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INTEGRATED ASSESSMENTS OF ANTHROPOGENIC AND NATURAL CHANGES IN CHESAPEAKE BAY WATERSHEDS
Citation:
Walker, H A. INTEGRATED ASSESSMENTS OF ANTHROPOGENIC AND NATURAL CHANGES IN CHESAPEAKE BAY WATERSHEDS. Presented at EMAP Symposium 2001 Coastal Monitoring Through Partnerships, Pensacola, FL, April 24-27, 2001.
Description:
Both natural and anthropogenic factors affect spatial and temporal patterns in ecosystem conditions. To manage environmental change and risks, distinguishing between natural variations in ecosystem conditions and anthropogenic changes becomes important. This concept is illustrated using examples from Chesapeake Bay watersheds. Our analysis of historical and long-term proxy records of moisture, streamflow, and water quality variations demonstrates that anthropogenic activities during the past century have amplified environmental risks associated with natural climate variations and extremes in the Mid-Atlantic Region. Increased nitrogen loading to watersheds has meant that nitrogen flux per unit flow has increased over the past century, contributing to coastal eutrophication and Chesapeake Bay hypoxia and anoxia. A 10% increase in precipitation over the Susquehanna watershed could translate into a 30% increase in stream flow, making it much more difficult to reduce total nitrogen fluxes from this watershed and restore environmental conditions Chesapeake Bay. Increasing water demands due to coastal urbanization have magnified the impacts of drought. The severe drought during the summer of 1999 necessitated the first ever releases of water from Jennings-Randolf and Little Seneca reservoirs specifically for the purpose of augmenting Potomac River flow. Building and development in low lying coastal areas continues, even as sea level is rising. Thus, environmental risks associated with natural wet and dry extremes of climate and anticipated climate changes are increasing. Although many uncertainties remain, a variety actions could be taken now to reduce coastal zone risks. In parallel, additional research could help reduce key scientific uncertainties.