Usually, the introduction of an alien species into a habitat throws the ecosystem terribly out of balance. Far too often, invasive species even manage to drive local species into extinction.

In Hawaii, though, two alien bird species are actually helping prevent the extinction of some native shrubbery. How so, you ask? Well, after several native bird species were driven to extinction (irony, anyone?), many species of Hawaiian rainforest shrubs lost their main source of propagation. The now-extinct birds used to eat the fruit from the shrubs, then spread their seeds around the islands in "the usual way," according to a report from DailyIndia. Anyway, no birds equals no spreading of seeds, which then equals shrubbery at risk of extinction.

But a new study reveals that two alien species are helping to reverse that trend. The birds — the Japanese white-eye and red-billed leiothrix —love the fruit of six of these shrubs, dine on them "extensively," and are helping to disperse the seeds and save the native shrubs from dying out.

The weird/ironic thing is, invasive insects, plants, snakes and other reptiles, rats, cats and dozens of other alien species have already done terrible damage to Hawaii — more so than in just about any other spot on the planet. According to the state's Department of Land and Natural Resources, Hawaii "has suffered the highest rates of extinction of any area of the United States and one of the highest rates anywhere in the world, with hundreds or possibly thousands of unique species already extinct."

With that in mind, it's nice to see at least two species fitting in to do some good. But is it enough? The authors of the recent study conclude that "aggressive control of patches of non-native plants within otherwise native-dominated forests may be an important and effective conservation strategy."

Hawaii has a long way to go to save its native species. But at least it isn't all bad news.

Story by John Platt. This article originally appeared in "Plenty" in October 2007.

Copyright Environ Press 2007