E. Why preserve the tropical rainforests of the world?

Rainforests have a measure of control over many aspects of our environment, and are responsible for much of the terrestrial productivity. These we can call the “essential services” of natural forests.

1) Preservation of biodiversity, which is invaluable to forest productivity (see Part II).

2) Renewable source of forest products, such as timber, medicines, fruits -not to mention chocolate! There is the potential to discover many new foods, domestic animals, industrial products, and medicines in rainforests. Most obviously, rainforests are a source of valuable timber – mahogany, ebony, hard wood dipterocarps from Southeast Asia, and many others less well known. Wood has many properties desirable to humans and animals. It is hard, durable, resistant to many organisms such as fungi, resistant to water, useful as fuel (including charcoal) and as construction material. But in addition, many rainforest plants produce insecticides, herbicides and fungicides which could be useful to humans. For example, leaf-cutter ants will not remove leaves from the tree species Hymenaea courbaril because its leaves produce a fungicide which will kill the fungus the ants cultivate in their gardens (Robinson, 1988) Capuchin monkeys in Venezuela rub themselves with millipedes (Orthotomus dorsovittatus) which secrete benzoquinones, noxious compounds which repel mosquitoes (Angier, 2000). (The massaging may even become a social ritual, with monkeys mutually massaging each other.). A number of plants and trees in the rainforest have proved useful as producers of medicines, and many drugs have been found in the pharmaceuticals of tropical medicine men. Quinine, the first known antimalarial, comes from a neotropical tree, and curare, used as a poison for arrow tips by indigenous peoples in the Neotropics, is also useful for heart conditions. One quarter of our medications come from natural sources; additionally, about 70% of the drugs used today are models of natural chemicals. Most of the medicines from forests have been derived from plants, but many others come from fungi, bacteria and reptiles (snakes). Others remain to be discovered, since less than 0.1% (about 1100) of known plant species has been examined for potential medicinal use. The search for potential medicines and drugs (“chemical prospecting”) is a strong argument for rainforest preservation. It is difficult, however, for a tropical country to receive benefits from the development of pharmaceuticals from their rainforests.

3) Reservoirs for genetic resources and centers for evolution: As we continue to deplete the organisms on earth and homogenize our genetic resources, we increasingly need sources of genetic variability. Since rainforests are so amazingly diverse, they can provide a vast reservoir of genetic potential. Without such genetic resources, we will have no way of improving breeding stocks of plants and animals. All of our domestic plants and animals came from wild antecedents which have been altered by interbreeding and selected for traits which are favorable for human use. As we reduce or eradicate our gene pools, our sources of variability decline dangerously.

4) Regulation of hydrological functions: This is both local and global. Rainforests stabilize water flow, maintain water quality, provide watersheds, and regulate runoff of water from soil. In doing so, they prevent flooding, erosion, landslides, and desertification. Erosion is one hundred times greater on deforested than on forested slopes, for example.

5) Regulation of air quality: Rainforests modify atmospheric chemistry (e.g., they can act as “carbon sinks” and absorb CO2 from the air (see Part I, Section K).

6) Climate stabilization: Rainforests have an influence on rainfall patterns. The humidity and cloud cover over them affect the climate in many other parts of the world. Rainforests create their own moist environment by recycling rainfall. If they are removed, entire regions become drier, and the rainforests remaining may not be able to maintain conditions sufficiently humid for their own survival. Thus, a destructive cycle ensues. Dessication will not simply be local, but regional and global (see Part I, Section K).

7) Soil fertility and retention: Without plant roots, particularly tree roots, to hold them, thin tropical soils are washed away by heavy tropical rains. Soils in deforested areas cannot retain fertility, since most of the organic matter in a forest is in the vegetation, not in the soil, as is the case in temperate forests. Once some of the vegetation is removed, soil humus levels drop precipitously, with a concomitant loss of fertility. And with little vegetation, the complex soil communities of animals, fungi and bacteria are disrupted, severely impeding the possibility of restoring fertility (see Part I, Section L).

8) Control of pests/parasites: Forests are filled with animals (and even plants) which prey upon pests or potential pests (mainly insect) of crops or domestic animals. Complex forest ecosystems are much less subject to outbreaks of infestation or infection than are tree plantations or farms.

9) Pollination services: Many of the animals in forests are the sole pollinators of many forest plants, and they are often highly specific to the plant(s) they pollinate. Loss of forest cover and thus, of animal habitat, has caused and is causing serious problems with the reproduction of forest trees (see Part II, Section F1).

10) Sources of education and knowledge: This includes biological and medical research of all kinds, as well as education for people about natural systems, climate, biodiversity, and soils.

11) Sources of housing for people and animals.

12) Aesthetic factors and sources of recreation

13) A potential source of insight into the relationship between human groups and forests. Not all human societies have had destructive relationships with rainforests, and we need to know about these harmonious relationships as a source of information about agriculture, husbandry, etc.

14) As wilderness, for its own sake.

15) Ethical reasons: Humans, at the moment the dominant species, have a responsibility to protect the earth.

The “services” which forests provide are incomparable; nothing can be substituted for them. Most human efforts to make such substitutions have ultimately been unsatisfactory. These efforts have amounted to serious interventions into natural systems, and add to the human impact on ecosystems and the environment. Among these interventions have been the replacing of natural controls with synthetic pesticides and natural soil maintenance by inorganic fertilizers. Rainforest services are invaluable (although estimates have been made of their monetary worth (see Part II, G8) and it is not an overstatement to say that their economic worth is incalculable or infinite, since we are totally dependent upon other living organisms for our existence.