Adapting agroecosystems to climate change is a major challenge confronting global food systems. Adaptive actions seek to moderate harm or exploit beneficial opportunities arising from changes in climate. This presentation will propose that we can separate agricultural adaptation to climate change into two different modes: adaptive migration and in situ adaptation (i.e. changes in on-farm management). We compare these modes of adaptation using two case studies. The first examines adaptive migration of rainfed crops across the globe using high-resolution crop harvested area data, irrigation data, and climate data across the last 40 years. We utilize quantile regression of temperatures to examine trends in extreme temperature exposure with and without historical migration. The second case study examines in situ adaptations in US dairy systems over a similar time period. We use milk yield and cow population data from the USDA and historical daily weather data to analyze shifts in the sensitivity of dairy yields to temperature and humidity across space and time.
These case studies establish evidence for both adaptive migration and in situ adaptations. For rainfed croplands, we find that although average growing season temperatures over areas under cultivation have increased by 0.7–1.1°C, there has been less or no increase (-1.6–0.5°C) in the upper bound (95th percentile) of temperatures experienced by maize, wheat, and rice crops because crop areas have shifted over time. For dairy systems, we find that milk yields are compromised by exposure to both extreme heat and cold, causing average daily yield decreases of around 6.4% and 4.0%, respectively. Colder regions are more sensitive to heat extremes, and warm regions are more sensitive to cold extremes, indicating that management is adapted to local conditions. Further, sensitivity to temperature and humidity has reduced dramatically over time, indicative of substantial in situ changes in infrastructure and management. Our findings suggest that both modes of agricultural adaptation – adaptive migration and in situ adaptations – are important to consider when assessing the damages of climate change.