TROPICAL FORESTRY

In the past, timber harvest in the Tropics has seldom been followed by regeneration. Conversion to agriculture is often permanent or results in soil erosion. Timber harvest contracts have usually been short term and have provided little or no incentive for timber companies to replant. So little reforestation has been done in the Tropics that many people believe these forests cannot be restored. However, there are many examples of successful reforestation in India, Indonesia, and the Caribbean.
In the Tropics, as elsewhere, forestry is a mixture of modern innovations and ancient techniques borrowed from local tradition. Plantation forestry is common. Forest reserves have been established for timber harvest, wildlife habitat, scenery, outdoor recreation, or watershed protection. And in the Tropics, agroforestry-tree growing combined with agricultural cropping-is much more common than elsewhere.

Plantation Forestry
In the Tropics, trees are often planted and grown in plantations for wood production. Often, many species must be tried to determine which will grow best. Plantations must also be supported by major investments in forest management and research. Forest nurseries must be established, and planting techniques and cultural practices (spacing and thinning, pruning, fertilization, insect and disease control, and genetic improvement) must be developed.
Extensive pine plantations have been established in the moist Tropics, mainly in South Africa and Australia. Species most often planted include Caribbean pine (Pinus caribaea), ocote pine (P. oocarpa), slash pine (P. elliottii), and benguet pine (P. kesiya). Pines are popular plantation trees because they are generally fast growing, have good survival rates, and are adapted to a wide variety of environments, including degraded forest sites.
Eucalypts, including species such as Eucalyptus grandis, E. deglupta, E. tereticornis, E. globulus, and E. camaldulensis are favored for the same reasons. Eucalypts are commonly grown for pulp, fuel, and lumber. Other species commonly planted include teak (Tectona grandis), Honduras mahogany (Swietenia macrophylla), melina (Gmelina arborea) beefwood (Casuarina equisetifolia), and Mexican cypress (Cupressus lusitanica).

Forest Reserves
There are many reasons for establishing forest reserves in the Tropics. They can restore watersheds and wildlife habitat, improve scenic beauty and opportunities for outdoor recreation, and produce wood and other products for local use and export. Many forest products contribute to the sustenance and income of local people: wildlife and fish, firewood, rubber, fruits and nuts, rattan, medicinal herbs, floral greenery, and charcoal.
Perhaps the most famous of these reserves is the 5,600 square mile (14,500 k squared) Serengeti National Park in Tanzania. With its vast herds of grazing ungulates (hoofed animals) and predators, including several endangered species, the Serengeti is a showcase of a savanna ecosystem that has long been protected and managed for wildlife and other natural resources. Although plagued with poachers, the Serengeti promotes the cause of wildlife conservation to the many thousands of "ecotourists" who pay to experience nature each year.
Another type of forest reserve is the "extractive" reserve, which is dedicated to the production of useful products. Large reserves of this type have been established recently in Brazil. Local residents use them for tapping rubber, for gathering fruits and nuts, for hunting, and for harvesting wood on a sustained yield basis. Such uses provide a sustainable income while maintaining the ecological integrity of the forest.

Agroforestry
The practice growing of trees in combination with agricultural crops is fairly common in the Tropics. It is possible to grow food crops year around in many forested areas, and rural poor depend on this source of food as nowhere else on Earth.
Taungya System
Various systems have been developed for combining forestry with agriculture. "Taungya" is a Burmese word meaning cultivated hill plot. This system of agroforestry was developed in Europe during the Middle Ages and probably indepenently in a number of places in the Tropics. After existing forest or ground cover is removed by burning, trees are planted along with agricultural crops. Both are cultivated until the tree canopy closes. Then the area is left to grow trees, and another site is located for combined forestry agriculture.
Shade Cropping
An overstory of trees is often used to provide shade for agricultural crops. A common practice is to grow tree species such as guaba Inga vera) over coffee. In Puerto Rico, many forests developed where coffee was once grown in this manner.
Support Crops
Trees can be planted to provide support (and sometimes shade) for vine crops. Vines such as pepper and vanilla need support.
Alley Cropping
Nitrogen-fixing trees are planted in hedges in widely-space parallel rows along the contour of slopes. Food crops are grown in the "alley" between the rows. The trees add nitrogen and organic matter, protect the soil from erosion, and provide wood and animal forage.
Living Fences
Green fenceposts that will root and sprout often are planted in a closely spaced row. When they sprout, they create a "living fence" that provides shade and forage for cattle.

