How big is the global weed patch?

Invasive species are a major global threat to both biodiversity and agriculture and thus are a high priority for conservation science. Governments recognize this and are devoting increasing resources toward solving the problem. Even so, there is inadequate information on where invasives occur and thus where society can best use these resources. Disturbed areas tend to be very favorable to invasives, especially the weedy species. We map the world's disturbed areas, the global weed patch, using maps of original and current landcover. At least 29.4 million km(2) (ca. 23%) of the world's ice-free land area is disturbed and thus favorable for invasive species. This weed patch map corresponds well to known locations of some of the world's worst weeds, lending support to our approach. Our results should help in setting geographic priorities for actions against invasive species.