Global warming could reshape global agriculture

by Meyer Sosland
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Agriculture, perhaps more than any other industry, is affected by changes in climate. Just how the increased temperatures expected by scientists will change grain production around the world is a question that is beginning to occupy farmers and consumers of grain alike.

"There is an overwhelming consensus that the climate change projections are correct," said Pete Falloon, Climate Impact Specialist with the United Kingdom’s Meteorological Office, at the Home Grown Cereals Authority’s recent Grains Market Outlook Conference. "There’s a more mixed view on whether it is a threat or an opportunity."

One organization that is hoping climate change will present new opportunities is Britain’s National Farmers Union (NFU). "The way the NFU is looking at it is to say that we need to be ready to adapt," Jo Hughes, NFU Climate Change Advisor, told World Grain. "We’re looking at it as more of an opportunity than the doom and gloom you see in the newspaper. You might be able to turn it round to your advantage."

"Obviously we’re expecting it to get warmer," she said. "We’re expecting less rain in the southeast and more in the northwest. It’s the extreme events that people are going to struggle to adapt to."

According to Falloon, temperatures around the world have been rising since the mid-19th century. "The change in temperature that we’ve seen since the Industrial Revolution is very dramatic and is quite unprecedented," he said. Even since the 1960s, there have been much shorter cold spells as well as longer periods of heatwave. There have been many more sunny days and a big reduction in the number of air frost days. For farmers, there has also been a lengthening of the growing season.

"A warming climate means a longer growing season in general," he said. "Higher concentrations of CO(carbon dioxide) mean that plants generally can grow better."

The United Nations Intergovernmental Panel on Climate Change (IPCC) got this year’s Nobel Peace Prize, shared with former United States (U.S.) Vice-President Al Gore, for "their efforts to build up and disseminate knowledge about man-made climate change," The IPCC’s latest working group report on "Impacts, Adaptation and Vulnerability," goes into detail on how agriculture will be affected around the world.

According to the IPCC, a rise in temperature of 1 to 2 degrees C would raise agricultural prices by between 10% and 30%.

"In mid- to high-latitude regions, moderate to medium local increases in temperature (1 degree C to 3 degrees C), across a range of CO concentrations and rainfall changes, can have small beneficial impacts on the main cereal crops," the IPCC said. "Further warming has increasingly negative impacts.

"In low-latitude regions, these simulations indicate that even moderate temperature increases are likely to have negative yield impacts for major cereal crops. For temperature increases more than 3 degrees C, average impacts are stressful to all crops assessed and to all regions."

The IPCC suggests that crop yield is threatened by a local temperature rise of 1 degree C and that it can accommodate no more than plus 3 degrees C before starting to fall. Changes in rainfall and associated changes in precipitation to evaporation ratios as well as COresponses may affect crop yield responses.

African farmers have already developed ways of coping with variations in climate, but it may not be enough to handle what is coming in the future, the IPCC said. "Agricultural production and food security (including access to food) in many African countries and regions are likely to be severely compromised by climate change and climate variability," it said.

"A number of countries in Africa already face semi-arid conditions that make agriculture challenging, and climate change will likely reduce the length of the growing season as well as force large regions of marginal agriculture out of production," it said. "Projected reductions in yield in some countries could be as much as 50% by 2020, and crop net revenues could fall by as much as 90% by 2100, with small-scale farmers being the most affected. This would adversely affect food security in the continent."

In Asia, future climate change is likely to affect agriculture, risk of hunger and water resource scarcity with enhanced climate variability and more rapid melting of glaciers, it said.

"About 2.5% to 10% decrease in crop yield is projected for parts of Asia in the 2020s and a 5% to 30% decrease in the 2050s compared with 1990 levels without CO effects," it said. "Fresh

water availability in Central, South and Southeast Asia, particularly in large river basins such as Changjiang, is likely to decrease due to climate change, along with population growth and rising standard of living that could adversely affect more than 1 billion people in Asia by the 2050s.

"An additional 49 million, 132 million and 266 million people of Asia could be at risk of hunger by 2020, 2050 and 2080, respectively," it said.