Windbreaks
Trees are often planted as windbreaks for agricultural crops, farms, or homesites. Such plantings can eventually contribute wood products as well as shelter. Food trees such as citrus, rubber, and mango can also provide fuel, lumber, and other wood products when they have outlived their original usefulness.

NEW DIRECTIONS IN TROPICAL FORESTRY
The conservation issues of the past seem simple compared with those of today. As we move toward the 21st century, human societies are concerned with global warming, deforestation, species extinction, and rising expectations. Growing populations must be fed, clothed, and sheltered, and people everywhere want higher standards of living.
Global Warming
Warming of the earth's atmosphere is a major environmental issue. Air pollution, deforestation, and widespread burning of coal, oil, and natural gas have increased atmospheric concentrations of carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons. These gases trap heat from the sun and prevent it from radiating harmlessly back into space. Thus, the 64 greenhouse" or warming effect is created.
Because of natural variations in climate, it is difficult to measure warming over large areas. Scientists agree, however, that increases in atmospheric concentrations of greenhouse gases will cause higher temperatures worldwide. Even an increase of a few degrees might cause serious melting of the polar icecaps, a gradual rise in sea level, a disruption in normal weather patterns, a possible increase in forest fires, and the extinction of species.
Role of Forests
Trees, the largest of all land plants, act as a kind of environmental "buffer" for the ecosystem they dominate. They help ameliorate the extremes of climate (heat, cold, and wind) and create an environment where large land mammals, including people, can live comfortably. Trees complement animals in the global environment. Mammals take in oxygen from the air and exhale carbon dioxide. Plants use the carbon dioxide in their growth processes, store the carbon in woody tissues, and return oxygen to the atmosphere as a waste product. This process, known as photosynthesis, is essential to life. Carbon captured from the atmosphere by photosynthesis is eventually recycled through the environment in a process known as the carbon cycle. Trees have an especially important role in the carbon cycle. Tree leaves also act as filters to remove atmospheric pollutants from the air. This effect is particularly beneficial in urban areas.

Forestry Issues
Two key issues will dominate forestry in the years ahead: (1) maintaining long-term productivity of managed forests, and (2) preventing further loss of tropical forests. Both problems will require new approaches to forest management.
Traditionally, forestry has focused on growing crops of wood in plantations or in managed natural stands. In this "agricultural mode," other benefits of forest such as watershed protection, wildlife habitat, climate moderation, and outdoor recreation, have received less attention than wood production.
Perhaps more importantly, the sustainability of the full range of forest benefits has not been measured. There is no question that trees can be grown for crops of wood in managed stands. With intensive management-short rotations, species selection, genetic improvement, fertilization, thinning, and other cultural treatments-more wood can be produced in less time than in natural forests. But for how long? And at what cost in other benefits?
As more and more of the world's original forests have been cut, the ecological value of forests has come to be more appreciated. In recent years, increased emphasis has been put on what some are calling "ecosystem management." In this model, the health and long-term stability of the forest are paramount, and timber production is considered a byproduct of good forest management rather than the principal product. In Puerto Rico, for example, wood production is a relatively minor aspect of forestry.
Since the 1930's when timber harvests were curtailed, the forests have been managed primarily for watershed protection, wildlife habitat, and outdoor recreation.
There are no easy solutions to the problem of tropical forest destruction, but most experts agree that the problems cannot be solved simply by locking up the forests in reserves. The forests are too important to local people for that to be a workable solution. There is no doubt that tropical forests will be cut. It is better for them to be cut in an ecologically sound manner than to be cleared for poor-quality farmland or wasted by poor harvest practices.
The only real long-term solutions are: (1) more efficient agriculture on suitable farmland, (2) efficient forestry practice including plantations, and (3) reserves to protect species and ecosystems. Many forestry experts believe that we have only begun to tap the potential for wise use of tropical forests. Many uses have yet to be fully explored. We are only starting to learn the value of tropical forests for medicines, house and garden plants, food and fiber, tourism, and natural resource education.
A Student Guide To Tropical Forest Conservation