Invasive species don’t always spell disaster for native ecosystems and animal life, scientists say after a study of the process and its effects on New Zealand. More than 22,000 non-native plants have been introduced to the islands, the New York Times reports, and only three native species have been driven to extinction. “I hate the ‘exotics are evil’ bit, because it’s so unscientific,” one researcher says.
The study argues that the net impact of invaders is almost always positive, increasing diversity and spurring evolution. In fact, a third of today’s plants budded from natural hybridization. But critics say human-driven invasions are different: They are occurring at unprecedented rates, and with each transplant, threaten to “change the rules of existence.”