Home Introduction Climate Variability Impacts on Ecosys. >Degradation & Restoration in Chesapeake Bay Baseline Variability: Chesapeake Bay Chesapeake Bay WQ & Climate Variability FL Everglades: Hydro. Changes & Degradation Everglades Climate Variability & Relevance Role of Time in Restoration Planning Acknowledgements References Figures

In the Chesapeake Bay watershed, extensive agriculture, urbanization, and a rapidly growing population put large stresses on water quality of rivers, tributaries, and the bay itself (Fig. 1). Before European colonization of North America, large populations of Native Americans occupied the watershed, subsisting primarily on food obtained through foraging, hunting, and after ~1000 years ago, maize agriculture (Smith, 1989). These lifestyles had minimal impact on land cover, in contrast to significant changes made by European colonists. The clearance of up to 80% of forests, peaking in the late 19^th century (Fig. 2), increased erosion and downstream sedimentation and decreased water clarity in the bay. Even as some agricultural land became reforested, increased fertilizer use and urbanization in the late 20^th century exacerbated water quality concerns (Willard et al. 2003).

Chesapeake Bay became the target of restoration efforts in 1983 when the Chesapeake Bay Program (CBP) was formed and agreements were reached to reduce excess nutrient influx that caused algal blooms and decreased dissolved oxygen in the estuary. More recently, the Chesapeake 2000 agreement was signed by government representatives of Washington DC and each state in the watershed as a commitment to restore and sustain Chesapeake Bay and its resources. This plan aimed to define water quality criteria to protect aquatic living resources and to develop targets for total maximum daily loads (TMDLs) for nitrogen, phosphorus, and sediment to attain water quality goals.

Figure 1. The Chesapeake Bay watershed, outlined in white, covers 166,000 km2 and currently houses a population of > 16 million people. As the Nation's largest estuary, the watershed encompasses urban, agricultural, and forested areas in the Atlantic Coastal Plain, Piedmont, and Valley and Ridge Provinces. Restoration efforts to improve water quality and protect living resources are anticipated to cost more than $18 billion by the year 2010 (Chesapeake Bay Commission, 2003). [larger image]

Figure 2. Timeline of land-use activities in Chesapeake Bay watershed and Florida Everglades. Although Europeans colonized the Chesapeake Bay watershed in the early 17th century, their largest impacts began in the late 19th century, when >50% of land was cleared. In the Everglades, two phases of water management (~1900-1930 and post-1950) and a rapidly growing population significantly altered the ecosystem during the 20th century. Populations in Chesapeake Bay watershed and south Florida were calculated using census data available at the University of Virginia Historical Census Browser: http://fisher.lib.virginia.edu/collections/stats/histcensus/. [larger image]