Human response to environmental change in the perspective of future, global climate

Human response to severe environmental stress is conceived and implemented by individuals, but must be approved by the group. These decisions are made with respect to perceived circumstances. Societies are enmeshed within adaptive systems that provide a matrix of opportunities and constraints for a wide range of potential behavioral variability. Such systems repeatedly readjust to short-term crises, e.g., droughts, but persistent and severe environmental stress may require substantial revision of adaptive strategies. The Sahel drought of 1968–1973 is an example of a brief but severe crisis, recurring along the Saharan margins perhaps once every 30 years. Closer inspection shows links between intensified intertribal warfare and ecological stress in the lower Omo Valley. The decline of the Egyptian New Kingdom during the 12th century B.C., in response to economic stagnation, sociopolitical instability, dynastic weakness, foreign pressures, and poor Nile floods over 50–70 years, represents a more complex and fundamental modification, with systemic simplification lasting 450 years. Such insights can be applied to future, global climatic change due to increasing atmospheric CO₂. Simulation and paleoclimatic experience suggest a drier climate for the North American and Soviet breadbaskets, to threaten world food supplies at a time of maximum demographic pressures and declining resources. Public perception and remedial planning should receive the attention of Quaternary scientists, in order to preempt an involuntary, global, systemic simplification.