Previous - Next
3.5 Land degradation and woodland management
3.5.1 Characteristics of woodlands in dry areas
Woodlands in dry areas are drought-resistant in general and well adapted to the local ecological conditions where prevail low rainfall and high evaporation and to irregular distribution of rainfall. They are also adapted to recurrent drought.
These woodlands constitute a fundamental natural resource which transform solar energy into biomass and which protect and stabilize the soil surface. Under natural conditions and through sound management, forest ecosystems in dry areas maintain a balanced exchange of water and energy and conserve their equilibrium. Their exploitation by man induces a certain disturbance in their structure, but they could regenerate and reconstitute their equilibrium after the cessation of the disturbance. A continuous overexploitation of these woodlands provokes however a gradual deterioration and degradation which lead to the collapse of the ecosystem leading to desertification.
Dry forest ecosystems disturbed by land uses or stressed by drought, will usually return to what they were. Recover! tends to advance at a slow pace because of the low inherent fertility and productivity of the environment and is usually episodic, with more rapid recovery in years with above-average rainfall. Eventually, former water and energy balances will be restored, with the recovery of the original vegetation. This is a measure of the natural resilience of these dry woodlands.
In the sudano-sahelian zone, it has been observed that despite harsh climatic conditions and the repeated bush fires and fellings, a relatively short fallow period is sufficient for regeneration to start through seed germination, shoots and suckers, the latter representing an effective resistance tool.
The drylands plant cover often degrades by a succession of phases manifested by the replacement of the original woodlands by plant communities more and more xerophytic, and of low economic value and of little benefit for soil protection and conservation. At the advanced stage of degradation the plant cover disappears.
Soil degradation follows the plant cover destruction by loss of organic matter, destruction of the structure through water and wind erosion. The soil environment becomes more and more arid.
Where pressure of land use persists through drought, the woodlands in dry areas are shown to be too fragile in certain ecological conditions and processes can be set in motion whereby degradation becomes self-accelerating. This can occur where sand dunes are stripped of their woody vegetation, as near watering points or other places where stock tend to congregate; drifting sands then destroy more vegetation including less damaged woodlands and cover increasing surfaces through the process.
3.5.2 Causes of woodland degradation
The causes of woodlands degradation in dry areas are numerous and linked to the multiple services woody plant communities are rendering under these conditions: expansion in cultivated area, pasture, overgrazing, overcutting for fuelwood or charcoal, fire, etc.
Expansion in cultivated area is perhaps the greatest cause of deforestation in the dry tropical areas. The woodlands are threatened by excessive cutting and sluggish programmes of replacement. The rate of deforestation is around 8.5 to 10 times the rate of planting. The depletion of woodlands results from excessive population pressure and poor management of forest-society relationship.
The most frequently cited reason for deforestation was expansion in cultivated area. The demands for domestic firewood or charcoal are also mentioned as responsible of large areas of woodland degradation. The urban demand usually for charcoal leads to the wholesale cutting of woodlands. The commodity status of charcoal makes it an attractive choice for entrepreneurs who can derive incomes from its production and distribution and for this reason the high demand in certain cases could lead to overcutting.
Forest fires can also be responsible of woodland degradation in dry lands because they clear up the woody vegetation, destroy the natural regeneration and young trees, kill the aged trees and lead to the constitution of simplified stands. They lead also to the accumulation of dead trees and intensify the concentration of animals which lead to the degradation of the vegetation by overgrazing in the unburned zones. In the Sahel, forest fires constitute a main factor of desertification.
In the Near East, deforestation is mainly due to the expansion of the cultivated lands and to forest fires. Large areas of woodlands in the dry subhumid and the upper semiarid zones have been cleared illegally for fruit tree plantations in sloping areas, without taking any conservative measures to prevent water erosion.
The woodlands in the dry areas of the Mediterranean region are subject to serious degradation, especially in the eastern and southern part of it, but there are no statistics for the loss of forest lands and for the degree of degradation of these woodlands.
3.5.3 Present situation of the woodland degradation
According to FAO Forest Resources Assessment, 1990, the forest cover in West Sahelian Africa was 43.7 million ha at the end of 1980 and 40.8 million ha at the end of 1990 with a loss of 0.3 million ha (0.7% per annum) and in East Sahelian Africa, 71.4 million ha at the end of 1980 and 65.5 million ha at the end of 1990, with a loss of 0.6 million ha (0.9% per annum, and in Tropical South Africa, 159.3 million ha at the end of 1980 and 145.9 million ha at the end of 1990, with a loss of 1.3 million ha (0.9% per annum). In the dry and very dry zone of the whole tropical world, the annual deforestation during 1981-1990 was 2.2 million ha (0.9 % per annum).
