Laurence, J.A. and C.P. Andersen, 2003. Ozone and Natural Systems: Understanding exposure, response, and risk. Invited manuscript, Environ. International 29:155-160. WED-01-089
Research aimed at understanding the response of plants to ozone has been conducted for over four decades but little of it has addressed intact natural systems. Even so, there is sufficient information at this time to establish air quality standards that will protect natural terrestrial ecosystems from ozone, although that standard would be stricter than our society is currently willing to accept. What is unknown is the risk associated with continued exposure of natural systems, including both above- and below-ground components, in combination with other stresses including changing temperature and precipitation, elevated carbon dioxide, pests and pathogens, invasive species, and other activities that may fragment the landscape. Research to support an assessment of the ecological risk associated with ozone as it exists, in a milieu of stresses, must include endpoints beyond those addressed in the past, primarily productivity and species composition. To estimate the risk to society of ozone impacts on natural systems endpoints such as the integrity of soil food webs, the quantity and quality of water supplied from terrestrial ecosystems, and the transfer and fate of carbon, nutrients, and water within the systems must be quantified. Not only will this research provide the basis for a sound estimate of risk, but it will improve our understanding of fundamental ecosystem processes.