04-23-2003 - Biodiversity

sagar: Author=’Jorge Salazar’ program=’3761′ video=”Milford Sound, New Zealand. Photo by Dov Sax._DB:_ This is Earth and Sky. Scientists believe the total variety of life on planet Earth has been shrinking at an alarming rate.

_JB:_ It’s possible that over 11 thousand species of plants and animals are in danger of extinction today. And some of the most severe losses are on islands in the world’s oceans.

_DB:_ Yet, at the same time, more non-native species are becoming naturalized on islands. Dov Sax is an ecologist at the University of California in Santa Barbara. He and his colleagues studied extinctions and introductions of land birds and plants on over a dozen islands. They used historical and fossil records to determine that, on these islands, the number of bird species lost is roughly equal to the number that’s arrived to stay.

_JB:_ So the total number of bird species on the islands has remained constant. In contrast, because there’ve been few plant extinctions and many plant naturalizations, the number of plant species has actually doubled. Overall, biodiversity – on some islands – is increasing.

_Dov Sax:_ So this work presents a situation that really demands attention. And, I think that’s often the way science works. You answer one question and discover a hundred more.

_DB:_ More tomorrow. Thanks today to the “U.S. Forest Service”:http://www.fs.fed.us/ and the “National Fish and Wildlife Foundation”:http://www.nfwf.org/ – supporting the conservation of native fish, wildlife, plants and their habitats. We’re Block and Byrd for Earth and Sky.

Written by EarthSky