How global warming affects the weather
It seems that everybody has now heard about “global warming” or “climate change.” The weather is changing and the earth is getting warmer because human actions – such as burning coal, oil and gas for energy – are increasing the levels of “greenhouse gases” in the earth’s atmosphere. These gases, which include carbon dioxide, methane and nitrous oxide, stop some of the sun’s heat from reflecting back into space. Heat is trapped in the earth’s atmosphere, which increases the temperature on the surface of the earth. Because of the increase in greenhouse gases in the atmosphere, global average temperatures are predicted to rise between 1.5 and 4 degrees by the year 2100. This may not sound like much, but together with changes in rainfall, it will have a large impact on farmers.
As the temperature rises, the weather will be affected in different ways all over the planet. Drought is likely to get worse in some areas, especially in the African grasslands, where rainfall is expected to decrease and become more unpredictable from year to year. The rising temperature will also cause soil, lake and river moisture to evaporate more quickly from the surface of the earth. As the soil become drier, it may be more difficult to grow crops which need a good amount of moisture, such as maize.
In other areas, especially coastal regions, higher temperatures will be accompanied by higher rainfall. Coastal lands and small islands will be at risk from rising sea levels and more intense storms. For example, Lagos and the cities in the Niger delta would be affected. Coastal agriculture such as the palm oil and coconut plantations in Benin and Côte d’Ivoire could be at risk of flooding, as could crops along the Kenyan coast.
How will global warming affect local agriculture?
We’ve already mentioned how an important crop like maize might be more difficult to grow as a result of global warming. Other crops will be affected, especially in tropical and subtropical areas. Yield decreases are likely because:
1) Many varieties of rice may not set grain if temperatures become hotter, and
2) There will be less water for crops if rainfall decreases and evaporation increases.
Food production will also be affected by:
- an increase in the frequency of extreme weather such as storms, floods and droughts,
- longer growing seasons in very cool areas,
- dramatic changes in the distribution and quantities of fish and seafood, and
- possible increases in pests and diseases.
The following are some of the potential impacts of global warming in Africa.
- Increased droughts could seriously reduce the amount of food available.
- Millet yields may decline by 63%-79%.
- Yields of freshwater fish may increase, although the mix of fish species could be altered. While some fish species will fare better at increased temperatures, other species are not as well adapted to higher temperatures, and their numbers are likely to decrease.
- Tsetse fly infestations could expand into more southerly areas of Zimbabwe and Mozambique, move westward in Angola, and northeast in Tanzania. At the same time, their numbers may decrease in some of the areas where they currently exist.
What can farmers do?
Farmers in your audience probably already use effective methods to limit damage from weather. You can encourage them to do more of this damage control, and to adapt and improve their methods. For example, both soil and water degradation are likely to worsen with global warming. So methods to conserve soil and water will be particularly useful.
When you are preparing your radio program, talk to local experts (research stations, national weather services, universities, and your country’s FAO office) to find out how climate change is likely to affect your region. Then you can share strategies that may be useful for the farmers who listen to your program. Talk to farmers and get their feedback on whether these strategies are suitable for their area. You might want to refer to past Farm Radio International scripts. We have noted some scripts that could be helpful.
1. If your area is vulnerable to storms, hurricanes, typhoons and floods:
- Plant trees (for example, mangroves) to protect coastal regions from flooding and erosion.
- Plant crops that are least vulnerable to strong winds. Root crops are a good choice. (See script 58.11 – Grow and eat nutritious yams)
- Avoid using slash and burn methods to clear land.
