PARENT SESSION
OOS 27: From Idea to Reality: Applied Science and Ecological Problem Solving in the National Forest System.
Organized by: H Safford, R Holthausen, and T DeMeo
Thursday, August 5, 8:00 AM to 11:30 AM, Meeting Room E 143.

Critical loads for atmospheric deposition: Implications for Federal land management in the western United States.

Potter, Deborah^*,1, ¹ USDA Forest Service, Albuquerque, NM, USA

ABSTRACT- Critical loads are an important tool to protect ecosystems from atmospheric deposition, mitigate damage that could occur, or promote recovery. Consequences of exceeding critical loads can include loss of acid-neutralizing capacity, episodic or chronic acidification, nitrogen enrichment, changes in biotic communities, and toxicity. Eutrophication in high elevation aquatic ecosystems and some coastal waters can also occur. Critical loads are widely adopted by many European countries and Canada, yet the U.S. has no regulatory strategy to use critical loads to control air pollutants such as nitrogen and sulfur. Land Managers need to evaluate the effects of atmospheric deposition on ecosystems to describe baseline conditions and to predict the impact of new sources of pollution before facilities such as power plants are constructed. Federal Land Managers have been developing common approaches for incorporating critical loads into the policy and management processes, and Forest Service researchers are establishing demonstration projects for calculating critical loads. Selecting critical loads for national parks and wilderness areas is a policy decision based on sound science. Deposition effects on surface waters have been estimated by the Forest Service using the Model of Acidification of Groundwater in Catchments(MAGIC) and other models. Federal Land Managers also set target loads to provide a safety margin or intermediate recovery goals. This paper presents the status and future needs for critical loads for atmospheric deposition in U.S. federal land management.

Key words: critical loads, sulfur, atmospheric deposition, nitrogen