Links to Agroecosystems: Processes and Productivity

The climate teleconnections related to El Niño–Southern Oscillation (ENSO) events described in chapter 1 have global implications regarding agriculture. In many locations, ENSO events appear to account for a significant part of the climate variability that governs the responses of crops and livestock on a range of temporal and spatial scales. Teleconnections affect variations in production both within growing seasons and from one season or year to another. Precipitation, temperature, and other climate variables are key determinants of crop growth and livestock health, affecting all aspects of agroecosystems, including the survival and reproduction of both beneficial and damaging insects. An understanding of ENSO teleconnections may help farmers and regional planners assess changes in probable yield levels before the growing season and thus provide guidance for improved management. In this chapter we introduce agricultural responses to climate extremes in general and to ENSO climate teleconnections in particular. Subsequent chapters describe methods of analysis, use of ENSO predictions for agriculture, and regional aspects in more detail. Variability in agricultural production affects risk on at least five levels: individual farms, farming regions within nations, nations, groups of nations, and the global food system. Contributing factors and consequences of variability at successive levels differ in type and scale. Perhaps the most relevant example of these differences is the contrast between the effect of variability on a single farm and its effect at the national level for any country in which the agricultural sector plays a significant role in the overall economy. At the individual farm level, the aim is generally to produce high yields as consistently as possible. Hence, the main concern regarding climate is the occurrence of seasons with low yield levels that threaten subsistence or income. When regional or national yields are very low, overall food security may be threatened, necessitating relief efforts by donor countries and agencies. At the national level, however, problems may be caused not only by low yields but also by the opposite—unusually high yields. Whereas low national yields may cause food shortages and high food prices, high overall yields tend to lower commodity prices paid to farmers and create excessive surpluses that necessitate government intervention. High variability in food production at the national level thus can destabilize domestic prices, farm income, and national budgets.