How does climate change affect agriculture?
Scientists have alerted global policy makers to the perils of climate change over the coming decades and it remains to be seen whether major international agreements can now be reached.
Agriculture is considered to be one of the most vulnerable sectors. The Declaration of the World Summit on Food from November 2009 stated: "Climate change poses additional severe risks to food security and the agriculture sector. Its expected impact is particularly fraught with danger for smallholder farmers in developing countries, notably the Least Developed Countries (LDCs), and for already vulnerable populations." In a newly published report the WTO and UNEP state that in low-latitude regions, even a small temperature increase of 1°C would lead to reductions of 5-10 percent in the yields of major cereal crops. By 2020, crop yields in African countries could fall by up to 50 percent.
Climate change has started to significantly affect agriculture and rural landscapes: In recent years both droughts and floods attributed to changing climatic conditions have been getting more pronounced. Rising temperatures are expected to bring crop-shrinking heat waves, melting glaciers and ice sheets, and rising sea levels, with major consequences for global food security.
Over the next 100 years, accelerated warming and expansion of water in the oceans, and increased melting rates of low-lying glaciers and ice caps are expected to increase sea levels by a metre or more. This will have major consequences for low-lying farmland across the world. For instance, a one metre sea level rise would affect half the rice land of Bangladesh. A two metre rise would inundate much of the Mekong Delta which produces half the rice in Vietnam, the world’s second most important rice exporter, etc.
The melting of mountain glaciers is another global threat. Already the snow caps on Mount Kenya and Kilimanjaro in east Africa have largely disappeared. The shrinking of glaciers in the Himalayas and on the Tibetan plateau is particularly alarming since they feed the Indus, Ganges, Yangtze, Yellow and Mekong Rivers on which the irrigation systems of hundreds of millions of Asian farmers depend. As a result, Asia’s rivers are likely to become ever more erratic or even cease to flow during the dry season.
Climate change will also affect the environmental services provided by major ecosystems, such as rainforest, impairing their crucial role in distributing rainfall over vast areas, whilst removing huge amounts of carbon from the atmosphere at the same time.
As greenhouse gas concentrations increase and temperatures rise, the frequency and intensity of extreme weather events such as cyclones, floods, droughts and heat waves may also change. Rising ocean temperatures, in particular, are expected to affect storm and cyclone development.
Across the world in the last few years, flooding and other extreme weather, attributed to climate change, is reaching new heights. For example:
- In 1995, half of Bhola Island, Bangladesh, became permanently flooded, leaving 500,000 people, mainly farmers, as the world's first climate refugees.
- Since 2001, much of the Murray-Darling Basin, Australia’s breadbasket, is experiencing the worst droughts for over 100 years. Storage levels will take many years of above average rainfall to recover.
- Threats to Uganda's coffee crop are threatening the country’s main export income.
- The UN is having to feed millions of people in Africa, and particularly Ethiopia and Kenya.
- Millions of people have been affected by major floods in South Asia.
- Increasingly erratic monsoons are causing major problems for farmers in India.
