Doubling the amount of carbon dioxide in the air significantly reduces the number of plant species that grow in the wild, according to a newly released study on climate change in California.

The results, published in the Proceedings of the National Academy of Sciences (PNAS), are the latest findings from the Jasper Ridge Global Change Project at Stanford University a multiyear experiment designed to demonstrate how grassland ecosystems will respond to predicted increases in temperature and precipitation caused by the continual buildup of CO2 and other greenhouse gases in the atmosphere.

Writing in the June 16 edition of PNAS Online, researchers found that exposing open grasslands to large doses of CO2 gas for three years caused a nearly 20 percent reduction in wildflower species and an eight percent decline in plant diversity overall. The addition of excess nitrogen and other predicted climate changes caused diversity to plunge even further, the study found.

"I was surprised how quickly we lost species over such a short time," said the study's lead author, Erika S. Zavaleta, a former Stanford doctoral student who recently joined the faculty at the University of California-Santa Cruz. "It only took three years in our experiment. What does that say about the impact global change will have on plant diversity in the longer term?"

Global changes

Located in the grassy foothills of Stanford's Jasper Ridge Biological Preserve, the Global Change Project relies on a system of infrared heat lamps, sprinklers and emitters to simulate four conditions that climate experts predict could exist a century from now as a result of continued fossil fuel consumption and deforestation: