Agro-meteorology Glossary

Abstract

The factors, which determine the availability of agricultural products at the local level (farm, village), are environmental conditions and management. The environment includes biophysical factors (climate, soil, pests, land available…), while management encompasses the decisions taken by farmers themselves. Management decisions are determined by the knowledge of the interactions between the environment, the characteristics of crops and animals, technology, economic factors and the institutional context (including customs, government rules, etc). By definition, economic factors play a relatively minor role for subsistence farmers. Among the listed factors, weather remains the largest source of variability of farm outputs, directly and indirectly (pests). Depending on the level of development, roughly 20 to 80% of the inter-annual variability of yields stems for the variability of weather. Losses due to pests, diseases and weeds are normally around 15% (Oerke et al., 1994). Post-harvest losses are also of the same order of magnitude. Extreme agrometeorological events are factors, which often are at the same time rare (low statistical frequency) and characterised by high intensities. They include for instance large pest outbreaks, fire, torrential rains, tropical cyclones etc. They can provoke massive destruction of infrastructure, crops, livestock, fishing gear, etc. and the loss of human life (Gommes, 1999a, 1999c).