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Rising temperatures are a bomb under wheat production

Wheat production will be greatly affected by climate change. New research estimates that global wheat production will decline by six percent for each one-degree rise in temperature. One of the solutions is to develop more heat-tolerant varieties.

2015.01.07 | Nina Hermansen

Wheat production will be greatly affected by climate change Photo: Janne Hansen

Global warming does not only affect ecosystems in the oceans and on land. It also has major implications for the future food production. 

A group of scientists, including Professor Jørgen E. Olesen from the Department of Agroecology at Aarhus University, document in a new study that even small changes in temperature will have a significant impact on the production of wheat. The results have just been published in the prestigious scientific journal Nature Climate Change.

The study shows that a temperature rise of one degree results in a six percent drop in global wheat production. To put it into perspective: global wheat production in 2012 amounted to 701 million tonnes; a six percent reduction is therefore 42 million tonnes. This actually corresponds to a quarter of the global trade in wheat in 2013.

- We are now much more confident that temperature increases will have an impact on wheat production. The problem is significantly larger than expected and may in some places actually be disastrous. If the temperature rises above 30 degrees, it can be very difficult to get any yield at all, says Jørgen E. Olesen.

Yields have already started declining

Wheat yields decline with rising temperatures because of several factors: One of the main problems is that higher temperatures cause the crop to mature too quickly. This makes the growth period too short. High temperatures during flowering also mean that the wheat flowers become sterile, thus producing no grain. High temperatures during grain filling can also wither the leaves responsible for the vital photosynthesis. Heat also means higher evaporation, leading to problems with water shortage.

The study on how wheat production is affected by temperature increases was based on the use of 30 wheat models. The models are mathematical tools that can calculate yields under different conditions. However, the reliability of the models under a warmer climate has been questioned. 

In order to test the models, the scientists compared model calculations with results from two specific experiments where wheat yields were measured under different temperatures. It turned out that the average results of the model calculations were very close to those of the experiments.

- We then used a combination of models to investigate how yields globally have changed over time – and from that we extrapolated to give a future scenario. It turns out that the rise in temperature is even now a problem in the places where the temperature is already high and the climate is dry. It is also here that the future drops in yield will be the largest, says Jørgen E. Olesen, pointing out that it is also important to remember that overall the temperature rise will lead to lower yields not only in wheat, but in many other cereals too. 

New varieties part of the solution

How large the problem of global warming will be for wheat production does, of course, depend on the size of the future temperature rise. 

According to Jørgen E. Olesen, we can expect a temperature rise of at least one degree over the next 30 years. This is a challenge to the current wheat varieties. Studies have shown that different varieties respond differently to high temperatures and that some genotypes are more tolerant to a future warm climate. 

- There is a large variability in the robustness of wheat varieties and herein lies one of the solutions to the problem. We simply need to look at whether it is possible to breed better varieties. It is also necessary to modify cultivation systems, particularly to improve water use efficiency. However, even with the development of more tolerant varieties and better cropping systems, there is unfortunately no way of getting around that yields will generally be lower, says Jørgen E. Olesen.


Further information 

Read the article ”Rising temperatures reduce global wheat production” in Nature Climate Change.

Professor Jørgen E. Olesen
Department of Agroecology
e-mail: jeo@agro.au.dk
Telephone: +45 8715 7778 /4082 1659

DCA, Agro, Crops