Could invasive species’ bad reputation be undeserved? Bucking conventional wisdom, new research suggests that if exotic species aren’t predators of natives, competition by nonnative species can actually improve biodiversity. A recent study in the Proceedings of the National Academy of Sciences notes that just three of New Zealand’s 2,065 native plants have gone extinct, despite introduction of 22,000 nonnatives. “The overall pattern almost always is that there’s some net increase in diversity,” says researcher James Brown. “That seems to be because these communities of species don’t completely fill all the niches. The exotics can fit in there.” Critics point out that historical movement by invasive species pales in comparison to the estimated 7,000 species now schlepped to a new place by humans every day. “If you pour on more species, you don’t just increase the probability that one is going to arrive that’s going to have a high impact,” says researcher Anthony Riccardi. “You also get the possibility of some species that triggers a change in the rules of existence.”