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While some of the broad scale features of climate change are well understood, exactly what will happen at local level is more difficult to determine. But when it comes to keeping people fed and healthy, climate scientists and food security analysts agree that some regions could benefit from climate change, while in others it may offset gains in food security from economic and social development.

Climate scientists are confident that the climate is changing and agree on some of the ways it is changing, such as the increasing global average temperature. But the details of what this means on a local scale and the impacts of those changes on other systems, such as agriculture or markets, are more complex. Some projections suggest that 100-200 million additional people could be at risk of hunger due to climate change by 2050. So despite uncertainties in the climate science, it's vital that food security planning decisions are based on the available evidence.

Defining food security

The overall availability of food is affected by changes in agricultural yields as well as by changes in arable land. Changes in food production, together with other factors, are likely to impact food prices and will affect the ability of poor households to access food. Decreased water availability and quality in some areas are likely to result in increased health and sanitation problems, such as diarrhoeal disease. This, together with changes in the patterns of vector-borne disease, has the potential to increase malnutrition by negatively affecting food utilisation.

Analysing food security is based on four aspects:

• Food availability - the physical presence of food through domestic production, commercial imports or food aid. Indicators of changes in food availability might include crop and livestock production trends.
• Food access - a household's ability to acquire adequate amounts of food, through a combination of home production and stocks, purchases, gifts, borrowing and aid. Indicators of food access might include food price trends and market flows.
• Food utilisation - a household's consumption of the food it has access to and the individuals' ability to absorb and metabolise the nutrients. Indicators could include physiological development.
• Food stability - the condition where food is regularly and periodically available and affordable so that it contributes to nutritional security. Indicators of stability include the impact of shocks such as floods and droughts on crop production.

Changes in climate and increases in some extreme weather events, such as floods and droughts, could disrupt stability in the supply of food and people's livelihoods making it more difficult for them to earn a stable income to purchase food.

Hunger and Climate

Vulnerability Index

Experts from the World Food Programme have worked closely with climate scientists from the Met Office Hadley Centre to devise a Hunger and Climate Vulnerability Index.

Using the same definition as the Intergovernmental Panel on Climate Change, 'vulnerability' is defined as: the relationship between the degree of climate stress on populations (exposure); the degree of responsiveness to stress (sensitivity); and the ability of populations to adjust to climatic changes (adaptive capacity).

A map showing the scale of undernourishment across the world and defining hunger and climate vulnerability as 'very low', 'low', 'medium', 'high' and 'very high' illustrates the complex interactions between food security and climate change (see below). The map shows present day levels of food security and vulnerability to weather and climate, alongside rates of undernourishment. Although it is still work in progress, the Hunger and Climate Vulnerability Index could be extended and developed to project how this vulnerability may change in the future, making it a valuable tool to help policy- and decision-makers build resilience and reduce the risk of hunger in future.

Food security poster (PDF, 1 MB)

Information about the sources used to compile the poster (PDF, 195 kB)

Some of the many ways that climate change could affect food security include:

Mean temperature

Average temperatures are expected to increase across the globe in the coming decades. In mid to high latitudes increasing average temperatures can have a positive impact on crop production, but in seasonally arid and tropical regions the impact is likely to be detrimental.

Mean precipitation

On average an increase in global precipitation is expected, but the regional patterns of rainfall will vary: some areas will have more rainfall, while others have less. There are high levels of uncertainty about how the pattern of precipitation will change, with little confidence in model projections on a regional scale. Areas that are highly dependant on seasonal rainfall, and those that are highly dependant on rain-fed agriculture for food security, are particularly vulnerable.

Extreme events

Recurrent extreme weather events such as droughts, floods and tropical cyclones worsen livelihoods and undermine the capacity of communities to adapt to even moderate shock. This results in a vicious circle that leads to greater poverty and hunger. The impacts on food production of extreme events, such as drought, may cancel out the benefits of the increased temperature and growing season observed in mid to high latitudes.

Carbon dioxide fertilisation

Carbon dioxide (CO2) concentrations are known to be increasing. However, the effect of CO2 fertilisation on crop growth is highly uncertain. In particular, there is
a severe lack of experimental work in the Tropics exploring this issue. There is some evidence that although CO2 fertilisation has a positive effect on the yield of certain crops, there may also be a detrimental impact on yield quality.

Drought

Meteorological drought (the result of a period of low rainfall) is projected to increase in intensity, frequency and duration. Drought results in agricultural losses, reductions in water quality and availability, and is a major driver of global food insecurity. Droughts are especially devastating in arid and semi-arid areas, reducing the quality and productivity of crop yields and livestock. Seven hundred million people suffering from hunger already live in semi-arid and arid zones.

Heatwaves

In all regions, one in 20-year extreme temperature events are projected to be hotter. Events that are considered extreme today will be more common in the future. Changes in temperature extremes even for short periods can be critical, especially if they coincide with key stages of crop development.

Heavy rainfall and flooding

While uncertain, it appears that there will be more heavy rainfall events as the climate warms. Heavy rainfall leading to flooding can destroy entire crops over wide areas and devastate food stores, assets (such as farming equipment) and agricultural land (due to sedimentation).

Melting glaciers

Melting glaciers initially increase the amount of water flowing in river systems and enhance the seasonal pattern of flow. Ultimately, however, the loss of glaciers would cause water availability to become more variable year on year as it will depend on seasonal snow and rainfall, instead of the steady release of stored water from the glacier irrespective of that year's precipitation.

Tropical storms

For many regions in the Tropics, a large portion of the annual rain comes from tropical cyclones. However, tropical cyclones also have the potential to devastate a region, causing loss of life and widespread destruction to agricultural crops and lands, infrastructure and livelihoods. Some studies suggest tropical cyclones may become more intense in the future with stronger winds and heavier precipitation. But there is limited consensus among climate models on the regional variation in tropical cyclone frequency.

Sea-level rise

Increases in mean sea-level threaten to inundate agricultural lands and salinise groundwater in the coming decades and centuries. Sea-level rise will also increase the impact of storm surges which can cause great devastation.

Changes in health and nutrition

Climate change has the potential to affect different diseases, including respiratory illness and diarrhoea. Disease results in a reduced ability to absorb nutrients from food and increases the nutritional requirements of people who are ill. Poor health in a community also leads
to a loss of labour productivity.

Further information Climate Change and Hunger: Responding to the challenge

Download the PDF  Food insecurity and climate change (PDF, 1 MB)