A Student Guide To Tropical Forest Conservation

J.Louise Mastrantonio and John K. Francis

SUMMARY
The world's tropical forests, which circle the globe, are interestingly diverse. Ranging from the steamy jungles of the rain forests to the dry forests and savannas, they provide habitat for millions of species of plants and animals. Once covering some 15.3 billion acres (6.2 billion ha), these tropical forests have been reduced through cutting and clearing by 210 million acres (85 million ha) between 1985 and
1990. All types of tropical forests are defined and their products and benefits to the environment are presented and discussed. Modern forest practices are shown as a means of halting forest destruction while still providing valuable forest products and protecting and preserving the habitats of many endangered species of plants and wildlife. The Luquillo Experimental Forest is presented as a possible model to exemplify forestry practices and research that could manage and ultimately protect the tropical forests throughout the world.

INTRODUCTION
The world's tropical forests circle the globe in a ring around the Equator They are surprisingly diverse, ranging from lush rain forests to dry savannas and containing millions of species of plants and animals. Tropical forests once covered some 15.3 billion acres (6.2 billion ha). In recent times, however, they have been cut at a rapid rate to make room for agriculture and to obtain their many valuable products. Between 1985 and 1990, 210 million acres (85 million ha) of tropical forests were destroyed.
This guide shows how modern forest practices can help stem the tide of forest destruction while providing valuable forest products for people. The tropical forests of Puerto Rico, which were abused for centuries, were badly depleted by the early 1900's. Widespread abandonment of poor agricultural lands has allowed natural reforestation and planting programs to create a patchwork of private, Commonwealth, and Federal forests across the land. The most frequent example in this publication is the Luquillo Experimental Forest, which could be a model for protecting and managing tropical forests worldwide.

TYPES OF TROPICAL FORESTS
About half of all the world's forests are in the Tropics, the area between the Tropic of Cancer and the Tropic of Capricorn. This region may be best known for its rain forests - lush, steamy jungles with towering trees, epiphytes, and dense under stories of smaller trees, shrubs, and vines.
Tropical forests are surprisingly diverse. In addition to rain forests, there are mangroves, moist forests, dry forests, and savannas. Such classifications, however, give only a slight indication of the diversity of tropical forests. One study by the Food and Agriculture Organization (FAO) of the United Nations, which considered 23 countries in tropical America, 37 in tropical Africa, and 16 in tropical Asia, identified dozens of types of tropical forests: open and closed canopy forests, broadleaved trees and conifer forests, closed forests and mixed forest grasslands, and forests where agriculture has made inroads.

Rain Forests
The largest remaining areas of tropical rain forests are in Brazil, Congo, Indonesia, and Malaysia. Precipitation generally exceeds 60 inches (150 cm) per year and may be as high as 400 inches (1000 cm). Lowland rain forests are among the world's most productive of plant communities. Giant trees may tower 200 feet (60 m) in height and support thousands of other species of plants and animals. Montane (mountain) rain forests grow at higher elevations where the climate is too windy and wet for optimum tree growth.
Mangrove forests grow in the swampy, intertidal margin between sea and shore and are often considered part of the rain forest complex. The roots of mangrove trees help stabilize the shoreline and trap sediment and decaying vegetation that contribute to ecosystem productivity.

Dry Forests
Large areas of tropical dry forests are found in India, Australia, Central and South America, the Caribbean, Mexico, Africa, and Madagascar. Dry forests receive low rainfall amounts, as little as 20 inches (50 cm) per year, and are characterized by species well adapted to drought. Trees of dry tropical forests are usually smaller than those in rain forests, and many lose their leaves during the dry season. Although they are still amazingly diverse, dry forests often have fewer species than rain forests.
Savanna is a transitional type between forest and grassland. Trees are often very scattered and tend to be well adapted to drought and tolerant of fire and grazing. If fire is excluded, trees eventually begin to grow and the savanna is converted to dry forest. With too much fire or grazing, dry forest becomes savanna. This vegetation type has fewer species of trees and shrubs but more grasses and forbs than other forest types in the Tropics.

