         
Original article by Alison Colls.
A detailed look at some of the worldwide agricultural impacts of climate change.
Introduction Changes in climate and climate variability have a profound impact on agriculture and food production. Predicted global warming will have both a positive and a negative impact on agriculture. The ability of farmers and rural societies to adapt to these changes is crucial to maintaining adequate global food supply. This article will look at some of the likely impacts of climate change and the mechanisms for adapting to it.
Weeding in Zimbabwe Sections in this article The problem for farmers Some basic impacts to consider The global picture The picture in Europe The scientific response How can farmers adapt? Adapting without making the problem worse Where next? The problem for farmers Farmers are already well used to having to adapt to the vagaries of the climate but if, as scientists are predicting, they have to cope with increasing variability this century their ability to produce food becomes a greater challenge. The Intergovernmental Panel on Climate Change predicts an increase in extreme weather events such as drought, flooding, hail, hurricanes, and tornadoes all of which can wreak havoc on crops. Without reliable regional forecasts of such events, farmers may be making decisions as basic as what to plant, where to plant and when to plant, in the dark. Nor can they make adequate preparations to mitigate these extreme impacts. But climate change need not be all bad news for agriculture. Rising temperatures, for instance, may increase drought damage to crops in some areas; elsewhere they could have the benefit of decreasing frost damage. If agriculturalists come to understand more about how projected climate change could affect growing seasons (the length of time that soil temperature and soil moisture conditions are suitable for crop growth) they may be able to make a better choice about the type and species of crops that can be grown in a given region.
Drought resistance Some basic impacts to consider Soil: climate change is likely to have a variety of impacts on soil quality. In areas where winter rainfall becomes heavier some soils may become more susceptible to erosion. Other changes include the washing away of organic matter and leaching of nutrients and in some areas, particularly those facing an increase in drought conditions, saltier soil. Fertilisation: higher concentrations of carbon dioxide enable plants to use water more efficiently and grow more, the so called "carbon fertilisation effect". Of course this benefits weeds as well as food crops and according to the US Department of Agriculture, the detrimental effects of other fossil fuel emissions (e.g. sulphur dioxide, ozone) will offset some of the benefits of high carbon dioxide concentrations.
Diamonded black moth infestation. Just one of the many pests which may be affected by climate change. Pests: and vector-borne diseases are predicted to spread into areas where they were previously unknown. Livestock: production could be affected by changes in the prevalence and distribution of livestock pests, and changes in grazing and pasture productivity. Livestock are sensitive to stress from warmer, drier conditions, as well as any reduction in the quality and availability of their food and water. Where winters become warmer it may make it easier for range livestock to survive. Sea Level: a rise in sea levels is likely to reduce the amount of land available for agriculture. Rises in sea level threaten ecosystems such as mangrove forests, which are especially diverse. The mangrove forests along the Indus Delta in Pakistan, for example, are the breeding grounds for an estimated 90% of shrimps, Pakistan's main fisheries export. Slight changes in environmental variables, such as temperature, salinity, wind speed and direction, ocean currents, and predators can sharply alter the abundance of fish populations. The global picture The impact of future climate change on food production is variable but overall there is a degree of consensus among scientists that global yields are expected to decrease. Research from the International Institute of Applied Systems Analysis attempts to identify which countries will be hardest hit. In the worst-case scenarios some countries will be even more exposed to food shortages, malnutrition and hunger. In the so-called ‘losers' category it is hardly surprising that developing countries with the fewest resources are less likely to be able to adapt to changing agricultural conditions and food shortages. Furthermore, in 2001 the Intergovernmental Panel on Climate Change stated that the extent to which agricultural systems are affected might depend on the amount of warming that takes place. In the mid latitudes, if global warming is less than a few degrees Celsius, climate change may have a generally positive impact on food production. If warming is greater than a few degrees, the effects will be predominantly negative. The Panel's report goes on to say that in tropical regions and especially in Africa, change is expected to be negative, even at the lower end of the predicted warming.
Africa is already heavily dependent on foreign food imports and its rural populations are the most vulnerable and least able to adapt. The picture in Europe
Maize field in France In Europe, agricultural systems are very advanced and are expected to be able to adapt to climate change. There is, for instance, potential for north and eastward expansion of crops such as maize and sunflowers, which are vulnerable to adverse weather conditions, particularly low soil temperatures. In the UK the growth of maize is currently close to its environmental limits, but higher temperatures will make it easier to grow in this part of the world. Meanwhile, increasing temperatures may have a detrimental effect on other crops such as potatoes, which are sensitive to hot, dry summers. A significant and increasing proportion of the UK's root and vegetable harvest is produced using irrigation, partly in response to supermarket demand for a consistent high quality product, but also in response to the more frequent occurrence of dry growing seasons in recent years. The scientific response In response to the challenges posed by climate change, scientists are trying harder to monitor and predict crop/agricultural responses. Researchers use controlled-conditions experiments and crop simulation models to predict future food production taking different climate scenarios into account. The reliability and precision of crop simulations is limited by the lack of detail available from the global climate models, which are currently not able to project local-scale changes in climate that are of interest to agriculture. Furthermore, crop model simulations, designed to assess the risks of agricultural production from climate change, do not incorporate variables such as the possibility of extreme events, diseases and pests. However, the ability to predict seasonal droughts and rainfalls is increasing. Such forecasts are operational in Africa, where a forecast with a lead-time of several months can help mitigate the impacts of a drought. How can farmers adapt? Land use and management have been shown to have a greater impact on soil conditions than the effects of climate change, so adaptation has the potential to significantly mitigate these impacts. The IPCC Impacts and Adaptation Report, 2001 lists the following as some of the actions farmers can take:
Adapting without making the problem worse
Herding cattle in East Africa While agriculture has to adapt to climate change, it has to do so in a way that does not exacerbate the problem. Agricultural activities currently contribute significant amounts of greenhouse gases to the atmosphere: carbon dioxide, via deforestation and burning; methane, via livestock and rice production; and nitrous oxide via use of fertilisers and pesticides. In 2001, The Intergovernmental Panel on Climate Change estimated greenhouse gas emissions from agricultural sources to account for some 25% of today's anthropogenic greenhouse gas emissions. These emissions are only likely to increase in the future, given the necessity to expand food production in order to provide for the world's growing population. The challenge is to continue improving yields while at the same time adapting to climate change and reducing, or at least, stabilising greenhouse gas emissions. Where next? On ClimateX.org A series of articles by Mahendra Shah from the International Institute for Applied Systems Analysis focuses on current research into food production and climate change. Read ‘Food in a Climate of Disparity' for some highlights, with kind permission of the author. For further publications by Mashendra, see the International Institute for Applied Systems Analysis. External links Food and Agriculture Organisation (FAO) Information Sheet 4: Indicators of climate change in the UK Palukitof, J. 2000 Intergovernmental Panel on Climate Change website to download publications used as source material for this article. Author, Alison Colls, also drew on information from publications which you might want to track down in your nearest library: Gregory, P. J. and Ingram, J. S. I. 2000 Agriculture, Ecosystems and Environment 82, 3-14 Karim, Hussain and Ahmed (1996) Assessing Impacts of Climate Variations on Foodgrain Production in Bangladesh. In Erda L et al. (eds) Climate Change Variability and Adaptation in Asia and the Pacific. Dordrecht, The Netherlands: Kluwer Academic Publishers. Article by
Alison Colls
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