Global warming a risk to food supply, says draft United Nations report
Climate change will pose sharp risks to the world's food supply in coming decades, potentially undermining crop production and driving up prices at a time when demand for food is expected to soar, scientists have found.
In a departure from an earlier assessment, the scientists concluded that rising temperatures would have some beneficial effect on crops in some places, but that globally, they would make it harder for crops to thrive.
And, the scientists said, they were already seeing the harmful effects in some regions.
The warnings come in a leaked draft of a report under development by a UN panel, the Intergovernmental Panel on Climate Change. The document is not final and could change before it is released in March.
The report also finds other sweeping impacts from climate change occurring across the planet, and warns that these are likely to intensify as human emissions of greenhouse gases continue to rise. The scientists describe a natural world in turmoil as plants and animals attempt to migrate to escape rising temperatures, and warn that many could become extinct.
The warning on the food supply is the sharpest in tone that the panel has ever issued. Its previous report, in 2007, was more hopeful. While it did warn of risks and potential losses in output, particularly in the tropics, that report found that gains in production at higher latitudes would likely offset the losses and ensure an adequate global supply.
The new tone reflects a large body of research in recent years that has shown how sensitive crops appear to be to heatwaves. The recent work also challenges previous assumptions about how much food production could increase in coming decades because of higher carbon dioxide levels in the atmosphere. The gas, though it is the main reason for global warming, also acts as a kind of fertiliser for plants.
On the food supply, the report finds that benefits from global warming may be seen in some areas, like northern lands that are now marginal for food production. But it adds that overall, global warming could reduce agricultural production by as much as 2 per cent each decade for the rest of this century.
During that period, demand is expected to rise as much as 14 per cent each decade, the report found, as the world population is projected to grow to 9.6 billion in 2050 from 7.2 billion today, and many of those people in developing countries acquire the money to eat richer diets.
Any shortfall would lead to rising food prices that would hit the world's poor hardest. Research has found that climate change, particularly severe heatwaves, was a factor in those price spikes.
The agricultural risks "are greatest for tropical countries, given projected impacts that exceed adaptive capacity and higher poverty rates compared with temperate regions," the draft report finds.
If the report proves to be correct about the effect on crops from climate change, global food demand might have to be met - if it can be met - by putting new land into production. That could entail chopping down large areas of forest, an action that would only accelerate climate change by sending substantial amounts of carbon dioxide into the air.