Climate Sense

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Climate change and food security

Richard A. Betts, Pete D. Falloon, Jemma Gornall, Neil Kaye and Andrew Wiltshire, Met Office Hadley Centre;

Timothy R. Wheeler, Walker Institute for Climate Systems Research, Department of Agriculture, University of Reading, UK

ood security has been defined as ‘a situation that exists

when all people, at all times, have physical, social and

economic access to sufficient, safe and nutritious food

that meets their dietary needs and food preferences for an active

and healthy life’.

Although the production of food is clearly

fundamental, the concept of food security goes beyond produc-

tion and considers the entire system. It therefore encompasses

other aspects of food availability such as distribution and

exchange, and wider issues of access and utilization.

Global food systems are inherently linked to climate in a large number

of complex ways. The productivity of food crops, livestock and

fisheries is highly dependent on climatic conditions and other envi-

ronmental factors linked to climate, such as atmospheric composition.

There is a tradition in agriculture of coping with year-to-year changes

in climate. Nevertheless, human-induced change is expected to push

these managed ecosystems beyond their natural boundaries, requiring

greater adaptation. Climate change and its drivers are therefore likely

to impact on the production aspect of food security. Moreover, since

social and economic systems as a whole are influenced by climate,

food security is also likely to be impacted by climate change through

its wider effects on infrastructure and economies.

Impacts of climate change on food production

Climate change is likely to directly impact on food production across

the globe. At higher latitudes where production is currently limited by

temperature, producers may benefit from longer growing seasons for

moderate warming, although higher levels would be expected to counter

these benefits. Even moderate levels may not necessarily confer benefits

without adaptation by producers, as an increase in the mean seasonal

temperature can bring forward the harvest time of current varieties of

many crops and hence reduce final yield, in the absence of any adapta-

tion to a longer growing season.

In areas where temperatures are already

close to the physiological maxima for crops, warming will impact yields

more immediately.

In seasonal arid environments higher temperatures

may also be more immediately detrimental by increasing heat stress on

crops and water loss by evaporation.

Changes in short-term temperature extremes can be critical, espe-

cially if these coincide with key stages of crop development. Only a

few days of extreme temperature (greater than 32°C) at the flower-

ing point of many crops can drastically reduce yield.

Temperature

extremes also increase the risk of heat stress to livestock. Changes in

the water cycle will be vital to production, whether by a decrease in the

availability of fresh water or increasing damage caused by an excess.

More frequent heat waves and droughts are expected,

causing yields

of food crops and fodder for livestock to be more variable from year to

year,

decreasing overall.

Further development of crop cultivars that

are more tolerant to extreme weather is needed. Other

impacts of drought may be reduced pasture productiv-

ity, increased livestock deaths, soil erosion via wind and

land degradation.

Food production can also be impacted by too much

water. Heavy rainfall events leading to flooding can

wipe out crops and drown livestock over wide areas,

and since an increase in the intensity of extreme rain-

fall is expected in a warmer world,

damaging flooding

events may become more frequent.

Flooding aside,

direct negative impacts of excess water include soil

water-logging, anaerobicity and reduced plant growth.

Indirect impacts include delayed farming operations

or implementation when they could cause compac-

tion damage, as in livestock treading and ‘poaching’.

Agricultural machinery may simply not be adapted

to wet soil conditions. Extreme wind events such as

intense storms and hurricanes can also cause wide-

spread damage across cropland areas.

Changes remote from production areas may also be

critical. Irrigated agricultural land comprises less than

one fifth of all cropped area but produces 40-45 per

cent of the world’s food,

and water for irrigation is

often extracted from rivers which depend on distant

climatic conditions. Some key rivers are fed by moun-

tain glaciers, with approximately one-sixth of the

world’s population currently living in glacier-fed river

basins. Populations are projected to rise significantly in

major glacier-fed basins such as the Indo-Gangetic plain

and other major irrigated areas such as those near the

Yangtze and Nile. As such, changes in remote rainfall

and the magnitude and seasonality of glacial meltwaters

could impact food production for many people.

Sea-level rise is another potential indirect influence.

In low-lying coastal areas, rising seas will inundate agri-

cultural lands and salinize groundwater. Short-lived

storm surges can also cause great devastation, even if

land is not permanently lost. These impacts will chal-

lenge the livelihoods of many millions of people who

live near the world’s mega deltas. Both marine and

freshwater fisheries may also be impacted by change.

Positive and negative impacts of warming on fish

have been reported.

Marine fisheries may be affected

by general poleward shifts in ranges determined by

temperature, and shifts in the ranges of pathogens and

changes in nutrient supply due to altered oceanic circu-

lation. Freshwater fisheries may benefit from increased

mpacts

and

mplications

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