University of Michigan researchers say when scientists study habitats alien species have invaded, they usually find predictable patterns: the diversity of native species declines and changes occur in natural processes such as nutrient cycling, wildfire frequency and the movement of water through the system.

Now graduate student Emily Farrer and Ecology Professor Deborah Goldberg report finding invasive species often alter the environment in ways that are beneficial to them.

"When you have an invasion, you typically see three things happening at once: the invasion, the change in environment and the decrease in diversity," said Farrer. "But they're all happening concurrently, so you can't really tell which is causing the other."

She noted additional factors might also be involved.

"For example, human activity, such as the use of fertilizers and road salt ... also may result in environmental changes that affect species diversity," Farrer added.

Farrer and Goldberg presented their research Wednesday in Memphis, Tenn., during a meeting of the Ecological Society of America.