The atmospheric accumulation of greenhouse gases over the next 100 years is expected to produce significant but complex alterations in regional precipitation patterns. Several scenarios have been proposed, but the actual magnitude and direction of future precipitation changes remain uncertain. One possible scenario suggests that precipitation may decrease in mid latitudes of the northern hemisphere producing drought and soil moisture defects in many areas. Forest Ecosystems in The Southeastern United Sates should prove particularly vulnerable if projected increases in potential evapotranspiration exceed summer precipitation may increase the susceptibility of tree species to damage by insect herbivores. Trees may adjust their foliar chemistry in meeting moisture related stresses. However, progressive damage by herbivores may limit the extent of any physiological or biochemical adjustments to soil moisture deficits. Further examination of these reciprocal interaction between plants and herbivores seems especially relevant considering the growing evidence supporting the important role of insect herbivores as possible regulators of forest ecosystem processes.