Letters to Nature

Nature 408, 79-82 (2 November 2000) | doi:10.1038/35040544; Received 12 May 2000; Accepted 15 August 2000

Elevated CO2 increases productivity and invasive species success in an arid ecosystem

Stanley D. Smith1, Travis E. Huxman1,2, Stephen F. Zitzer3, Therese N. Charlet1, David C. Housman1, James S. Coleman4, Lynn K. Fenstermaker5, Jeffrey R. Seemann3 & Robert S. Nowak7

  1. Department of Biological Sciences, University of Nevada, Las Vegas, Nevada 89154-4004 , USA
  2. Department of Biochemistry, University of Nevada, Reno, Nevada 89557, USA
  3. Division of Earth and Ecosystem Sciences, Desert Research Institute, Reno, Nevada 89512 , USA
  4. Division of Earth and Ecosystem Sciences, Desert Research Institute, Las Vegas, Nevada 89119, USA
  5. Department of Environmental and Resource Sciences, University of Nevada, Reno, Nevada 89557, USA
  6. Present address: Department of Environmental, Population, and Organismal Biology, University of Colorado, Boulder , CO, 80309, USA.

Correspondence to: Stanley D. Smith1 Correspondence and requests for materials should be addressed to S.D.S. (e-mail: Email: ssmith@ccmail.nevada.edu).

Arid ecosystems, which occupy about 20% of the earth's terrestrial surface area, have been predicted to be one of the most responsive ecosystem types to elevated atmospheric CO2 and associated global climate change1, 2, 3. Here we show, using free-air CO2 enrichment (FACE) technology in an intact Mojave Desert ecosystem4, that new shoot production of a dominant perennial shrub is doubled by a 50% increase in atmospheric CO2 concentration in a high rainfall year. However, elevated CO 2 does not enhance production in a drought year. We also found that above-ground production and seed rain of an invasive annual grass increases more at elevated CO2 than in several species of native annuals. Consequently, elevated CO2 might enhance the long-term success and dominance of exotic annual grasses in the region. This shift in species composition in favour of exotic annual grasses, driven by global change, has the potential to accelerate the fire cycle, reduce biodiversity and alter ecosystem function in the deserts of western North America.