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Streams Begin to Degrade at Earliest Stages of Urban Development

Streams Begin to Degrade at Earliest Stages of Urban Development


According to a recent study by the United States Geological Survey (USGS), sensitive species in streams can begin to disappear at the earliest stages of urban development.  The Department of Interior has long known that urban development affects stream quality and biodiversity, but the new study suggests the streams are more vulnerable than once thought. 

Urban development introduces contaminants into the stream, destroys the surrounding habitat, and increases streamflow during flash floods.  EPA regulations of wetlands and certain natural habitats as well as local codes and ordinances have restricted urban development in vulnerable areas, but significant damage is still occurring. 

For example, the USGS states that by the time 20 percent of watersheds were affected by urban development in New England, about 25 of invertebrate diversity disappeared. 

During the study by the USGS, the followed studies areas were observed: Atlanta, GA, Birmingham, AL, Boston, MA, Dallas, TX, Denver, CO, Milwaukee, WI, Portland, OR, Raleigh, NC, and Salt Lake City, UT.  The study found that areas ranging biologically and geographically responded differently to the affects from urbanization. 

For example, the areas that experienced the most loss of sensitive species were covered by forest before urban development.  These areas included the Boston, Portland, Salt Lake City, Birmingham, Atlanta, and Raleigh metropolitan areas.  Areas with the smallest loss of sensitive species were mainly covered by agricultural land before urbanization.  These areas included the Denver, Dallas, and Milwaukee metropolitan areas. 

Dr. Gerard McMahon, the lead scientist during the study, states: “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.” 

The USGS study found that degraded streams can in fact undergo improvements.  However, the improvements on stream quality and biodiversity are only possible with environmental management plans, legislative action in local areas and entire watersheds, and strict enforcement of zoning codes within metropolitan areas.

The USGS found that no stressor is directly responsible for the degradation of streams.  In other words, no insecticide, chloride, or nutrient is solely responsible for the degradation.  Identifying all stressors and their combined effects on the environment is key. 

USGS Director Marcia McNutt stated: “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.  Streams are more than water, but rather communities of interdependent aquatic life, the most sensitive of which are easily disrupted by urbanization.”

Source: United States Geological Survey