Climate change potientially could help grow more food

Theoretically, additional CO2 in the atmosphere should help fuel crop growth. However, global warming’s other impacts could reduce crop yields. A new study in the journal Nature Climate Change by researchers in 6 countries finds the answer depends on where you live. The study has attempted to predict the combined effect of a variety of changing factors caused by climate change looking at how increased temperatures and CO2 combined with other meteorological effects might affect how efficiently food crops use water and grow. The study confirmed that severe changes from heat and water stress will harm yields. However, when CO2 is accounted for the scientists found yields of rain fed wheat could increase by 10%, while irrigated wheat, the bulk of India and China’s production, could decline by 4% and Maize decreasing by 8.5% almost everywhere. Rice and soybean flourishing in some areas and falter in others. Based on the current biomass all food crops have the potential to use water more efficiently in the future, notably by 2080. 

Bringing drought and increased temperatures, climate change has been widely portrayed as a force that will leave staple food crops struggling in many areas where they are grown today.

But a new study has shown that increasing levels of carbon dioxide in the atmosphere may actually lead to greater yields of key crops like wheat, rice and soybeans.

Scientists say higher levels of carbon dioxide in the air helps plants build up greater biomass but can also reduce the amount of water needed to help them grow.

It is difficult to predict how the mixture of factors caused by global warming will impact the way crops grow around the world, but a new study shows the increase in carbon dioxide in the atmosphere might help crops grow more in some parts, in spite of the changing climate

While the effects of a complex changing climate makes it difficult to predict exactly how crops in different parts of the world will grow, overall rising carbon dioxide levels could be beneficial.

Average levels of carbon dioxide in the atmosphere have risen by more than a quarter since 1960, and now sit at around 400 parts per million.

Plants take in carbon to build their tissues through photosynthesis, and if there is more carbon around, the process is easier.

WHY PLANTS LIKE CARBON DIOXIDE Plants take in carbon to build their tissues through photosynthesis, and if there is more carbon around, the process is easier. Leaves take in air through tiny openings called stomata, but in the process the stomata lose water. When more carbon is available, they don't have to open up as much, and this saves water.

Until now most research looking into climate change has focussed on changes in temperature and rainfall.

Many studies indicate that as temperatures rise, crops across the world will suffer as average temperatures become unsuitable for traditionally grown crops, and droughts, heat waves or extreme bouts of precipitation become more common.

But a large team of researchers have tried to predict the combined effect of a variety of changing factors caused by climate change to take into account the increase in carbon dioxide.

They introduced artificially heightened levels of carbon dioxide to farm fields, and measured the results on crop production.

Although the results are complicated, their research suggests some crops might grow better in 2080.

Researchers have introduced artificially heightened levels of carbon dioxide to farm fields, and measured the results on the production of maize, soybeans, wheat and rice. Here, experimental plots at the University of Arizona's Maricopa Agricultural Centre

The study looked at how rising temperatures and carbon dioxide along with changes in rainfall and cloud cover might combine to affect how efficiently maize, soybeans, wheat, and rice can use water and grow.

WHAT THE STUDY SUGGESTS The researchers looked at how rising temperatures and carbon dioxide along with changes in rainfall and cloud cover might combine to affect how efficiently maize, soybeans, wheat, and rice can use water and grow. The results confirmed heat and water stress alone will damage yields, but when carbon dioxide is accounted for, all four crops will use water more efficiently by 2080. Based on the current biomass of these crops, the researchers predict water-use efficiency will rise an average of 27 per cent in wheat, 18 per cent in soybeans, 13 per cent in maize, and 10 per cent in rice. This does not mean more of them will grow, however. Taking it all into account, the study projects that average yields of current rain-fed wheat areas, mostly located in higher latitudes including the US, Canada and Europe, might go up by almost 10 per cent, while consumption of water would go down a corresponding amount. But average yields of irrigated wheat, which account for much of India and China's production, could decline by 4 per cent. Maize, according to the new projections, would still be a loser most everywhere, even with higher water efficiency yields would go down about 8.5 per cent.

It confirmed heat and water stress alone will damage yields, but when carbon dioxide is accounted for, all four crops will use water more efficiently by 2080.

Based on the current biomass of these crops, the researchers predict water-use efficiency will rise an average of 27 per cent in wheat, 18 per cent in soybeans, 13 per cent in maize, and 10 per cent in rice.

'To adapt adequately, we need to understand all the factors involved,' said lead author Delphine Deryng, an environmental scientist at Columbia University's Centre for Climate Systems Research, the NASA Goddard Institute for Space Studies and the University of Chicago's Computation Institute.

She said the study should not be interpreted to mean that increasing carbon dioxide is a good thing, but its direct effects must be included in any calculation of what the future holds.

Taking it all into account, the study projects that average yields of current rain-fed wheat areas, mostly located in higher latitudes including the US, Canada and Europe, might go up by almost 10 per cent, while consumption of water would go down a corresponding amount.

But average yields of irrigated wheat, which account for much of India and China's production, could decline by four per cent.

Maize, according to the new projections, would still be a loser most everywhere, even with higher water efficiency yields would go down about 8.5 per cent.

Agricultural scientists say losses could be mitigated to some extent by switching crops or developing varieties adapted to the new conditions.

Average yields of current rain-fed wheat areas, mostly located in higher latitudes including the US, Canada and Europe, might go up by almost 10 per cent, and consumption of water would go down a corresponding amount. Average yields of irrigated wheat, much of India and China's production, could decline by 4 per cent

But the researchers warned the uncertainties in the models are high, because field experiments, which involve blowing carbon dioxide over large farm fields for entire growing seasons, have only been done at a handful of sites.

The study is less conclusive on the overall effects on rice and soybean yields - half of the projections show an increase in yield and half a net decline.

Bruce Kimball, a retired researcher with the US Department of Agriculture who has studied crop-carbon dioxide interactions, said the paper does 'a good job on a huge scale,' but 'more data from more crops from more locations' is needed.

He also cautioned that previous research has shown that the benefits of higher carbon dioxide levels tend to bottom out after a certain point, but that the damage done by heat only gets worse as temperatures mount.