Analysis of climate effects on agricultural systems : white paper

Species of plants and animals have specific requirements for growth, survival, and reproduction that determine their geographic distribution, abundance, and interactions with other species. This study reviewed commonly used growth indices and more recently developed weather-driven, physiologically based demographic models. The models predict that the geographic range of the different species in each climatic system would be differentially affected, and this would complicate crop production and pest management issues. The effects of climate warming would limit tree crops that require chilling to initiate flowering. For example, olive was used to show how its range would contract in the southern part of the state due to lack of chilling, and in the northern part of its range due to severe low temperatures. The range of pests such as pink bollworm on cotton would increase into formerly inhospitable areas of the San Joaquin Valley, and their damage would increase in the current range. Similar predictions would also apply for economically important pests such as olive fly, Mediterranean fruit fly and others. The range of invasive weeds weed such as yellow starthistle would also increase in a northward direction. The effects of warming climate on biological control agents are more difficult to predict, because the biological complexity of the interactions preclude generality. This study also identified two major deficiencies: (1) the need to develop physiologically based systems models of the major cropping systems to forecast the effects of climate change on crops and on the dynamics of extant and new exotic pest introductions, and (2) the need to expand weather-gathering data systems, especially the collection of solar radiation data.