“Shredded Heat” – Crop Failure and Climate Change
Future climate changes are likely to bring an increase in crop failure rates, according to a study carried out by researchers at the University of Leeds. This is a problem with global implications, “due to the importance of international trade, crop failure is an issue the affects everyone on the planet, not just those in crop-growing regions” says lead author of the study Dr. Andy Challinor. However, if we start planning now, there may be ways for farmers to adapt.
Climate scientists are working to try and better understand the environmental changes we may expect to observe in the future, and together with social scientists and economists, the impacts these will have on the human population. The latest estimates suggest that, with continued emission of greenhouse gases, global temperatures in the year 2100 will have risen by between one and six degrees Celsius; compared to the average temperature at the end of the twentieth century. The wide range of possible temperatures results from the uncertainty inherent in forecasting future energy use and population trends, in combination with trying to predict the response of the climate system using limited historical observations. A further temperature increase of even one or two degrees would have dramatic impacts on regional climates and sea level for much of the planet.
An area of particular concern for us is the effect that these climatic changes may have on future food security. Crops, like all plants, have a few basic requirements for growth: sunlight, heat, nutrients and water; too much or too little of any of these may cause trouble for farmers. Increases in temperature can shorten the time it takes for crops to reach maturity, therefore reducing the volume of crop a farmer is able to harvest. Rising temperatures also bring with them reduced water availability, further exacerbating the problem. However, gradually rising temperatures and declining water availability are not the only issues. Extreme weather events such as heat waves and drought also impact farmers and are expected to become more frequent over the next century. A heat wave occurring during a particular part of a crops reproductive cycle can drastically affect its eventual yield, while the effect of droughts on crop productivity is less clear. Droughts that would be considered minor by meteorologists can sometimes result in significant crop failure, whilst in other cases large scale droughts have left crop yields relatively unaffected. This disparity is thought to reflect different levels of socio-economic adaptation to the situation.
If the already mentioned problems weren’t enough, there is the possibility that at higher temperatures or atmospheric greenhouse gas concentrations, ecosystems may undergo unpredictable changes in productivity that we currently do not understand. But these are not only problems for future generations; the Russian government was recently forced to ban wheat exports after the country experienced its worst droughts for a century, highlighting the need to improve our understanding and ability to adapt, quickly.
In collaboration with the Met Office, researchers from the School of Earth and Environment at the University of Leeds have investigated the implications of future climate change for crop productivity, under a variety of adaptation scenarios. Predicting crop yields requires the simulation of a number of complex and interlinked physical and socio-economic processes. Therefore, models have been developed to combine both empirical physical relationships and data from past events, in order to gauge what may happen in the future. This work, recently published in Environmental Research Letters, used data on spring wheat growth in four provinces of Northeast China as a case study. The latest Met Office climate model was used to simulate a future climate, with subsequent wheat yields generated by the General Large-Area Model (GLAM) for annual crops. The results indicated that the percentage of harvests failing in this region would increase as global and local mean temperature rises; baseline crop failure approximately doubled for a temperature increase of between two and four degrees Celsius.
So, are we destined for global starvation, or can we do something to address this problem? To investigate, the researchers imposed a number of adaptation strategies upon their simulations. These strategies involved the development of crops with greater heat and drought tolerance, improved irrigation systems and socio-economic adaptation. “It is highly unlikely that we will find a single intervention that is a ‘silver bullet’ for protecting crops from failure. What we need is an approach that combines building up crop tolerance to heat and water stress with socio-economic interventions” said Challinor. By adapting to both water and heat stresses, the percentage of simulated harvests failing was brought to below the baseline value obtained from historical data; with water stress adaptation providing the greatest benefit.
The team now plan to expand their research to look at other crops in different regions and examine more closely the mechanism by which increased gross domestic product (GDP) appears to protect against drought. “It appears that more developed countries with a higher GDP tend to evolve more advanced coping mechanisms for extreme events. In China this is happening organically as the economy is growing quickly, but poorer regions such as Africa are likely to require more in the way of aid for such development” said co-author of the study Dr. Evan Fraser.