgrass (Bromus tectorum), yellow starthistle (Centaurea solstitialis), leafy spurge (Euphorbia esula), kudzu (Pueraria montata), and cogongrass (Imperata cylindrica).

Researchers note that cheatgrass could struggle in conditions of higher temperatures and less water, and therefore will probably migrate from southern Nevada and Utah into places like Idaho, Montana and Wyoming.

Yellows starthistle could move into California and Nevada, while spotted knapweed moves toward higher elevations and spreads in Montana, Wyoming, Utah and Colorado, researchers said.

Researchers formed the best predictions based on the information readily available. However, some conditions, such as levels and locations of precipitation, remain uncertain.

"It's a big wildcard out there," Bradley said. "Even small changes in precipitation can have big impacts on invasive and native plants in the western U.S."

"The question for policy makers and land managers is, 'What do we want these lands to be?'" David Wilcove, one of the researchers on the study, said in a statement. "These lands will change, and we must decide now - before the window of opportunity closes - whether we do nothing or whether we intervene."

Researchers hope the atmospheric models will help them manage invasive weeds in the West in the coming decades, Dave Burch, Montana's weed coordinator and, until December, chairman of the Western Weed Coordinating Committee, told the AP.

"Prevention is the cheapest way to go with weed control," Burch said. "Once you get something here, it's usually too late."


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