By WILLIAM McCALL
.c The Associated Press
It takes about 10 million years after a plant or animal becomes extinct
before anything resembling it reappears, according to a sobering study
in today's journal Nature.
``When we got that result, I was just stunned,'' said James Kirchner, a geologist at the University of California at Berkeley who conducted the analysis with Duke University biologist Anne Weil.
Biologists estimate that up to half of the known animal and plant species in the world could be wiped out within a century. Kirchner and Weil said their analysis confirms the fears of many scientists worried about the increasing loss of plant and animal life.
``It's not just, `Stop the extinction!' and things bounce back immediately. Rather, the recoveries required the fabric of the ecosystem to be rebuilt, and it takes a long time,'' said Douglas Erwin of the National Museum of Natural History in Washington.
Stanford University biologist Paul Ehrlich, author of the 1968 best seller ``The Population Bomb,'' said the research suggests the near future may be grim.
``We're going to turn into weedy world,'' he said. ``The kinds of organisms that persist are weeds, rats and insects.''
Kirchner and Weil studied a database of marine fossils to track when various species of hard-shelled animals originated and when they disappeared over the past 530 million years. Then they applied mathematical techniques developed for astrophysics.
"The passenger pigeon ain't coming back, and neither are the dinosaurs", Kirchner said.
Weil and Kirchner said their research shows that Earth may have a ``speed limit'' on the rate of recovery and that there is an underlying ``heartbeat'' to life on the planet that has some fundamental rhythm.
At the rate of recovery they calculated, they figured humans themselves could become extinct before Earth recovers.
``We spent some time debating whether this was most exciting result we found, or the most depressing,'' Weil said.
On the Net: Duke University department of biological anthropology site.