According to the IPCC, Australia and New Zealand are already experiencing impacts from recent climate change. "These are now evident in increasing stresses on water supply and agriculture, changed natural ecosystems, reduced seasonal snow cover, and glacier shrinkage," it said.

In New Zealand, the IPCC expected the COresponse to more than compensate for a moderate increase in temperature for crops like wheat.

Australia is likely to see regional variations. "Southwestern Australian regions are likely to have significant yield reductions by 2070," it said. "In contrast, regions in northeastern Australia are likely to have moderate increases in yield." IPCC projects a fall in the median yield.

But there is the potential for Australia to adapt "Adaptation through changing planting dates and varieties is likely to be highly effective," it said.

"Climate change is likely to change land use in southern Australia, with cropping becoming non-viable at the dry margins if rainfall is reduced substantially, even though yield increases from elevated COpartly offset this effect," it said. "In contrast, cropping is likely to expand into the wet margins if rainfall declines. In the north of Australia, climate change and COincreases are likely to enable cropping to persist."

The IPCC also believed that grain quality would be affected. "Firstly, elevated COreduces grain protein levels. Significant increases in nitrogenous fertilizer application or increased use of pasture legume rotations would be needed to maintain protein levels," it said. "Secondly, there is increased risk of development of undesirable heat-shock proteins in wheat grain in both northern and southern cropping zones with temperature increases greater than 4 degrees C."

Climate change is expected to have an effect on many sections of the European economy, according to the IPCC. "Agriculture will have to cope with increasing water demand for irrigation in southern Europe and with additional restrictions due to increases in croprelated nitrate leaching,

"Short-term adaptation of agriculture in southern Europe may include changes in crop species (such as replacing winter with spring wheat), cultivars (higher drought resistance and longer grain filling) or sowing dates," it said. "Introducing new crops and varieties are also an alternative for northern Europe, even if this option may be limited by soil fertility, for example in northern Russia. A feasible long-term adaptation measure is to change the allocation of agricultural land according to its changing suitability under climate change."

The IPCC raised the possibility of large-scale abandonment of cropland in Europe although it did see an opportunity to increase the cultivation of bioenergy crops.

"It is indisputable that the reform of E.U. agricultural policies (such as its stance on GM crops) will be an important vehicle for encouraging European agriculture to adapt to climate change and for reducing the vulnerability of the agricultural sector," it said.

"Generalized reductions in rice yields by the 2020s, as well as increases in soybean yields, are possible when CO effects are considered," the IPCC said. "For other crops (wheat, maize), the projected response to climate change is more erratic, depending on the chosen scenario."

One scenario put forward by the IPCC has the number of additional people at risk of hunger at 5 million, 26 million and 85 million in 2020, 2050 and 2080, respectively. "On the other hand, cattle and dairy productivity is expected to decline in response to increasing temperatures," it said.

According to one assessment, if COeffects are not considered, grain yield reductions could reach up to 30% by 2080. "However, if direct COeffects are considered, yield changes could range between reductions of 30% in Mexico and increases of 5% in Argentina," it said.

The IPCC suggested that research backs the idea that moderate climate change will likely increase yields of North American rain-fed agriculture, but with smaller increases and more spatial variability than in earlier estimates. "Most studies project likely climate-related yield increases of 5% to 20% over the first decades of the century, with the overall positive effects of climate persisting through much or all of the 21st century," it said. "This pattern emerges from recent assessments for corn, rice, sorghum, soybean, wheat, common forages, cotton and some fruits."

"For U.S. soybean yield, adjusting the planting date can reduce the negative effects of late season heat stress and can more than compensate for direct effects of climate change," it said.

"Water access is the major factor limiting agriculture in southeast Arizona, but farmers in the region perceive that technologies and adaptations such as crop insurance have recently decreased vulnerability," it said. "Areas with marginal financial and resource endowments (such as the U.S. northern plains) are especially vulnerable to climate change."

"Unsustainable land-use practices will tend to increase the vulnerability of agriculture in the U.S. Great Plains to climate change." WG

Chris Lyddon is World Grain’s European editor. He may be contacted at: