Plants poised at extinction's edge.

Plants Poised at Extinction's Edge

Botanists polled in a new survey predict that 680 native U.S. plants may become extinct before the year 2000, representing "clearly the most catastrophic loss of species in evolutionary time," says Donald Falk, director of the nonprofit Center for Plant Conservation, which conducted the study.

The findings highlight the increasing rate of plant extinction in the United States. While the fossil record indicates a natural extinction rate of one plant species per several hundred to 1,000 years, the rate during the last two centuries has increased to about one per year, according to Falk. The survey results, announced this week at a Smithsonian Institution news conference in Washington, D.C., "surprised even us," Falk says.

Since 1974, when the first survey to identify threatened U.S. plants was completed, scientists have considered about 3,000 of the more than 25,000 native plant species to be at some risk of extinction. But until now they had no reliable estimate of when these species are likely to vanish, Falk says. "Our purpose was to clarify the extreme end of that spectrum," Falk told SCIENCE NEWS. "We'll use these data to set priorities for conservation efforts."

Beginning in 1987, the Boston-based Center asked botanists from around the United States to predict, from a list of more than 800 rare plants or from their own knowledge, species that could be extinct within five, 10 or more years. The 89 respondents placed 253 species in the five-year and 427 in the 10-year categories.

Nearly three-fourths of the 680 imminently endangered plants grow in five states or territories -- Hawaii, California, Texas, Florida and Puerto Rico -- all biologically diverse regions undergoing rapid population growth and extensive land development. However, it is unclear how much of the species decline is natural and how much is caused by human intervention, Falk says.

Scientists have been researching some of the imminently endangered species as possible food or technological resources. For example, several (of the genus Lesquerella) contain seed oils, used as high-quality lubricants in the electronics industry. Others have large tubers and so could be edible. In addition, many are relatives of important agricultural products and could represent the only sources of material for genetic crosses or genetic engineering to breed plants for special characteristics, according to the Center's Linda McMahan.

Although the U.S. extinction problem is serious, it is small compared with species destruction in tropical rain forests. Conference panelists say the U.S. endangered plants can be rescued. Falk and McMahan suggest increased efforts by government and private groups to legally protect plants, conserve habitats, study endangered plants in these habitats, collect seeds and educate the public. The Center cultivates rare plants in its nationwide network of 19 botanical gardens.