Effects of Climate Variability on Agroecosystems: Potential Threats to National Security

Agroecosystems are vulnerable to climate-driven perturbations and trends particularly shifts in temperature and precipitation patterns. These shifts impact soil function and the potential to sequester carbon, an important factor in agronomic productivity. In the US, about 50% of total land area is managed for efficient food production and grazing. In some regions, shifting precipitation patterns may increase rates of soil degradation and erosion resulting in negative impacts including reduced water-holding capacity and infiltration and increased flooding risk. In other regions, climate-driven storms and storm surges result in flooding and increased erosion from runoff. Increased storm surges on Pacific island territories have increased soil salinity limiting agricultural production. Drought also limits plant productivity and carbon input and increases risk of wind erosion. Even short-term droughts are major challenges to successful agriculture if soils are highly weathered, nutrient-depleted, or low in organic matter. Droughts in the US Great Plains (2011-2012) and in California (2011-2016) resulted in the loss of farmland, grazingland, and animals and price increases for food and forage. Reduced snowpack severely limits water storage and availability during the growing season for much of the US west of the Mississippi River. The Coupled Model Intercomparison Project Phase 5 (CMIP5), an international framework for couple ocean-atmospheric GCMs shows an overall future increase in US erosivity. US southwest and central Plains regions are likely to experience more severe and extended droughts. If climate-driven shifts become significant or combine with other deteriorating environmental conditions, a tipping point is reached and US agroecosystems may become unsustainable. National security could be at risk if the US loses its dominance in food production and its food supply becomes dependent on imports. Advances in modern breeding approaches and the use of novel genes from wild crop relatives as well as adjusting management strategies to mitigate risk and modifying inputs for agronomic production are only a few adaptive technological developments needed to prepare for these threats.