There is a 90% chance that 3 billion people will have to choose between going hungry and moving their families to milder climes because of climate change within 100 years, says new research.
The study forecasts that temperatures at the close of this century are likely to be above those that crippled food supplies on at least three occasions since 1900.
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, a climatologist at the University of Washington, used 23 models vetted by the to calculate how temperatures will vary with climate change.
Unlike previous studies, his team focused on temperatures during growing seasons around the world. This allowed them to determine the effect on food supplies.
Their results show there is a 90% chance that average temperatures in the tropics and subtropics will be higher than the hottest heat waves of the past century. With more than 3 billion people living in those areas, most of whom rely heavily on locally produced crops for both food and income, the effects could be catastrophic (see maps).
Expanding desert
In the Sahel, the belt of semi-arid land that lies just south of the Sahara, average temperatures between 2080 and 2100 are predicted to be a couple of degrees higher than the hottest temperatures experienced in that region between 1900 and 2006.
This is a region that resembles a desert during the dry season, and where crops can only grow if monsoon rains are sufficient. From the late 1960s to the early 1990s, the Sahel suffered one of the worst droughts in living memory. Although the seasonal monsoon rains have since returned to some parts, temperatures can still be so high that rainwater evaporates before it hits the ground.
鈥淭he Sahel might not be a region that can support agriculture in future,鈥� says Battisti鈥檚 colleague Rosamund Naylor, of Stanford University鈥檚 programme on food security and the environment. Farming currently employs 60% of the population and supplies 40% of the GDP. 鈥淚t is likely that there will be migration out of agricultural areas into rural areas or other countries,鈥� says Naylor. 鈥淲e need to prepare for this.鈥�
Crops hit hard
Poor countries will not be the only ones to suffer. The models suggest that the heat wave which struck Europe in 2003, killing 52,000 people, will become the norm by 2080.
Not only did the 2003 heatwave take lives, it also had long-lasting effects on European food supplies. The highest temperatures hit at the height of the summer growing season. It Italy, maize yields dropped by 36% in one year; in France, fruit harvests were cut by one quarter.
In the summer of 1972, temperatures in southeast Ukraine and southwest Russia were between 2 and 4 掳C higher than the long-term average at the time.
The region represented the former-USSR鈥檚 main breadbasket. The heatwave caused grain production across the USSR to drop by 13%. Instead of dealing with the losses domestically, as it had done previously, the government unexpectedly decided to enter the global market. As a result, global grain prices were affected.
Scientific solution?
鈥淲hat our study shows is that temperatures over land for seasons where the main crops are grown will be way out of norm,鈥� says Naylor. 鈥淭hat is what we have to prepare for.鈥� She adds that if shortages happen at the same time around the world, global food markets will not be able to come to the rescue.
For many agricultural scientists, the solution lies in crops that are either genetically modified or bred to be more heat-resistant.
鈥淔or new varieties to be developed, tested, [and] released, and for seed to become available to farms in significant quantities, it takes more than a decade, in spite of modern tools,鈥� says Marianne Banziger, director of the Global Maize Program at the agricultural research institute .
鈥淲e need to change our investment strategy now, or we are headed towards major food insecurities,鈥� she says.
Journal reference: (DOI: 10.1126/science.1164363)
