This paper assesses the potential impacts of climate change on the mid-Atlantic coastal (MAC) region of the United States. In order of increasing uncertainty, it is projected that sea level, temperature and streamflow will increase in the MAC region in response to higher levels of atmospheric CO 2 . A case study for Delaware based on digital elevation models suggests that, by the end of the 21st century, 1.6% of its land area and 21% of its wetlands will be lost to an encroaching sea. Sea-level rise will also result in higher storm surges, causing 100 yr floods to occur 3 or 4 times more frequently by the end of the 21st century. Increased accretion in coastal wetlands, however, which may occur in response to increases in CO 2 , temperature, and streamflow, could mitigate some of the flooding effect of sea-level rise. Warming alone will result in northward displacements of some mobile estuarine species and will exacerbate the already low summer oxygen levels in mid-Atlantic estuaries because of increased oxygen demand and decreased oxygen solubility. Streamflow increases could substantially degrade water quality, with significant negative consequences for submerged aquatic vegetation and birds. Though climate change may have some positive impacts on the MAC region, such as increased coastal tourism due to warming and some ecological benefits from less-frequent harsh winters, most impacts are expected to be negative. Policies designed to minimize adverse ecological impacts of human activities on coastal ecosystems in the mid-Atlantic, such as decreases in nutrient loading of watersheds, could help mitigate some of the risks associated with future climate variability and change in this region.

The sensitivity of hydrology and water resources to climate variation and climate change is assessed for the Mid-Atlantic Region (MAR) of the United States. Observed streamflow, groundwater, and water-quality data are shown to vary in association with climate variation. Projections of future streamflow, groundwater, and water quality are made using models determined from these associations and are applied to 2 transient general circulation model (GCM) scenarios. Regional streamflow increases in one scenario, but decreases in the other; both scenarios result in changes in the seasonality of peak flows. Response of groundwater to climate change depends on the GCM scenario used. Canadian Climate Center (CCC) scenarios suggest recharge will occur earlier in the year, and that seasonal fluctuations in groundwater levels will be less extreme. Hadley Center scenarios suggest recharge will occur earlier in the medium term, but later in the long term, with seasonal fluctuations in general being more extreme. Both scenarios show that nutrient loads can be expected to increase in winter and spring because of the expected increase in streamflow. Projected decreases in streamflow and associated nutrient fluxes in July and August could ameliorate problems associated with estuarine stratification and eutrophication in late summer. These projections demonstrate that future hydrology and water resources will be influenced by climate change, but that uncertainty in accurately projecting that influence will continue until model scenarios improve.

A fuzzy decision analysis method for integrating ecological indicators was developed. This was a combination of a fuzzy ranking method and the analytic hierarchy process (AHP). The method was capable of ranking ecosystems in terms of environmental conditions and suggesting cumulative impacts across a large region. Using data on land cover, population, roads, streams, air pollution, and topography of the Mid-Atlantic region, we were able to point out areas that were in relatively poor condition and/or vulnerable to future deterioration. The method offered an easy and comprehensive way to combine the strengths of fuzzy set theory and the AHP for ecological assessment. Furthermore, the suggested method can serve as a building block for the evaluation of environmental policies.

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