Climate change threatens corn crops

February 28, 2013 by Tom Marshall
Climate change threatens corn crops

A warming world is putting crops at risk, according to scientists who studied how the weather affects French maize yields.

If climate-change projections are right, we'll need to improve yields per acre by as much as 12 per cent between 2016 and 2035 just to maintain today's total production.

The results reveal a real threat to our food supply in the coming decades. It turns out that maize yields drop significantly for every day when temperatures climb over around 32°C, and that has been as important an influence on maize yield as variation in rainfall since the turn of the century.

Over the past 50 years, the average number of days over this dangerous threshold has already risen from around three per year to more than five, and it is predicted to grow to around ten a year over the next two decades. In some major maize-growing regions it could be as much as 15 days per year above this damaging threshold.

'It's a serious risk to food security,' says Dr Ed Hawkins of NERC's National Centre for and the University of Reading, who led the study. ' increased fourfold since the 1960s, largely due to better technology such as pesticides and , but this improvement has slowed in recent decades and the current rate of increase in technology may not be enough to maintain current production levels.' Better and new will help, but there's no guarantee we can meet the target.

The team analysed of the influence on maize yields of rainfall and over the last half-century, combining historical crop data with . They then used projections of future daily maximum temperatures to predict the effects of heat stress on yields in the future, assuming that the historical relationship between climate and yield variations continues to hold, and tested these predictions against historical data to make sure they represent the world accurately.

The findings show that extremes of temperature have gained in importance relative to variability in rainfall since the 1960s. Hawkins says this is probably because French farmers have greatly increased their use of irrigation, so that dry spells don't do so much harm to their crops. But irrigation gives no protection against extreme heat; during the 2003 heatwave, the nation's fell by around 20 per cent compared to the year before. Things may be a little different in other countries, but the basic picture is likely to be similar.

'Predicting rainfall is very difficult compared to predicting temperatures, but we think it will change much less than temperature over the next couple of decades,' says Hawkins. Climate models predict strong temperature increases over the twenty-first century with relative confidence, due to continued growth in greenhouse gas emissions, whereas rainfall changes are less certain.

The falloff in rates of yield improvement since the heady days of the so-called 'green revolution' may be partly due to the temperature rise we've already had. But it may also be because the obvious steps to boost yields with steps like breeding better seeds, greater use of machinery and heavier use of fertilisers and pesticides have already been taken, and that future improvements will be much harder to achieve. The 12 per cent figure is a worst-case scenario that includes a margin for error; if we could manage that, we could be very confident of at least maintaining current production. Hawkins says it's possible that a lower figure would be enough, provided the warming that happens is towards the lower end of expectations.

Different crops have varying tolerance for heat, but all have a threshold above which they suffer damage. Techniques like genetic modification or more efficient selective breeding may be able to help farmers develop new varieties that can handle hotter conditions, but it's not certain how far this process can go. If climate change continues unabated, farmers might need to start switching to entirely new crops that are currently grown in hotter parts of the world.

Hawkins says the group now hopes to extend the study, applying the same methods beyond France and to a wider range of crops.

The paper appears in Global Change Biology.

Explore further: Study finds growing evidence of global warming threat to future food supplies

More information: Hawkins, E., Fricker, T. E., Challinor, A. J., Ferro, C. A. T., Ho, C. K. and Osborne, T. M. (2013), Increasing influence of heat stress on French maize yields from the 1960s to the 2030s. Global Change Biology, 19: 937-947. doi: 10.1111/gcb.12069

Related Stories

Technology, economics may counter climate impact

February 24, 2011

The impacts of climate change on corn yields in the United States and China in coming decades may not be all bad, according to a new Cornell and University of Tokyo study published in a recent issue of the journal Agricultural ...

Climate-driven heat peaks may shrink wheat crops

January 29, 2012

More intense heat waves due to global warming could diminish wheat crop yields around the world through premature ageing, according to a study published Sunday in Nature Climate Change.

Recommended for you

US scientists raise bar for sea level by 2100

January 24, 2017

In the last days of Barack Obama's administration, US government scientists warned even more sea level rise is expected by century's end than previously estimated, due to rapid ice sheet melting at the poles.

Meteorites did not enrich ocean life: study

January 24, 2017

An explosion of ocean life some 471 million years ago was not sparked by a meteorite bombardment of Earth, said a study Tuesday that challenges a leading theory.

Swarm of underwater robots mimics ocean life

January 24, 2017

Underwater robots developed by researchers at Scripps Institution of Oceanography at the University of California San Diego offer scientists an extraordinary new tool to study ocean currents and the tiny creatures they transport. ...

Are we ready for another massive volcanic eruption?

January 24, 2017

An enormous volcanic eruption would not necessarily plunge the world into a new societal crisis, according to a new study of the biggest eruption of the last millennium published in Nature Geoscience.

3 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

FrankHerbertWhines
1 / 5 (5) Feb 28, 2013
try using real science not some enviro rag funded by NERC
VendicarE
5 / 5 (4) Feb 28, 2013
A laughable statement from a whiner who's nation's grain belt is rapidly reverting to desert conditions.

Don't come to me begging for food.
Maggnus
4.3 / 5 (6) Feb 28, 2013
Atta boy FHW, blame the messenger.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.