3.5.4 Consequences of deforestation in drylands
Woodlands in dry areas represent a stock of biomass of multiple use for the people in the drylands and constitute a major source of useful genetic materials for agriculture, medicine and other pharmaceutical products. The ecological services that woodlands in dry areas provide are many and difficult to assess in terms of money.
The deforestation in drylands leads to increased water erosion with an indirect impact on water resource development, depletion of soil fertility, disappearance of many plant and animal species, local acidification, etc. In addition, flooding, accelerated runoff, droughts, more sedimentation in rivers and reservoirs and depleted groundwater become more severe because of deforestation, with the adverse consequences for agricultural production and human life. Wind erosion takes place in the denuded dry plain engendering dust.
Deforestation often but not always, leads to environmental degradation in the sense of loss of land productivity. The extent; of degradation, if any, depends on the use to which the cleared lands are put and its subsequent management. Forest land was often successfully converted to stable agro-sylvo-pastoral systems which brought high returns. Moreover, there were also cases of unplanned and inappropriate land use, such as slash-and-burn practices which did not allow sufficient time for regeneration. Such degradation was not necessarily related to population pressure and poverty, but was due in a large extent to the absence of sound land use planning and supporting policies, or the lack of physical and institutional infrastructure, necessary for economic exploitation of the cleared lands.
3.5.5 Development of forestry resources in dry areas
a. Many national forestry departments are still predominantly concerned with traditional forestry plantations for supplying firewood, building materials, etc. Few resources are devoted to rural afforestation, soil and water conservation and indigenous woodlands. Agricultural services mostly ignore the important role of trees in peasant farming systems both from a biological and economic point of view.
Problems of environmental degradation, deforestation, fuelwood supply in drylands cannot be solved by tree planting alone. What is needed is a holistic approach to agriculture, livestock, land settlement, forestry and energy policies. Forestry could play an important role in this approach if it is included in integrated rural development aiming at the improvement of the welfare of rural people and at the protection of the environment.
For this reason, forest plantations in arid and semi-arid zones may have little beneficial effects unless they are closely related to the needs and priorities of the people living there. Thus, the integration of trees into the farming systems should arise from the objective not only of growing trees but of improving the rural families welfare, which involve, among other things, the introduction of some form of woody vegetation with multipurpose use: firewood, fruit, honey, gum, tannin, pharmaceutical products, etc., which is accepted by the farmers in order to take care of it and consider it as an important component of the system. The most promising means of encouraging the practice of arid land forestry for multipurpose use appear in planting multipurpose shrub and trees in cultivating lands, in rehabilitating degraded rangelands, in soil and water conservation, in watershed management. Understood in this manner, forestry will play an important role in achieving sustainable development in arid. semi-arid and dry subhumid areas.
b. Forestry will then play a crucial role in contributing feed for livestock and supplementing the diet of the rural populations, both directly in the form of fruits, nuts and leaves, and indirectly through honey and wildlife. Opportunities to benefit from this role of forestry need to be explored through an expanded programme of agro-forestry adapted to different climates and farming systems and of wildlife management. Agroforestry should be seen as an integral part of future drylands development in the semi-arid zone where it is relatively easy to establish trees and shrubs and promote full fledged forest food, fuel and fodder systems.
Training of foresters and technicians in drylands should cover agroforestry and wildlife, and training institutes should include programmes relevant to particular needs of drylands.
c. Experience shows in various arid lands of the world that forestry can neither develop nor survive without active involvement of the local community, hence community participation is one of the most important ingredients of forest development.
d. The scope of national forest policy should accord special emphasis to the role of woodlands and trees and shrubs in dry areas in providing support services to agriculture, contributing to appropriate agroforestry systems, specifically promoting the welfare of the rural poor, contributing to the fuel and energy needs of both rural and urban people and rehabilitating marginal land. Special attention should be paid to the involvement of women working in agriculture. Our endeavour should turn these working women into growers of trees, instead of mere collector. Women extension workers could help in the use of more efficient fuel stores or alternative energy sources such as solar cookers and to encourage local manufacture as an additional local industry. Legislation facilitating community forestry activities should be available in every country in order to carry out effectively extension programmes and developing forestry under its different aspects in drylands.