Half of the world's population could face severe food shortages by the end of the century as rising temperatures take their toll on farmers' crops, scientists have warned.
of staple food crops such as rice and maize could fall by between 20%
and 40% as a result of higher temperatures during the growing season in
the tropics and subtropics. Warmer temperatures in the region are also
expected to increase the risk of drought, cutting crop losses further,
according to a new study.
The worst of the food shortages are
expected to hit the poor, densely inhabited regions of the equatorial
belt, where demand for food is already soaring because of a rapid
growth in population.
A study in the US journal Science found
there was a 90% chance that by the end of the century, the coolest
temperatures in the tropics during the crop growing season would exceed
the hottest temperatures recorded between 1900 and 2006.
More temperate regions such as Europe could expect to see previous record temperatures become the norm by 2100.
stress on global food production from temperatures alone is going to be
huge, and that doesn't take into account water supplies stressed by the
higher temperatures," said David Battisti, at the University of
Washington, who led the study.
Battisti and Rosamond Naylor, at Stanford University in California, combined climate models from the Intergovernmental Panel on Climate Change
(IPCC) and historical examples of the impact of heatwaves on
agriculture, and found severe food shortages were likely to become more
Among the periods they examined was the record heatwave
across western Europe in 2003, which killed an estimated 52,000 people
and also cut yields of wheat and fodder by a third. In 1972, a
prolonged hot summer in south-east Ukraine and south-west Russia saw
temperatures rise by between 2C and 4C above the norm, driving down
wheat and coarse grain yields for the whole of the USSR by 13%. The
disruption affected the global cereal market for two years.
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who is director of food security and the environment at Stanford, said
the study emphasised the need for countries to invest in adapting to a
changing climate. To develop new crops to withstand higher temperatures
could take decades, she added.
"When we looked at our
historical examples there were ways to address the problem within a
given year," Naylor said. "People could always turn somewhere else to
find food. But in the future there's not going to be any place to turn
unless we rethink our food supplies."
The tropics and
subtropics, which stretch from the southern US to northern Argentina
and southern Brazil, from northern India and southern China to southern
Australia, and cover all of Africa, are currently home to 3 billion
people. Future temperature rises are expected to have a greater impact
in the tropics because the crops grown there are less resilient to
changes in climate.
According to the study, many local
populations now live on less than £1.30 a day and depend on
agriculture. The need for food is due to become more urgent as
populations are expected to nearly double by the end of the century.
all the signs point in the same direction, and in this case it's a bad
direction, you pretty much know what's going to happen," Battisti said.
"You're talking about hundreds of millions of additional people looking
for food because they won't be able to find it where they find it now.
can let it happen and painfully adapt, or you can plan for it. You
could also mitigate [climate change] and not let it happen in the first
place, but we're not doing a very good job of that."
added: "We have to be rethinking agriculture systems as a whole, not
only thinking about new varieties [of crops], but also recognising that
many people will just move out of agriculture, and even move from the
lands where they live now."
In many countries, a combination of
poor farming practices and deforestation, exacerbated by climate
change, may steadily degrade soil fertility, leaving vast areas
unsuitable for crops or grazing. In 2007, scientists warned that poor
soil fertility meant a global food crisis was likely in the next