That’s what we can expect from that kind of temperature increase. By the end of the century, it is projected that we will be experiencing summers warmer than the warmest now on record. Yields of our major temperate crops decline rather markedly above about 30 degrees centigrade for several reasons. The temperature optimum for a photosynthesis is in the range of 20 to 25 degrees and its efficiency declines above that.
In addition, development accelerates with temperature, so that there isn’t as much time to convert the photosynthate into the oils and the starches that comprise the bulk of the harvested crop. Another variable that is becoming critical is water. Today about 40 percent of the surface of the earth is dry lands, and some 35 percent of the population lives in drylands areas.
Water tables in many of these dry regions are being drawn down more rapidly than they can be renewed. So we are approaching water crises, not only from increasing competing demands from energy production, urbanization, and others, but there will be additional drying and heating in some of the most populous places on the earth.
The red circles indicate the areas that are expected to experience moderate to severe water scarcity in the future. What that means is that the shape of the future is pretty daunting. Energy, freshwater and arable land are likely to be no more abundant, if anything less abundant. What will certainly increase is demand--that is the number of people—the extent of dry lands and the temperature.
So how do we go about adapting agriculture to climate change while we continue to increase productivity and decrease environmental impact? What people are talking about today is increasing tolerance to heat, drought and salinity. That’s going on now in both biotech companies and in public breeding programs. Increasing pest resistance is important, because we’re expecting and already seeing shifts in distribution of pests and diseases. But there are also big issues such as addressing the limits on photosynthetic efficiency, which is not a major research focus at the moment. The kinds of techniques that are being used and will be used include conventional breeding and marker assisted breeding.
In the future, however, it will require some combination of even more sophisticated marker assisted breeding and molecular modification. Here’s where we are a bit stuck in the sense that although we have a regulatory apparatus, it is prohibitive. To encourage more active crop development, particularly in the public sector, the regulatory regime needs to be re-evaluated in the light of accumulated evidence on the safety of genetically modified crops.