Can humans themselves be considered an invasive species?
Absolutely. Historically, perhaps evolutionarily, that’s been one of our winning traits—for better and worse. Of course, insofar as we define evolutionary success as the ability to disperse and disseminate oneself, the same could be said of any of Earth’s existing species; the species that (prior to human involvement) were most widespread and abundant are, de facto, ones that have done the best job of dispersing and colonizing new ground. Of all species, we’ve probably done a better job of invading farthest in the least amount of time—except maybe rats and cockroaches, but they travel in our wake. How well do invasion biologists understand these patterns? The trends seem difficult to measure or even detect. The chief questions among invasion biologists are big ones: How many exotic organisms are in motion at any given time, and where are they moving to? What fraction of those organisms successfully invade? How and to what extent do those invaders affect their new environments? What fra
