Image of the Day: Controlling Invasive Plants

Conventional wisdom says that invasive plants introduced to a foreign environment thrive because they don't have natural enemies to keep them in check, but a new study suggests that's not true.

Researchers at the Georgia Institute of Technology analyzed field studies of more than 100 exotic plant species in ecosystems ranging from deserts to lake bottoms. They found that native herbivores in invaded areas are better at controlling invasive plant species than the usual enemies of the plants. At the same time, introduced herbivores are harder on native species than on invasive ones. This can trigger an ecological "meltdown" in which one invasive species paves the way for invasions by others by not eating them in their new environment, the researcher said.

Each year, invasive exotic species cause an estimated $120 billion in damage in the United States, not to mention the untold amount of harm they do to the structure and function of native ecosystems. In this latest study, researchers found that exotic herbivores, including cattle, rabbits and goats introduced by Old World explorers, can encourage the spread of invasive exotic plants - increasing their relative abundance by nearly 70 percent over native plants.

The study is detailed in the March 10 issue of the journal Science.