 |
||||
|
||||
|
||||
|
|
||||||||||||||||
|
||||||||||||||||
|
HUMANSÝSPEEDÝEXTINCTION
By Sean Henahan, Access Excellence  Gainesville, Fla- (3/21/97)
When humans move in, other species become extinct at a rate 100 times
faster than when they are absent, according to recent studies conducted
in the South Pacific Islands.
Photo: The endangered koloa, or Hawaiian duck David Steadman, assistant curator at the University of Florida's Museum of Natural History spent 20 months over the past 12 years studying fossil records on more than 100 South Pacific islands. His studies show an astounding effect of human actions on island birds and other wildlife. "One way to look at this is that under natural conditions we might lose a species once every 1,000 years," Steadman said. "And after people are introduced the rate is increased to one species every 10 years, which in terms of evolution is a disaster." The same phenomenon has been reported in other Pacific regions. "I studied the Hawaiian Islands for 20 years and found basically the same thing, except perhaps more dramatically so because of the more diverse fauna," said Storrs Olson, curator at the Natural History Museum at the Smithsonian Institution in Washington, D.C. "So 100 times seems like a fair number. These ecosystems are usually pretty stable until people enter the scene." Steadman worked mainly on the Cook and Tonga islands, where he found patterns of extinction that hold true throughout the island world. "All humans have a significant impact on the environment, regardless of technology, race or culture," Steadman said. "No one can claim to live harmoniously with nature. This doesn't mean we should throw up our hands and give up, because now we have more of an obligation to be responsible." The problems predate the modern age. Even the Stone Age people who came to these islands 3,000 years ago had an effect, Steadman's work shows. They cleared land, introduced other animals into the environment and trapped native birds for food. "This can be seen through studying bones at archeological sites, identifying them and tracing the changes in fauna through time," Steadman said. "Changes in vegetation can be seen through pollen records taken from lakes. Cores of mud are taken from the lakes, and the segments are analyzed to show what pollen and seeds were present at a particular period." Before humans arrived, the islands were dominated by forest. After human activity reduced the number of birds, the forest trees declined and the vegetation became dominated by grasses, ferns and other nonwoody plants. "One important factor is that a lot of these plants depended on birds to disperse their seeds or to pollinate the flowers," Steadman said. "Once the birds became extinct, nothing was left to distribute seeds. This, along with people cutting and burning, led to the decline of the forests." This kind of research should be used to guide conservation measures, such as creating bird sanctuaries on islands where a species lived before being exterminated by humans, the researchers believe. "Knowing the natural distribution of these birds can help us understand where they may be reintroduced," said Olson. "In Hawaii, the Hawaiian goose has been reintroduced on the islands of Kauai and Maui, islands where there were large populations of the birds before humans." The species that survived on these islands had to adapt quickly to the changes humans introduced. Although human involvement directly or indirectly exterminated many animals, human intervention might help preserve some endangered species. "The biggest thing we can do to preserve a species is preserve a number of habitats and keep them in good shape," Steadman said. "Once species become endangered, we need to make changes. In the past, these early people hunted these birds, they didn't stop and the birds became extinct. Now, if we can see that a species is in a big decline, we need to study why this is and make appropriate changes or we will lose the species." Related information on the Internet
| |||||||||
|
|||||||||
|
|||||||||
Science Updates Index
