USGS activities in the environment theme area include studies of natural physical, chemical, and biological processes, and of the results of human actions; the goal is to provide the understanding and scientific information needed to recognize and mitigate adverse impacts and to sustain the environment. Activities include data collection, long-term assessments, ecosystem analysis, predictive modelling, and process research on the occurrence, distribution, transport, and fate of contaminants as well as the impacts of contaminants on biota.