| The Valley of Oaxaca, a semi-arid region in the central highlands of southern Mexico, provides a case study through which to develop a methodology for climate change impact assessment. In this framework, both the causes and impacts of climate change originate in dialectic processes within a nexus of inter-dependent social, technical, environmental, cultural and academic production relations.;Agriculture is the most important economic activity in the Valley, and rain-fed maize the most important crop. Harvest failures from droughts occur one year in four. Annual rainfall varies with large-scale convection of water vapor transported from the Pacific and Gulf of Mexico during summer, upper-air disturbances caused by hurricanes and El Ninos. Variations in maize yields and losses have roughly equal impacts on total production. The crop is most sensitive to moisture availability during August. Yields and losses can be predicted using precipitation during this time, or directly from atmospheric circulation.;Contemporary agriculture in the Valley of Oaxaca has both traditional and modern sectors, of which both may appear within individual communities and households. The traditional sector consists of semi-autonomous rural communities using traditional technology for subsistence farming. The modern sector uses tractors, irrigation pumps, agricultural chemicals and hybrid seeds to produce cash crops and dairy products, primarily for urban consumption.;The evidence for climate change in the Valley is ambiguous and contradictory. Under either wet or dry scenarios, climate change affects the rate and pathway of the absorption of Oaxaca's traditional rural communities into the wage labor market of the larger capitalist system. Increased moisture availability would raise land productivity, promoting cash cropping and the further development of the modern market-oriented agricultural sector and leading to land consolidation and rural-to-urban migration. Decreased moisture availability, on the other hand, would inhibit cash-cropping but also lead to rural-to-urban migration due to decreased land productivity. The Valley's future will depend as much on the socio-economic and technological changes occurring there as on environmental changes. In any event, such processes are interrelated and cannot meaningfully be considered separately. |
