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In a new study by the United States Geological Survey (USGS), it was found that the loss of sensitive species in streams begins to occur at the initial stages of urban development. The culprits are the increased contaminants entering the streams, destruction of riparian habitat, and greater stream flow flashiness. The results of the study show that streams are more sensitive to development than previously believed. The victims are the bruised ecosystems and a reduction in economically viable resources like fishing and tourism.
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“We tend not to think of waterways as fragile organisms, and yet that is exactly what the results of this scientific investigation appear to be telling us,” said USGS Director Marcia McNutt. “Streams are more than water, but rather communities of interdependent aquatic life, the most sensitive of which are easily disrupted by urbanization.”
For example, the study found that once urban development approached 20 percent in watersheds in the New England area, aquatic invertebrate communities lost about 25 percent of their biodiversity.
Multiple streams in nine metropolitan areas in the continental US were sampled. The study areas included Atlanta GA; Birmingham AL; Boston MA; Dallas TX; Denver CO; Milwaukee WI; Portland OR; Raleigh NC; and Salt Lake City UT.
The USGS researchers found that the degree of change to the biological communities of streams varied geographically depending on the predominant land cover and health of the ecosystem prior to urban development.
In areas such as Boston, Portland, Salt Lake City, Birmingham, Atlanta, and Raleigh, there was a greater loss because the land cover prior to development was forest. In areas such as Denver, Dallas, and Milwaukee, there was less loss because the prior land cover was more agricultural.
“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 Dr. Gerard McMahon, lead scientist on the study.
The study found that no single stressor was universally important. The result is a combination of all stressors combined, like increased concentrations of insecticides, chlorides, and nutrients. Management strategies are used throughout the US to reduce these impacts, but unfortunately, this study shows that the effects of urbanization can be felt even at the early stages.
For more information on this and past studies, as well as graphics and maps, click here.
Charles River image via Shutterstock