Global warming – impact of climate change on global agriculture
(Last in a Series)
Our efforts to mitigate the effects of climate change, urgent as they are, will have little effect over the next 50 years. Changes during this period have already been set in motion by past greenhouse gas emissions.
Limiting greenhouse gas emissions will only affect climate change in the long-term (beyond 50 years). So we must learn to adapt to the changes in climate that will occur over the next 50 years.
In the previous article we listed several estimated changes we may expect to see in the Midwest and possible impacts on Midwest agriculture. In this article we will examine the rest of the world. We will identify expected changes in major agricultural regions around the world.
Suitability for rainfed agriculture
It takes large amounts of water to produce grain. But suitable soil and terrain also are necessary for successful agricultural production. Let’s take a look at regions of the world that have a “high suitability for rainfed agriculture”. This suitability factor depends on the amount of precipitation, the availability of soils suitable for agriculture, and terrain that allows for agricultural production.
An index of the suitability for rainfed agriculture is shown on the world map in Figure 1. The circled areas show a high suitability index.
From this we can see the regions of the world that are highly suitable for rainfed agriculture. They include the U.S. Midwest and Great Plains, Europe and European Russia, India, Southeast Asia, southern and eastern Brazil including the Pampas of Argentina, sub-saharan Africa, and the rim of Australia. These are the traditional agricultural producing regions of the world that have allowed human population to flourish and grow.
The population density of various parts of the world is shown in Figure 2. In many instances, areas suitable for rainfed agriculture match the areas of high population density. This includes Europe, Eastern U.S., India, China, and Southeast Asia. Other regions, such as southern Mexico, the Middle East, parts of China, and regions bordering the Nile River, have high populations but low suitability for rainfed agriculture and therefore must rely on either irrigation or food imports. Changes in the suitability index for rainfed agriculture due to climate change can affect the ability of large areas of the world to feed themselves.
Projected precipitation changes
The latest International Panel on Climate Change (IPCC) report outlines potential changes in rainfall patterns over the 21st century. Although this represents the best available science, there still are uncertainties about the projections. However, considerable research currently is focused on this issue. So, more reliable estimates will be forthcoming.
By looking at the projected changes in precipitation due to climate change over the next hundred years (Figure 3), we see there will be winners and losers. The dark shaded areas show increased changes (either increase or decrease) in precipitation.
Since soils and terrain will not change, changes in the suitability index for rainfed agriculture depend on changes in rainfall during the growing season. The suitability index will increase in some areas and decrease in others. A decrease in precipitation will usually result in a decline in the suitability index. However, an increase in precipitation may or may not improve the suitability index. If the precipitation increase leads to more flooding or water-logging of soils, the suitability index will decline. Also, changes in precipitation will increase a region’s suitability index only if it has suitable soils and terrain.
To help us focus on the areas with suitable soils and terrain, we have pointed out these areas in Figures 3 and 4. Areas with increased rainfall are marked with a square around them. Areas with decreased rainfall are circled.
The IPCC has not evaluated how the suitability index will change due to climate change rainfall projections. Discussions are underway to launch such an effort. However, we can at least make a simplistic estimate of the future of global agricultural production based on projected changes in precipitation.
Of the seven major regions with a high or moderate suitability index (Figure 1), we can see that:
1) The central U.S. will likely experience a modest decrease, particularly in the Great Plains,
2) Mexico and Central America will likely experience a significant decrease. This decline in precipitation is a feature of all global climate models. Because of the magnitude of this impact on our neighbors to the south, our U.S. national policy makers should monitor climate change over this region through the coming years.
3) Brazil, Uruguay, and Argentina might see an increase in rainfall that likely will be beneficial,
4) Southern and eastern Europe likely will see a substantial decrease,
5) Central Africa likely will see an increase and southern Africa a decrease,
6) India probably will experience an increase.
7) China and East Asia will probably experience an increase. However, the likelihood of extreme increases in precipitation in these areas may be detrimental to agricultural production.
8) Australia is projected to see an increase in the east and a decrease in the west. Regions with a long history of cereal production, such as Australia, are already facing new challenges (Reuters, 2008). Six continuous years of drought have reduced Australia’s rice crop by 98 percent and has shut down processing plants (Bradsher, 2008).
Climate change also will lead to an increase in temperature that will affect agricultural production. However, it is difficult to evaluate whether temperature increases due to climate change will allow new regions such as northern Russia and Canada to expand production.
Adapt by using irrigation
Can we adapt to reduced rainfall by irrigating? Although irrigation can provide a short-term solution (a few decades), it does not provide a permanent or sustainable solution. A colleague made the observation that, of all former civilizations that depended on irrigated agriculture for their food supply, none have survived. In the modern world we see numerous regions with widespread irrigation facing challenges relating to water supply (e.g., aquifer depletion, competing uses for reservoir water) or salinization of land under long-term irrigation.
A recent example is Saudi Arabia (Elhadj, 2008), which, having an annual rainfall of only 3-4 inches, discovered in the early 1980s what was thought to be substantial groundwater reserves. By 1992 they were irrigating about 2.5 million acres and producing 4.1 million tons of wheat. But by 2000, the average cost of raising wheat in Saudi Arabia rose to $500 per ton - four times what it cost to buy it on the world market. On January 8, 2008, the Saudi government abandoned its food independence strategy and decided instead to import the country’s entire wheat needs by 2016.
So, in the long-term, we will depend on rainfed agriculture. This means we must adapt our agricultural systems to the changes that a changing climate has in store for us.
We emphasize that, although the research summarized by the latest IPCC report represents the best available science, there are still uncertainties in the projections summarized here. However, climate change will have a significant impact on world agriculture regardless of the specific implications for various growing regions.
Because of the global nature of agricultural markets, agricultural trade patterns may shift. U.S. producers must address both the impact of climate change on their own operations and respond to market signals created by the impact of climate change on agricultural production around the world.
These projected changes in rainfall patterns and the resulting changes in the suitability index for rainfed agriculture provide us with a tool for anticipating the impact of climate change on various agricultural regions of the world. By focusing our attention on the regions of the world where climate change will negatively affect agricultural production, we can develop strategies for adapting to these changes that will help reduce the negative impact on food production in the coming decades.
These strategies must focus on agricultural research and development, including investment in new technologies that can reduce the impact of climate change. Although countries must make these investments individually, a need will arise for a worldwide collaboration to address these issues on a global basis.
Bradsher, K. 2008. As Australia dries, a global shortage of rice. Published April 17, 2008. Accessed September 4, 2008: http://www.nytimes.com/2008/04/17/business/worldbusiness/17iht-17warm.12077306.html.
Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Accessed September 4, 2008: http://www.ipcc.ch/ipccreports/ar4-wg1.htm
Climate Change 2007 - Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Accessed September 4, 2008: http://www.ipcc.ch/ipccreports/ar4-wg2.htm
Elhadj, E. 2008. Saudi Arabia’s Agricultural Project: From Dust to Dust. Accessed September 4, 2008: http://www.meriajournal.com/en/asp/journal/2008/june/elhadj/index.asp.
Fischer, G., M. Shah, M. van Velthuizen, and F. O. Nachtergaele. 2001. Global Agro-ecological Assessment for Agriculture in the 21st Century. International Institute for Applied Systems Analysis, Laxenburg, Austria.
Perry, M. 2008. Winners and losers in Australian climate change. Reuters.com. Accessed September 4, 2008: http://www.reuters.com/article/latestCrisis/idUSSYD156225.