Sustain Our Nation's Forests and Grasslands

Global and regional plant invasion patterns

At small scales, invasions are usually related to competition between species. Photo courtesy of Katie Ashdown.

ASHEVILLE, N.C. — Qinfeng Guo, a research ecologist at the Southern Research Station Eastern Threat Center, recently led a study comparing plant invasions across regional and global scales. The results were published in Landscape Ecology.

“The introductions are changing the world’s biogeography,” said Guo. “Understanding the mechanisms behind invasion patterns is critically important.”

Invasion patterns vary depending on the scale. At finer scales, invasions are often related to competition. For example, kudzu sprawls across 227,000 acres of U.S. road edges, abandoned fields, and neglected areas. Kudzu out-competes other vegetation, eventually smothering native plants.

At broader scales – such as the southeastern U.S., or the state of Alabama – invasions are usually related to humans. Human travel, trade, and other activity can inadvertently spread plants to new areas. “Many species are overcoming natural dispersal barriers at unprecedented rates,” says Guo. “The result is increased homogenization of the earth’s biotas.”

“At the global scale, no species are exotic,” says Guo. “All species are native to the planet.” When very large areas are considered, the number of exotic species shrinks. The opposite is also true – small areas have much larger exotic pools.

The study also showed that in areas with shared borders, human population density drives invasion patterns.