VALUE OF TROPICAL FORESTS
All forests have both economic and ecological value, but tropical forests are especially important in global economy. These forests cover less than 6 percent of the Earth's land area, but they contain the vast majority of the world's plant and animal genetic resources. The diversity of life is astonishing. The original forests of Puerto Rico, for example, contain more than 500 species of trees in 70 botanical families. By comparison, temperate forests have relatively few. Such diversity is attributed to variations in elevation, climate, and soil, and to the lack of frost.
There is also diversity in other life forms: shrubs, herbs, epiphytes, mammals, birds, reptiles, amphibians, and insects. One study suggests that tropical rain forests may contain as many as 30 million different kinds of plants and animals, most of which are insects.

Wood and Other Products
Tropical forests provide many valuable products including rubber, fruits and nuts, meat, rattan, medicinal herbs, floral greenery, lumber, firewood, and charcoal. Such forests are used by local people for subsistence hunting and fishing. They provide income and jobs for hundreds of millions of people in small, medium, and large industries.
Tropical forests are noted for their beautiful woods. Four important commercial woods are mahogany, teak, melina, and okoume. Honduras mahogany (Swietenia macrophylla), grows in the Americas from Mexico to Bolivia. A strong wood of medium density, mahogany is easy to work, is long lasting, and has good color and grain. It is commonly used for furniture, molding, paneling, and trim. Because of its resistance to decay, it is a popular wood used in boats. Teak (Tectona grandis) is native to India and Southeast Asia. Its wood has medium density, is strong, polishes well, and has a warm yellow-brown color. Also prized for resistance to insects and rot, teak is commonly used in cabinets, trim, flooring, furniture, and boats. Melina (Gmelina arborea) grows naturally from India through Vietnam. Noted for fast growth, melina has light colored wood that is used mainly for pulp and particleboard, matches and carpentry. Okoume (Aucoumea klaineana) is native to Gabon an the Congo in west Africa. A large fast-growing tree, the wood has mod erately low density, good strength-to density ratio, and low shrinkage during drying. It is commonly use( for plywood, paneling, interior fur niture parts, and light construction.

Other Economic Values
Tropical forests are home for tribal hunter-gatherers whose way of life has been relatively unchanged for centuries. These people depend on the forests for their livelihood. More than 2.5 million people also live in areas adjacent to tropical forests. They rely on the forests for their water, fuelwood, and other resources and on its shrinking land base for their shifting agriculture. For urban dwellers, tropical forests provide water for domestic use and hydroelectric power. Their scenic beauty, educational value, and opportunities for outdoor recreation support tourist industries.
Many medicines and drugs come from plants found only in tropical rain forests. Some of the best known are quinine, an ancient drug used for malaria; curare, an anesthetic and muscle relaxant used in surgery; and rosy periwinkle, a treatment for Hodgkin's disease and leukemia. Research has identified other potential drugs that may have value as contraceptives or in treating a multitude of maladies such as arthritis, hepatitis, insect bites, fever, coughs, and colds. Many more may be found. In all, only a few thousand species have been evaluated for their medicinal value.
In addition, many plants of tropical forests find uses in homes and gardens: ferns and palms, the hardy split-leaf philodendron, marantas, bromeliads, and orchids, to name just a few.

Environmental Benefits
Tropical forests do more than respond to local climatic conditions; they actually influence the climate. Through transpiration, the enormous number of plants found in rain forests return huge amounts of water to the atmosphere, increasing humidity and rainfall, and cooling the air for miles around. In addition, tropical forests replenish the air by utilizing carbon dioxide and giving off oxygen. By fixing carbon they help maintain the atmospheric carbon dioxide levels low and counteract the global "greenhouse" effect.
Forests also moderate stream flow. Trees slow the onslaught of tropical downpours, use and store vast quantities of water, and help hold the soil in place. When trees are cleared, rainfall runs off more quickly, contributing to floods and erosion.

Student Guide