The study also found that the effects of urbanization on the biological community vary geographically depending on the predominant land cover and the health of the community prior to urban development. In the study, the greatest loss of sensitive species occurred in Boston, Portland, Salt Lake City, Birmingham, Atlanta, and Raleigh metropolitan areas, where the predominant land cover was forested prior to urban development. The smallest loss of sensitive species occurred in Denver, Dallas, and Milwaukee metropolitan areas where land cover was primarily agriculture before urban development.
"The reason for this difference was not because biological communities in the Denver, Dallas, and Milwaukee areas are more resilient to stressors from urban development, but because the biological communities had already lost sensitive species to stressors from pre-urban agricultural land use activities," said McMahon.
Although urban development creates multiple stressors, such as an increase in concentrations of insecticides, chlorides, and nutrients, that can degrade stream healthno single factor was universally important in explaining the effects of urban development on stream ecosystems. The USGS developed an innovative modeling tool to predict how different combinations of urban-related stressors affect stream health. This tool, initially developed for the New England area, can provide insights on how watershed management actions to improve one or more of these stressors may increase the likelihood of obtaining a desired biological condition.
|Contact: Kara Capelli|
United States Geological Survey