Droughts and heatwaves have reduced cereal harvests by an average of about 10 per cent globally over the past half century, and their impact has become stronger in recent decades especially in developed countries, a study has found.
Climate change is expected to increase the risk of severe drought and extreme heat and now the first detailed analysis of global cereal production has shown that harvests of wheat, maize and rice have suffered greater losses since the 1980s from drought and heat compared to previous decades.
The findings question whether increased levels of carbon dioxide in the atmosphere are having a discernible “fertilising effect” on crop production that could outweigh the damaging effect on harvests caused by extreme weather events such as droughts and heatwaves exacerbated by global warming.
An analysis of national production of 16 different cereal crops in 177 countries, and a comparison with the effects of about 2,800 weather disasters between 1964 and 2007, has for the first time provided a detailed snapshot of how extreme weather has affected overall cereal production globally, scientists said.
The study found that drought and heatwaves reduced cereal harvests by between 9 per cent and 10 per cent on average in the affected countries. However, the technically advanced arable farms of North America, Europe and Australia were even more strongly affected than the developing world, with average production cuts of about 20 per cent.
“We found that extreme weather disasters such as droughts and heatwaves substantially reduce crop production, and the impacts are worse in richer countries,” said Pedram Rowhani of Sussex University and a co-author of the study.
“The frequency and severity of these extreme weather events is expected to increase in the future. If we do not adapt our agricultural systems to become more resilient to these shocks we can anticipate even larger losses in the future,” Dr Rowhani said.
The analysis, published in the journal Nature, found that losses in average cereal producton caused by more recent droughts had increased in more recent years, with average reductions of about 13.7 per cent compared to losses of about 6.7 per cent prior to the mid-1980s. However, the analysis also showed that cereal production soon bounced back after a drought year.
Climate change around the world - in pictures
Climate change around the world - in pictures
Calved icebergs from the nearby Twin Glaciers are seen floating on the water in Qaqortoq, Greenland
2/17 Coastal systems and low-lying areas
Flood damaged streets in Queens, New York where the historic boardwalk was washed away due to Hurricane Sandy in 2012. The report predicts that by the end of the century “hundreds of millions of people will be affected by coastal flooding and displaced due to land loss”
3/17 Food security
Widespread drought devastated a corn crop on a farm near Bruceville, Indiana in 2012. The report forecasts that climate change will reduce median yields by up to 2 per cent per decade for the rest of the century
4/17 The global economy
The Evening Standard headline board showing the words 'Black Friday Shares Crash' in London in October 2008 in London. The report warns a global mean temperature increase of 2.5C above pre-industrial levels may lead to global aggregate economic losses of between 0.2 and 2.0 per cent
5/17 Human health
A child suffering from malnutrition and diarrhoea is seen at the Banadir hospital in the Somalian capital of Mogadishu in 2009. Climate change will lead to increases in ill-health in many regions, with examples including an increased likelihood of under-nutrition.
6/17 Human security
A Muslim migrant holds his son as they are detained at the Immigration Police Office on the Thai-Malaysian border in March 2014. The report states that climate change over the 21st century will have a significant impact on forms of migration that compromise human security
7/17 Freshwater resources
A villager walks through a parched paddy in Tianlin county, China in 2012. The report finds that climate change will “reduce renewable surface water and groundwater resources significantly in most dry subtropical regions"
8/17 Unique landscapes
Machair, a grassy coastal habitat found only in north-west Scotland and the west coast of Ireland, is one of the several elements of the UK’s “cultural heritage” that is at risk from climate change
A boat navigates among calved icebergs from the nearby Twin Glaciers in Qaqortoq, Greenland. Boats are a crucial mode of transportation in the country that has few roads. As cities like Miami, New York and other vulnerable spots around the world strategize about how to respond to climate change, many Greenlanders simply do what theyve always done: adapt. 'Were used to change, said Greenlander Pilu Neilsen. 'We learn to adapt to whatever comes. If all the glaciers melt, well just get more land
The Svalbard Global Seed Vault is seen after being inaugurated in Longyearbyen, Norway. The 'doomsday' seed vault built to protect millions of food crops from climate change, wars and natural disasters opened deep within an Arctic mountain in the remote Norwegian archipelago of Svalbard
A technician preparing to drain a vast underground lake at the Tete Rousse glacier on the Mont Blanc Alpine mountain, to avert a potentially disatrous flood. Some 65,000 cubic metres (2.3 million cubic feet) of water have gathered in a cavity, dangerously raising the pressure beneath the mountain, a favourite spot for holiday makers in Saint-Gervais-les-Bains
Oroumieh, one of the biggest saltwater lakes on Earth, has shrunk more than 80 percent to 1,000 square kilometers in the past decade. It shrinks mainly because of climate change, expanded irrigation for surrounding farms and the damming of rivers that feed the body of water
Cracked mud is picture at sunrise in the dried shores of Lake Gruyere affected by continous drought near the western Switzerland village of Avry-devant-Pont. A leading climate scientist warned that Europe should take action over increasing drought and floods, stressing that some climate change trends were clear despite variations in predictions
Cattle graze on grassland that remains dry and brown at the height of the rainy season in south of Bakersfield, California. Its third straight year of unprecedented drought, California is experiencing its driest year on record, dating back 119 years, and dating back as far as 500 years, according to some scientists who study tree rings
An aerial view shows tents of flood-displaced people surrounded by water in southern Sehwan town. United Nations Framework Convention on Climate Change (UNFCCC) executive secretary Christiana Figueres met with people displaced by last year's devastating floods. Catastrophic monsoon rains that swept through the country in 2010 and affected some 20 million people, destroyed 1.7 million homes and damaged 5.4 million acres of arable land
An aerial view of flooding in North Wagga Wagga. Climate change is amplifying risks from drought, floods, storm and rising seas, threatening all countries but small island states, poor nations and arid regions in particular, UN experts warned
Damages caused by a landslide on the Pan-American highway near La Moramulca, 55 Km south of Tegucigalpa. International highways have been washed out, villages isolated and thousands of families have lost homes and crops in a region that the United Nations has classified as one of the most affected by climate change
“We have always known that extreme weather causes crop production losses. But until now we did not know exactly how much global production was lost to such extreme weather events, and how they varied by different regions of the world,” said Navin Ramankutty, professor of global food security and sustainability at the University of British Columbia in Canada, and senior author.
One of the most suprising findings was that advanced countries were apparently more susceptible to crop losses due to droughts and heatwaves compared to less advanced nations. This may reflect differences in scale and the farming methods employed in growing and harvesting cereals, the scientists said.
“Across the breadbaskets of North America, for example, the crops and methods of farming are very uniform across huge areas, so if a drought hits in a way that is damaging to those crops, they will all suffer,” said Corey Lesk of McGill University in Montreal, the study’s first author.
“By contrast, in much of the developing world, the cropping systems are a patchwork of small fields with diverse crops. If a drought hits, some of those crops may be damaged, but others may survive,” Mr Lesk said.
Farmers in wealthier countries rarely depend on harvests directly for food, and typically have dependable access to crop insurance in the event of bad weather, he said.
“So the optimal strategy for them may be to maximize yields rather than minimize the risk of weather-related crop damage.”