16. Living fences. A close-up look at an agroforestry technology.
Agroforestry Today, 2, No. 3, 1990, pp. 11-13
Living fences are lines of trees or shrubs planted on farm boundaries or on the borders of home compounds, pastures, fields or animal enclosures.
Their mean purpose is to control the movement of animals or people. This purpose is what differentiates them from other agroforestry technologies based on trees planted in lines, such as boundary plantings, contour strips or hedgerow intercropping. Besides their main function to control human and animal movement living fences may provide fuelwood, fodder and food, act as windbreaks or enrich the soil, depending on the species used.
In Central America many farmers adopted living fences. The reasons are:
- Increasing population, decreasing farmland, and declining food subsidies were forcing more intensive agricultural production.
Living fences/hedges are permanent, densely spaced, single or multiple lines of woody plants. They are regularly pollarded and trimmed.
Live fenceposts are permanent, widely spaced, single lines of woody plants that are regularly pollarded. They are used to support wire or other inanimate material, such as sticks or dead branches.
Living fences/hedges may be thicker than live fenceposts and may comprise more than one species, including trees, shrubs and smaller plants. They usually do not include wire or other inanimate material.
Farmers in Costa Rica and Honduras supplement their incomes by selling branches from their live fenceposts to neighbours wishing to establish new fences.
Many different tree species are used for living fences, depending on the ecological zone, the availability of stock and the specific needs of farmers. The most common species in Central America, northern south America and several Caribbean countries are Gliricidia sepium, Bursera simaruba, Spondias purpurea and Erythrina berteoana.
Living fences of G. sepium and Erythrina spp. are harvested to provide fodder for cattle, goats, rabbits and chickens (providing up to 25% of total intake), and the thicker branches of Gliricidia are used for fuelwood. Edible fruits and flowers can also be important, for example the 'jacote' fruit of S. purpurea, which is sold in markets in many Central American countries.
Living fences are a familiar feature throughout much of the African landscape. They appear on the densely populated hillsides of western Cameroon and in Rwanda and Burundi, marking small cultivated plots. In the dry rangelands of Northern Africa and the Sahel they form livestock enclosures and pathways to protect croplands and pasture from moving animals.
Species used for living fences in Africa include plants with good natural defence systems, such as long thorns, spines or unpalatability.
Examples are Dovyalis caffra (kei apple), Agave sisalana (sisal) and Euphorbia spp. Depending on site conditions and available plant material, a variety of other woody species may be used, including Ziziphus mauritiana, Z. mucronata, Commiphora africana, Erythrina abyssinica and Gliricidia sepium.
As the trees and shrubs grow, they must be pruned, usually on an annual basis. Otherwise, they may take up too much space or cast too much shade on adjacent crops. Root competition may also be a problem.
Well-established living fences may be difficult and expensive to remove, so they should be sited carefully before planting. If planted on a boundary, a living fence will affect more than one land user, so it is important that all land owners and users should agree on its establishment.
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Asia, Bangladesh, survey, evaluation, project, homestead agroforestry, land-use system, ICRAF
LEUSCHNER, W.A. and K. KHALEQUE
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