What could threaten food security?
Vulnerable areas will be less resilient to the effects of climate change, but the repercussions will differ between regions.
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.
On average an increase in global precipitation is expected, but the regional patterns of rainfall will vary: some areas will have more rainfall, others less. There is still 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.
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 extended growing season observed in mid to high latitudes.
Carbon dioxide fertilisation:
The effect of CO2 fertilisation on crop growth is highly uncertain. In particular, there is a 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.
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.
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 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.
For many regions in the Tropics, a large portion of 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.
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.
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.