Global warming will hit developing country agriculture

Posted: 8 October 2007

Author: John Rowley

Global warming will cause great damage to agriculture in the developing world, with falls in productivity between 9 and 21 per cent by 2080, says a detailed new study. The impact will be less in developed countries, but the planet's total agricultural productivity will still decline by between 3 and 16 per cent, as a result of climate change, the research shows.

India is specially at risk, facing losses of 30 per cent by 2080, even under the most optimistic forecast. Other vulnerable regions include Pakistan which faces a loss in agricultural potential of 20 per cent, Latin America (13 per cent), and Africa (17 per cent).

In China the south-central region could face losses of as much as 15 per cent, though taken nationally the effects could range from plus 7 to minus 7 per cent.

These findings are the result of a detailed analysis by William R. Cline, a senior fellow at the Washington-based Center for Global Development and Peterson Institute for International Economics.

Cline says developing countries face much greater falls in productivity because they tend to be located closer to the equator where temperatures are alreasy close to or beyond the thresholds at which further warming will reduce yields, rather than increase them.

Fertilising effect

In developed countries, he says, the change in productivity as a result of unabated global warming will range between a fall 6 per cent to an actual increase in yields of 8 per cent.

The range of forecasts in both developed and developing countries is due to uncertainty over the fertilising effect of increased carbon dioxide in the atmosphere. But, says Cline, field trials show that this effect is considerably less than has previously been supposed. In one recent study, on wheat, field trials showed increases of only 13 per cent compared to lab results of 31 per cent.

Cline says his forecasts are on "the optimistic side" and do not take into account the effects of increased losses from insect pests, more frequent droughts and floods, and the increased scarcity of water for irrigation.

He believes that technological advances will lead to higher yields later in this century even in the face of global warming but points out that demand for agricultural products will be much higher than today. So there is every reason to be worried about the adverse effects of global warming. He singles out four factors which will put pressure on agrcultural output and future food supplies:

Growing population

  • Population growth will continue to rise, so that agricultual production must almost double to keep up.

  • The per capita demand for food woill go up as incomes rise and people want to eat more meat.

  • Increases in yields have slowed in the past 20 years and may slow still further.

  • As much as a third of agricultural land may be converted from food production to energy crops to make ethanol.

    He says the study should inject a new sense of urgency into efforts to reduce carbon emissions. He also believes it has important implications for some countries in particular. Australia, which has been among those resisting the Kyoto Protocol faces losses of 16 per cent, even allowing for the effects of carbon fertilisation. The south-east and south-west plains of the United States also faces "wrenching changes".

    Moreover, he adds, the projections only go to 2080 while the effects of global warming will grow over the rest of the century and beyond, as long as a business-as-usual attitude persists.

    This study is based on William Cline's new book,Global Warming and Agricultural Estimates by Country (Center for Global Development and Peterson Institute for International Economics, Washington DC, 2007)