Paleoclimate shocks: environmental variability, human vulnerability, and societal adaptation during the last millennium in the Greater Mekong Basin

Hydroclimatic variability, more so than increasing temperature, is the aspect of climate change that is most likely to directly influence the structure and function of human societies. It is also a potential source of future transboundary conflict, particularly in regions where increasing aridity is predicted under future change scenarios (Meehl et al., 2007). Increasing severity of drought and flooding, and large changes in the streamflow dynamics and the quality of fresh water supply of major waterways are of greatest concern. In order to prepare for the consequences of projected climate change and better understand the human consequences of past hydrological anomalies, it would be advantageous to have a generalized, theoretical, quantitative, and applicable understanding of how and under what conditions societies adapt to, and cope with, systematic fluctuations in water availability over a range of time scales associated with climate variability. At the same time, understanding the conditions under which societies have failed to adapt in the face of climatic shifts can further inform our understanding of the types of vulnerabilities humans may face in the future, and how well the theoretical basis for studying the human dimensions of climatic change applies to longer-term (multidecadal to millennial) scenarios. As Fagen (2004) finds, human survival in the face of major climatic shifts is commonly a function of scale. However, theoretical understanding and modeling of human adaptation to climate change is currently limited to modern welldocumented events, often over only the most recent decades, potentially limiting both the range of possible observed coupled human-environmental scenarios and the potential long-term and low frequency behavior of these coupled systems. Here we propose to extend empirical evidence of the types of hydroclimatic events that have led to societal vulnerabilities, as well as our historical knowledge of the varied adaptive strategies of affected societies. We then use these new datasets to empirically model the conditions that facilitate human adaptation or maladaption, which can advance theoretical understanding of the interaction of human systems with climate variability at a range of temporal and spatial scales.