| Reforestation in the Pacific Islands |
Food and Fodder--Agroforestry
The natural forest provides an abundance of food resources to both people and animals. Since settlement and cultivation of forest land areas began, people have learned to use the forest in various ways, including the application of agroforestry, in which both food crops and trees are grown on the same land for a variety of end uses. More recently, the concept of agroforestry has gained greater attention as a means of alleviating some of the pressure for tillable land and protecting forest and land resources. (See Domingo, 1981; 1980; Spurgeon, 1979; King, 1979a; Douglas and Hart, 1976; Stewart, 1981; and Adeyoju, 1980.) Agroforestry is an integrated cropping system in which a mix of outputs may be produced on a continuing, sustainable basis. These products may be roughly divided into food and fodder outputs from both tree and agricultural crop cultivation, and wood products from the trees.
Fuel for cooking, lighting, and heating is extremely important to the upland farmer. In most areas wood is the cheapest, most familiar, and most easily available form of fuel. Fuelwood for use on upland farms--fallen limbs and branches and dead trees-- is usually collected from forested areas. In some regions, the forest areas have been destroyed or have receded so that the time and effort required for collection and preparation of wood for domestic use has become excessive. The shortage is so extreme in some areas that people are forced to cut down productive trees for use as fuel.
In agroforestry projects where the major products are food and fuel, the species may differ, but the basic techniques for cultivation and planting are similar to those in cropproducing agroforestry systems. The specific techniques for each type of agroforestry project are covered in Chapter 7.
In addition to its use as a domestic fuel, wood may also be in demand for commercial uses: wood chips used as a boiler fuel in place of gas or oil for steam production or electric power generation; production of chemicals or liquid fuels through fermentation or gasification; or small-scale commercial fuelwood or charcoal production for outside (usually urban) markets. Commercial fuelwood production may take place in a large corporate operation or may be practiced by small farmers, and may be part of monoculture or intercropped agroforestry systems. This manual is primarily concerned with the considerations for small-scale agroforestry systems.
In upland areas, timber is used for construction of poles and fencing and for other farm purposes. Timber may also be in demand where markets for pulpwood and electrical transmission posts exist. High-quality timber is also a major export item for many Pacific countries.
Environmental Benefits of Forests
As mentioned earlier, intensive cutting of forests and cultivation of marginal lands has resulted in rapid soil erosion and decline in productivity in many areas. Under certain conditions, erosion and declines in productivity can be effectively controlled through proven methods of forest farming. Besides requiring low inputs, forest farming techniques that utilize specific plant species can stabilize soils on sloping lands, help maintain and improve soil fertility, and positively impact the microclimate of an impacted area.
Particular tree and plant species, having deeper, more extensive root systems than other species, function to hold down soil on lands and reduce its tendency to erode when impacted by water and wind. This protective characteristic is enhanced when planted on sloping lands.
Tree and plant litter, consisting of leaves, branches, etc., also serve as ground cover, protecting the soil surface from the pounding of heavy rains and consequent splasherosion. The organic matter, together with the root system which penetrates into deeper subsoil, increases water filtration and absorption of water through the soil. This is particularly important during times of heavy rainfall (see Illus. 1-2).
By increasing soil stability, trees and plant cover may also prevent the damaging effects of siltation on streams and other water supplies, including irrigation channels, that may be caused by movements of large masses of soil.
Extremes in water levels--very low levels or flooding--may also be regulated with proper forest management. Well planned placement of vegetation may also serve as an effective windbreak, reducing wind erosion and damage to crops.
Both the tree and plant foliage, which serve as a windbreak and canopy, and "mulch" created by tree litter, provide shading and thermoregulation (temperature regulation) by reducing direct solar radiation upon the soil surface and moderating the water flow, thus regulating moisture content of soil. By reducing sunlight, the effects of high temperatures--such as hardening or "baking" of the soil surface, which causes impenetrability, and increases in evaporation of surface water--are reduced. By maintaining the temperature balance at the soil surface, the microclimatic conditions for decomposition of organic matter and release of soil nutrients are improved. The forestry canopy also protects the microclimate from drastic fluctuations between day and night temperatures. A full or partial canopy will also ensure the viability and productivity of light intolerant plant species. Because coffee trees are an understory plant, under certain conditions productivity is increased when grown under other tree species. Leafy vegetables are also sensitive to strong sunlight. Proper shading can extend their growing season.
The natural forests provide many other non-economic benefits that are sometimes difficult to measure and not always recognized by individual farmers or policy-makers.
• Forests, through their photosynthetic and filtering actions, provide a natural source of oxygen and pollution control.
• Wildlife habitat is another important forest product.
• The diversity of plant species in the forest and their spatial arrangements can deter insect proliferation. Careful study of these species and their interrelationships may provide important lessons for farmers and agronomists.
• As stated, 50 percent of the world's medicines come from natural plants.
• Plant species are also a source of aesthetic and recreational pleasure, and can serve as a "classroom" for important environmental education work.
The primary reasons for implementing forestry programs and projects are as follows:
• Conservation and protection of land quality, species diversity, and natural habitats for economic and non-economic benefit.
• Increase of productivity to develop economic and food production potential.
The type of project chosen and the species selected for forestry projects depend upon the specific conditions and needs of the project area. In the following chapters, we will discuss how the community forester can help to determine these needs.