Letters to Nature

Nature 420, 403-407 (28 November 2002) | doi:10.1038/nature01028; Received 17 April 2002; Accepted 11 July 2002

Altered performance of forest pests under atmospheres enriched by CO2 and O3

Kevin E. Percy1, Caroline S. Awmack2, Richard L. Lindroth2, Mark E. Kubiske3, Brian J. Kopper2, J. G. Isebrands4, Kurt S. Pregitzer5, George R. Hendrey6, Richard E. Dickson3, Donald R. Zak7, Elina Oksanen8, Jaak Sober5, Richard Harrington9 & David F. Karnosky5

  1. Natural Resources Canada, Canadian Forest Service-Atlantic Forestry Centre, Fredericton, New Brunswick, E3B 5P7, Canada
  2. Department of Entomology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
  3. North Central Research Station, US Forest Service, Rhinelander, Wisconsin 54501, USA
  4. E7323 Highway 54, P.O. Box 54, New London, Wisconsin 54961, USA
  5. School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, Michigan 49931, USA
  6. Brookhaven National Laboratory, 1 South Technology Street, Upton, New York 11973, USA
  7. School of Natural Resources & Environment, The University of Michigan, 430 E. University, Ann Arbor, Michigan 48109, USA
  8. Department of Ecology and Environmental Science, University of Kuopio, 70211 Kuopio, Finland
  9. Plant and Invertebrate Ecology Division, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK

Correspondence to: Kevin E. Percy1 Correspondence and requests for materials should be addressed to K.E.P. (e-mail: Email: kpercy@nrcan.gc.ca).

Human activity causes increasing background concentrations of the greenhouse gases CO2 and O3 1. Increased levels of CO2 can be found in all terrestrial ecosystems2. Damaging O3 concentrations currently occur over 29% of the world's temperate and subpolar forests but are predicted to affect fully 60% by 2100 (ref. 3). Although individual effects of CO2 and O3 on vegetation have been widely investigated, very little is known about their interaction, and long-term studies on mature trees and higher trophic levels are extremely rare4. Here we present evidence from the most widely distributed North American tree species5, Populus tremuloides, showing that CO2 and O3, singly and in combination, affected productivity, physical and chemical leaf defences and, because of changes in plant quality, insect and disease populations. Our data show that feedbacks to plant growth from changes induced by CO2 and O3 in plant quality and pest performance are likely. Assessments of global change effects on forest ecosystems must therefore consider the interacting effects of CO2 and O3 on plant performance, as well as the implications of increased pest activity.