<P> Evan Fraser, a geographer at the University of Guelph in Ontario, Canada, explores the ways in which climate change may affect future famines . To do this, he draws on a range of historic cases where relatively small environmental problems triggered famines as a way of creating theoretical links between climate and famine in the future . Drawing on situations as diverse as the Great Irish Potato Famine, a series of weather induced famines in Asia during the late 19th century, and famines in Ethiopia during the 1980s, he concludes there are three "lines of defense" that protect a community's food security from environmental change . The first line of defense is the agro-ecosystem on which food is produced: diverse ecosystems with well managed soils high in organic matter tend to be more resilient . The second line of defense is the wealth and skills of individual households: If those households affected by bad weather such as drought have savings or skills they may be able to do all right despite the bad weather . The final line of defense is created by the formal institutions present in a society . Governments, churches, or NGOs must be willing and able to mount effective relief efforts . Pulling this together, Evan Fraser argues that if an ecosystem is resilient enough, it may be able to withstand weather - related shocks . But if these shocks overwhelm the ecosystem's line of defense, it is necessary for the household to adapt using its skills and savings . If a problem is too big for the family or household, then people must rely on the third line of defense, which is whether or not the formal institutions present in a society are able to provide help . Evan Fraser concludes that in almost every situation where an environmental problem triggered a famine you see a failure in each of these three lines of defense . Hence, understanding how climate change may cause famines in the future requires combining both an assessment of local socio - economic and environmental factors along with climate models that predict where bad weather may occur in the future </P> <P> Definitions of famines are based on three different categories--these include food supply - based, food consumption - based and mortality - based definitions . Some definitions of famines are: </P> <Ul> <Li> Blix--Widespread food shortage leading to significant rise in regional death rates . </Li> <Li> Brown and Eckholm--Sudden, sharp reduction in food supply resulting in widespread hunger . </Li> <Li> Scrimshaw--Sudden collapse in level of food consumption of large numbers of people . </Li> <Li> Ravallion--Unusually high mortality with unusually severe threat to food intake of some segments of a population . </Li> <Li> Cuny--A set of conditions that occurs when large numbers of people in a region cannot obtain sufficient food, resulting in widespread, acute malnutrition . </Li> </Ul> <Li> Blix--Widespread food shortage leading to significant rise in regional death rates . </Li>

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