Toxicity Bioassays for Ecological Risk Assessment in Arid and Semiarid Ecosystems

Ecological risk assessment (ERA) is a tool used to estimate adverse effects on the environment from chemical or physical stressors. ERA can evaluate historical releases or the potential impact of proposed facilities or new chemicals. This review considers ERA in the context of historical releases of chemical stressors in dry environments. Arid and semiarid ecosystems present special challenges for application of risk assessment tools. One key problem is that most toxicity bioassays have been developed for aquatic environments or mesic ecosystems. However, roughly one-third of the earth’s land area is characterized by dry conditions. In the United States, many large federal facilities are located in arid and semiarid environments. For example, a recent evaluation of ecological resources at major U.S. Department of Energy (USDOE) facilities showed that almost 90% of the land surveyed is characterized as arid and semiarid (McAllister et al. 1996). It is anticipated that ERA will be the main tool used by USDOE to make waste management and restoration decisions in these dry systems (McAllister et al. 1996).