- Avoid planting temporary crops on steep slopes. (See script 44.9 – Save soil on sloping land)
- Establish tree and grass barriers to stop erosion. (See script 43.3 – Prevent erosion with vetiver grass)
- Keep land covered with vegetation or mulch at all times. (See scripts: 34.1 – More with mulch; 50.4 – Farmers in Nicaragua challenge El Nino; 58.5 – Grow your own fertilizer by planting cover crops with maize; 64.2 – Soil conservation saves the land, even when a hurricane strikes);
- Use recommended planting material to establish windbreaks. (See script 44.2 – Windbreaks protect crops and soil)
- Make good use of indigenous knowledge (See script 60.3 – A local farmer predicts floods)
- Make plans for coping with disaster (See script 64.10 – Disaster prevention, mitigation and recovery: story ideas for the radio)
Protecting coastal regions with mangrove plantations: An example from Asia
Typhoons strike the coast of Vietnam eight to ten times per year. They often break sea dikes and destroy aquaculture farms. To provide a barrier in front of the dikes, and protect coastal land, the Vietnam Red Cross established 2000 hectares of mangrove trees. The mangrove plantations are also used to harvest and market valuable sea products such as shrimp, crabs, and cultured seaweed. Shortly after completion, the mangrove plantation was hit by the worst typhoon in a decade. But there was no significant damage to the dike and aquaculture pond systems.
2. If your area is at risk from drought, desertification, and soil and water degradation:
In drier areas, it is predicted that lower rainfall and higher evaporation rates will degrade soil and water, and hasten the process of desertification. Farmers will need to practise soil and water conservation. They can:
- Capture and store runoff water. (See scripts: 54.3 – Garden while you shower; 54.7 – Catch rain from your roof)
- Use tillage methods that conserve soil and water, and limit erosion. (See scripts: 50.7 – Stop soil erosion with living plant barriers; 55.9 – Trees and terraces prevent hillside flooding; 50.2 – Farming for the future, some practical methods)
- Add organic matter to the soil, such as crop residues, compost, and manure. (See scripts: 33.9 – Where to find compost materials; 47.8 – Make something with nothing in a rubbish garden; 61.6 – Dr. Compost talks about compost piles)
- Plant legumes to help fertilize the soil. (See script 80.8 – Legumes Make Their Own Fertilizer – With Help from their Friends)
- Keep the soil covered with vegetation at all times. Use cover crops. (See script 58.2 – Improve rice yields without buying fertilizer)
- Practise agroforestry. (See scripts: 55.7 – A farmer turns wasteland into rainforest; 55.1 – Choose the right trees to grow with crops; 54.1 – Trees and rain; 54.2 – How trees store water and protect springs; 58.4 – Growing maize with trees; 27.2 – Trees in your garden give you fertilizer; 88.7 – Farmers in Niger benefit from letting trees grow in their fields;78.6 – Community Reforestation Brings Back the Rains in the Brong Ahafo Region of Ghana;74.3 – “When it rains” The Role of Trees in Preventing Soil Erosion; 68.3 Rehabilitating degraded land: planting trees in pits)
- Dig planting pits in dry areas. (See scripts: 54.5 – Infiltration pits catch water for crops;64.6 – Farmer Phiri uses infiltration pits to combat drought)
- Plant drought-tolerant crops and crop varieties. (See scripts: 54.9 – These crops will help you through the drought; 73.3 – Choosing crops for drought-prone areas)
- Choose and experiment with effective, long-term storage techniques. (See scripts: 48.10 – Use hot peppers to protect stored grain; 79.8 Storing cowpeas for a season and a reason)
Improving techniques for long term storage
To store crops for longer periods of time, farmers in Sudan have modified the matmura, their traditional sorghum storage pit. Traditionally, farmers poured sorghum into the matmura pits until a dome shape was formed. Then they would add a layer of chaff on top. The pits were one and a half metres deep. But now farmers make shallower pits, about 50 centimetres deep. This keeps the grain drier for two reasons. First, it reduces leakage through cracks. Second, less moisture gets into the grain. With less moisture, there are fewer insects, which improves the quality of the grain. Farmers have also increased the amount of chaff that they place on top of the sorghum. Now the layer of chaff is 50 centimetres deep and extends for about one metre around the filled pits. These new innovations have increased the safe storage period.
3. If you live in a cooler area:
In cooler areas, the growing season may become one month longer, or more. Here are some methods to discuss on your program:
- Test and select crop and crop varieties most suitable for the newly extended season.
- Plant earlier in the season.
- Grow a second short-season vegetable crop when possible. (See script 53.10 – Intercropping: radio spots)
- Plant heat-resistant varieties of wheat and other crops.
