Climate change poses risk to food supplies

United Nations scientists have found climate change will pose sharp risks to the world’s food supply in coming decades.

As a result it will potentially undermine crop production and drive up prices at a time when the demand for food is expected to soar.

In a departure from an earlier assessment, the scientists concluded that rising temperatures will have some beneficial effects on crops in some places, but that globally they will make it harder for crops to thrive.

The result could perhaps reducing production over all by as much as two per cent each decade for the rest of this century, compared with what it would be without climate change.

At the same time, the scientists say, they are already seeing the harmful effects in some regions.

The warnings come in a leaked draft of a report under development by the UN Intergovernmental Panel on Climate Change (IPCC).

The document is not final and could change before it is released in March.

The report also finds other sweeping impacts from climate change already 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 colonize new areas to escape rising temperatures, and warn that many could become extinct.

The warning on the food supply is the sharpest in tone the panel has 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 most 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 heat waves.

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.

The IPCC is the principal scientific body charged with reviewing and assessing climate science, and then issuing reports about the risks to the world’s governments.

Its main reports come out every five to six years.

On food supply, the new report finds that benefits from global warming may be seen in some areas, like northern lands that are now marginal for food production.

However, it adds that over all, global warming could reduce agricultural production by as much as two 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.

The UN projects the world population will grow to 9.6 billion in 2050, from 7.2 billion today, and at the same time many of those people in developing countries will acquire the money to eat richer diets.

Any shortfall would lead to rising food prices that would hit the world’s poor hardest, as has already occurred from price increases of recent years.

Research has found that climate change, particularly severe heat waves, 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.

The report finds that efforts to adapt to climate change have already begun in many countries.

The document also finds that it is not too late for cuts in emissions to have a strong impact on the future risks of climate change, though the costs would be incurred in the next few decades and the main benefits would probably be seen in the late 21st century and beyond.

The leak of the new draft occurred on a blog hostile to the IPCC and a spokesman for the panel, Jonathan Lynn, did not dispute the authenticity of the document.

“It’s a work in progress,” Mr. Lynn said. “It’s likely to change.”

A third IPCC report, analysing potential ways to limit the rise of greenhouse gases, is due for release in Berlin in April.