February 1, 2005
St. Paul, Minn. — The 1200 scientists and others at the international meeting sponsored by the government of France issued a statement at the end of the 5-day-long event. It said in part, "Biodiversity is being irreversibly destroyed by human activities at an unprecedented rate. . . (demanding) urgent and significant action."
New plant and animal species are emerging, University of Minnesota ecology professor David Tilman says, but not nearly fast enough to make up for the toll caused by human activity.
"That's sort of a 1 million to 4 million year process, and yet we are causing species to be lost at rates of 100 to 1000 times faster," he says.
Tilman says the rate of extinction is approaching what scientists assume happened 65 million years ago. That's when many believe a giant meteorite struck the earth, causing a dramatic climate change that led to mass extinction.
"Thirty million years (later) things were pretty much back to normal, different species, dinosaurs were gone, mammals were here," he says.
Unlike then, Tilman argues, we can't count on time to heal the earth's wounds.
Scientists estimate there are 10 to 30 million plant and animal species on the planet, most of them unidentified. Each year as many as 50,000 species disappear. Most die off, Tilman says, because of human activity. "We take natural habitats convert them to agriculture, to suburbia, to roads, to monoculture forestry. We fish the oceans so heavily we literally have these trolling nets that scrape the bottom of the ocean clean," he says.
Dave Tilman is a member of the National Academy of Sciences, the country's top scientific body, the author of four books and more than 140 scientific papers.
Unlike some scientists, he doesn't hesitate to give his opinion on what his research means. Tilman says human behavior is affecting the environment and that our treatment of the earth amounts to a form of theft.
"What that means morally is that future generations will have a lower quality of life because we overexploited the habitat now," he says.
Tilman cites meat production as one of our most wasteful practices. He says raising grain as feed for beef cattle requires vast amounts of land and uses up lots of petroleum to make fertilizer to raise the crops.
"We're using an organism, cattle, that are highly specialized on living on low quality food, and we're giving them high quality food which their guts aren't able to handle very effectively," he says.
A wiser practice which preserves biodiversity, Tilman argues, is raising cattle on grassland that resembles the prairie. Ten years of research by Tilman and others at the Cedar Creek Natural History Area 30 miles north of the Twin Cities shows pasture with plant variety is more productive, releases cleaner water and tolerates extreme weather better.
Tilman argues saving the planet's biodiversity will require modifying human preferences for driving bigger vehicles, eating more meat and generally consuming more of everything around us.
He says we can't count on the market place alone to send the right signals for preserving biodiversity.
He says the next phase of his research will attempt to show ways for finding a balance.
"Might we be able to not only produce more pulp in a more diverse forest for paper production but maybe have that forest provide other services, cleaner water, store more carbon so we can remove more carbon dioxide from the atmosphere, helping get rid of some of our effects of burning fossil fuel. . . finding ways we can use biological diversity as a tool to help society have a more sustainable world?" he asks.
Two specific proposals emerged at the Paris meeting he attended. One is a 25-year-long effort to catalog all of the earth's species, and another is to spend $25 billion to save the 25 most threatened environments including the Amazon forest.