RESUMO
Ecological risk assessments are used by policy makers and regulatory agencies for balancing and comparing ecological risks associated with environmental hazards. An approach for regional-scale ecological risk assessment is described and demonstrated by modeling environmental risks associated with elevated ozone in a forested region. The demonstration illustrates (1) how a regional-scale risk assessment might be done, (2) the importance of spatial characteristics in considering regional-scale risk, and (3) the necessity of considering terrestrial and aquatic linkages. Generic problems often encountered when doing regional assessments, the foremost of which is the frequent lack of region-specific information and spatial data, are also highlighted. In the demonstration, two levels of elevated ozone and five different at-risk regional features are considered (forest cover, forest edge, forest interior, landscape pattern, and lake water quality). The mechanism for impacts on these features is ozone-induced stress in coniferous trees, patches of which can then be killed by bark beetle attacks. A stochastic spatial model of land-cover change is developed to evaluate the risks or probabilities of significant changes in the selected ecological features as a consequence of these ozone-triggered beetle attacks. Risk to regional water quality of lakes is evaluated by linking the land-cover output from the spatial stochastic model to an empirical water-quality model that is sensitive to land-cover changes within a lake's watershed. The risk analysis shows that those environmental features that are sensitive to the location of coniferous forest (such as forest edge) are at risk of a significant change due to ozone-induced conifer mortality even though overall coniferous forest cover is only slightly affected. The analysis also suggests a high probability of changes in regional water quality of lakes as a consequence of location-specific forest-cover change.