4. If rainfall in your area will be more uncertain:
Effective and long-lasting crop storage is going to be more important than ever. Also, you could advise farmers to:
- Harvest rainwater and runoff water. (See scripts: 44.3 – Cross ridging holds precious rainwater on the land; 54.7 – Catch rain from your roof ;61.4 – Farmers and scientists harvest rainwater in India ; 76.9 – A woman harvests water and grows vegetables in the dry season; 71.8 – Harvesting water using earth banks)
- Plant drought-tolerant crops and crop varieties. (See script 58.7 – The advantages of growing and using finger millet; 58.10 – My friend the dependable sweet potato)
- Use soil and water conservation methods. (See script 43.5 – A woman farmer fallows with trees; 54.5 – Infiltration pits catch water for crops)
- Practice soil and water conservation methods. (See script 84.11 – Farmers can prepare for changing weather patterns)
An example of harvesting surface water
Several kinds of planting pits can be used to harvest surface water. One kind is the zai hole. Zai holes are a traditional method of catching and holding runoff water. They are used in soils that are so badly degraded that water cannot penetrate.
During the dry season, farmers dig a hole that measures 20 x 20 centimetres to a depth of ten centimetres. The hole is filled with crop residues or manure. These materials attract termites, which make holes in the pit. The termite holes increase the amount of water that can penetrate the soil when the rains come. Millet and other crops are planted in the zai holes. In Burkina Faso, farmers using this method have improved their yields several times over. The zai holes also protect seedlings from strong winds. Even when rainfall is much lower than normal, zai holes have worked well in most cases.
5. Growing different crop species and raising different animals
In many areas, farmers may benefit from planting different crops and raising different kinds of livestock, or changing plant varieties and livestock breeds to address the new farming conditions they will encounter.
On your program, you could discuss how to select new or alternative crops, or crop varieties. Here are some ideas:
- Grow salt-tolerant crops or varieties if soil becomes contaminated with salt.
- Grow drought- and heat-tolerant crops in areas where drought and heat increase with climate change. (See scripts: 58.7 – The advantages of growing and using finger millet; 76.10 – Mangoes can be a good investment for farmers in drylands; 82.6 – Fonio)
- Consider raising small livestock. See scripts: 80.1 and 80.2 Raising rabbits for meat and profit, parts one and two; 80.6 – Raising snails for food and profit)
- Grow cassava where rains are uncertain, because it can be stored in soil for a long time before being harvested.
- Grow short rice cultivars in areas where strong winds are a problem, because they are more resistant to winds.
- Plant rice and other crops earlier in the year in areas where higher temperatures are the major problem. When rice flowers during the hottest time of the year, it can be killed.
- Another strategy is to plant varieties which flower early in the morning, thus avoiding the hottest time of day.
Contributed by: Vijay Cuddeford, managing editor, Farm Radio International.
Reviewed by: John Stone, Adjunct Research Professor, Carleton University.
Boko, M., I. Niang, A. Nyong, C. Vogel, A. Githeko, M. Medany, B. Osman-Elasha, R. Tabo and P. Yanda, 2007: Africa (chapter on). Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge UK, 433-467. http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter9.pdf
FAO, undated. Some effects of global warming on agriculture. Food and Agriculture Organization of the United Nations (FAO). Fax: +39.06.570.53023. http://www.fao.org/english/newsroom/factfile/IMG/FF9721-e.pdf
Laura S. Meitzner and Martin L. Price, 1996. From Amaranth to Zai Holes: Ideas for Growing Food Under Difficult Conditions. Educational Concerns for Hunger Organization. ECHO, 17391 Durrance Road, North Fort Myers FL 33917-2239, USA. Tel: (941) 543-3246, Fax: (941) 543-5317. E-mail: ECHO@echonet.org. http://www.echotech.org/technical/az/aztext/azcntnts.htm
Nageeb Ibrahim Bakheit, Kees Stigter and Ahmed el-Tayeb Abdalla, 2001. Underground storage of sorghum as a banking alternative. ILEIA, Volume 17, Number 1, April 2001. http://www.ileia.org/index.php?url=getblob.php&o_id=12467&a_id=211&a_seq=0