How do you predict that global warming will impact global food production in the future?
In California, we have a diverse climate that has traditionally allowed for the production of a wide range of foods. In fact, California is responsible for producing 95% of most of the nations's fresh produce. Production of warm season items such as tomatoes can continue most of the winter in the Imperial Valley near the Mexican border, while cool-weather strawberries are produced year-round on the foggy central coastline.
Much of the agriculture in our state relies on our predominately Mediterranean climate of cool, wet winters and hot, dry summers. Reservoirs store winter rain and snow, allowing for irrigation during the 6-7 dry months of the year. Climate predictions suggest a change in both the amount and type of precipitation - decreased amounts of precipitation, with less snow accumulation as a result of warmer average winter temperatures.
Other impacts of warmer temperatures are huge for agriculture. All fruits, including olives, need a certain amount of chill exposure in winter to initiate fruit production the next season. Fruit varieties tend to be selected by the number of chill hours appropriate for a region. Warmer winter temperatures of even a few degrees could result in too few chill hours, resulting in huge economic losses for entire regions as they are forced to replant with varieties which require fewer chill hours.
Warmer temperatures have many other impacts as well. Most insects respond to warmth accumulation, or degree days to initiate their life cycles for the season, while plants respond to either day length cues or warmth, or a combination of the two, and most birds respond strictly to day length cues. As temperatures climb, trees come into flower early, insects are productive longer, and their avian predators are out of sync, leaving harmful insect pests unchecked. Insect pollinators are also increasingly out of sync, leaving flowers unpollinated.
Some of the apparent boons of a warming climate in California mean a longer growing season, increased weed stimulation, increased insect pests and elevated CO2 levels. However, this all translates into increased water usage, at a time when we have less water to use.