POTENTIAL EFFECTS OF CLIMATE-CHANGE ON FRESH-WATER ECOSYSTEMS OF THE NEW ENGLAND MID-ATLANTIC REGION/

Numerous freshwater ecosystems, dense concentrations of humans along t he eastern seaboard, extensive forests and a history of intensive land use distinguish the New England/Mid-Atlantic Region. Human population densities are forecast to increase in portions of the region at the s ame time that climate is expected to be changing. Consequently, the ef fects of humans and climatic change are likely to affect freshwater ec osystems within the region interactively. The general climate, at pres ent, is humid continental, and the region receives abundant precipitat ion. Climatic projections for a 2 x CO2 atmosphere, however, suggest w armer and drier conditions for much of this region. Annual temperature increases ranging from 3-5 degrees C are projected, with the greatest increases occurring in autumn or winter. According to a water balance model, the projected increase in temperature will result in greater r ates of evaporation and evapotranspiration. This could cause a 21 and 31% reduction in annual stream flow in the southern and northern secti ons of the region, respectively, with greatest reductions occurring in autumn and winter. The amount and duration of snow cover is also proj ected to decrease across the region, and summer convective thunderstor ms are likely to decrease in frequency but increase in intensity. The dual effects of climate change and direct anthropogenic stress will mo st likely alter hydrological and biogeochemical processes, and, hence, the floral and faunal communities of the region's freshwater ecosyste ms. For example, the projected increase in evapotranspiration and evap oration could eliminate most bog ecosystems, and increases in water te mperature may increase bioaccumulation, and possibly biomagnification, of organic and inorganic contaminants. Not all change may be adverse. For example, a decrease in runoff may reduce the intensity of ongoing estuarine eutrophication, and acidification of aquatic habitats durin g the spring snowmelt period may be ameliorated. Recommendations for f uture monitoring efforts include: (1) extending and improving data on the distribution, abundance and effect of anthropogenic stressors (non -point pollution) within the region; and (2) improving scientific know ledge regarding the contemporary distribution and abundance of aquatic species. Research recommendations include: (1) establishing a researc h centre(s) where field studies designed to understand interactions be tween freshwater ecosystems and climate change can be conducted; (2) p rojecting the future distribution, activities and direct effects of hu mans within the region; (3) developing mathematical analyses, experime ntal designs and aquatic indicators that distinguish between climatic and anthropogenic effects on aquatic systems; (4) developing and refin ing projections of climate variability such that the magnitude, freque ncy and seasonal timing of extreme events can be forecast; and (5) des cribing quantitatively the flux of materials (sediments, nutrients, me tals) from watersheds characterized by a mosaic of land uses. (C) 1997 by John Wiley & Sons, Ltd.