Biological pollution is sweeping the planet, as global trade carries non-native "exotic" species across all boundaries, the Worldwatch Institute announced today. Bioinvasion-the spread of exotic species-has become the second greatest threat to biological diversity.

"Because it brings the intelligence of evolution to bear, bioinvasion is a kind of 'smart' pollution," said Chris Bright, author of a new book, Life Out of Bounds: Bioinvasion in a Borderless World.

"Compared to living things, chemical spills are 'dumb'-they're inert, they cannot reproduce and they tend to dissipate over time.

"But when an exotic species establishes a beachhead, it can proliferate and spread to new areas. It can also adapt-getting better and better at exploiting an area's resources and suppressing native species."

Natural boundaries like mountains, deserts, and ocean currents used to isolate one ecosystem from another. But trade, travel, and other activities are moving organisms around these boundaries, touching off invasions.

"People often know about a few really troublesome exotics in their region," said Bright. "But they tend to see them simply as accidents. What they don't seem to realize is that these invasions are part of a pattern. This is happening virtually everywhere, and the rate of invasion appears to be growing."

Exotics can now be found in most of the Earth's lake and river systems, along most coastlines, on virtually all major islands, and scattered throughout all of the continents: