Climate change and environmental pollution: Physical and biological interactions

Climatic change projected over the next century may occur in an environment already affected by other stress, including UV-B enhancement, air pollution and increasing nutrient fluxes. Focusing on particular ecosystems, temperate zone forests, freshwater lakes, and estuaries, we have examined the interactions among these several environmental problems. An important chemical outcome of atmospheric change is the increase in oxidant levels throughout the lower atmosphere and the hydrosphere. These oxidants are phytotoxic and contribute directly and indirectly, along with other stresses on ecosystems, to the acceleration of the S, N and C cycles. These changes may lead to the net transfer of nutrients from land to coastal ocean with accompanying forest decline and coastal eutrophication. Some shifts already may be under way locally, but the synergistic nature of the stresses threatens to accelerate these processes over the next few decades. In addition to any direct consequences of climatic change, the aggravation of existing environmental problems is an important indirect consequence.