Hard Times to Come For Agriculture
In the previous article, I discussed how agricultural production contributes to climate change, but what about the other way round? What future can we expect for the production of our crops?
Corn, the second most widely grown crop worldwide, destroyed by a drought.
Crop production is already suffering from major challenges that are projected to further intensify in the near future. The changing climate is shifting the growing conditions across lands, forcing growers to move north or to higher elevations, or to change to other cultivars that are more suitable for the new conditions. Croplands have to shift at the pace of these changes, or they will perish.
Heat can also directly affect yields, for instance, a mere increase of 1ºC can reduce wheat yields between around 4 and 6.5%. High temperatures can even cause total sterility of some crops whenever they occur during important stages like pollination; for instance, the pollen of rice becomes sterile at temperatures in the mid 30ºC. In addition, extreme weather events cause devastating short-term production losses, and heat events are projected to become more frequent and severe, changes in precipitation patterns and intensity are unpredictable, and hurricanes may intensify with warmer sea surface and higher sea level.
Water scarcity is another big challenge that agriculture will face in many areas. Higher temperatures increase the evapotranspiration of plants, hence increasing the need for irrigation. An increasing pressure on irrigation water would highly threaten the yields of major staple crops that depend on it, such as wheat, corn and rice.
Last, climate change may open new ecological niches for pests, weeds and diseases, and an increase and shift in their distribution may spread them through agricultural lands and livestock that had not been exposed to them previously (e.g. Fig. 1). Insects, weeds and pathogens may migrate northward, and be moved by storms to new areas. Higher [CO2] concentrations may, in addition, reduce the crops’ resistance and favor weeds’ competitive abilities, and higher temperatures can speed up the growth rates of insect pests.
Heat can also directly affect yields, for instance, a mere increase of 1ºC can reduce wheat yields between around 4 and 6.5%. High temperatures can even cause total sterility of some crops whenever they occur during important stages like pollination; for instance, the pollen of rice becomes sterile at temperatures in the mid 30ºC. In addition, extreme weather events cause devastating short-term production losses, and heat events are projected to become more frequent and severe, changes in precipitation patterns and intensity are unpredictable, and hurricanes may intensify with warmer sea surface and higher sea level.
Water scarcity is another big challenge that agriculture will face in many areas. Higher temperatures increase the evapotranspiration of plants, hence increasing the need for irrigation. An increasing pressure on irrigation water would highly threaten the yields of major staple crops that depend on it, such as wheat, corn and rice.
Last, climate change may open new ecological niches for pests, weeds and diseases, and an increase and shift in their distribution may spread them through agricultural lands and livestock that had not been exposed to them previously (e.g. Fig. 1). Insects, weeds and pathogens may migrate northward, and be moved by storms to new areas. Higher [CO2] concentrations may, in addition, reduce the crops’ resistance and favor weeds’ competitive abilities, and higher temperatures can speed up the growth rates of insect pests.
Figure 1 - (a.) Current estimated world distribution of the cotton mealybug pest insect and (b.) projected distribution for 2070 under a high CO2 scenario (Wei et al. 2017). Note the expansion and increased occurrence in Europe, Russia and North America.
Yet, while agriculture is at high risk, the effects of climate change may not all be negative. Warming temperatures may increase crop yields in some regions (mainly in cold, temperate and humid climates) by lengthening the growing periods; but only up to a certain temperature threshold, after which heat becomes harmful. And warming will also probably expand the areas that are suitable for crop production. For instance, rising temperatures may increase Russia's wheat yields and harvested area. Moreover, higher humidity in regions where precipitations increase (at moderate intensities and frequencies) may also favour yields. And lastly, higher CO2 concentrations may have a fertilization effect on some crops that may further increase their yield, but it can also reduce the protein content of cereals like wheat, the 1st global source of vegetal protein.
All in all, climate change is affecting agriculture in diverse ways, but we can expect mainly harmful events that put global food security at stake. The economic impacts will be large, and the main victims of food insecurity will be poor communities and nations, as they are less able to secure good food with rising prices, and they have less access to global food networks.
Diego Garcia-Vega - October 27th 2017
All in all, climate change is affecting agriculture in diverse ways, but we can expect mainly harmful events that put global food security at stake. The economic impacts will be large, and the main victims of food insecurity will be poor communities and nations, as they are less able to secure good food with rising prices, and they have less access to global food networks.
Diego Garcia-Vega - October 27th 2017