About one third of the world’s forests are tropical rain forests. They are the most ancient, diverse, complex, and productive ecosystems on the terrestrial surface of the Earth. Although they cover only about 6-8% of the land surface, they contain about half of all life, whether this is measured by the number of species (biological diversity) or organic weight (biomass). These forests form a discontinuous green belt around the equatorial regions of the planet, concentrated within ten degrees latitude north and south of the equator but extending in many areas to 23.5 degrees north and south within the tropical zone. About half of the world’s tropical rain forest is in the Amazon region, and about 80% of that is in Brazil.
In tropical rain forests the average yearly temperature is 20-28°C or more, while the average yearly rainfall is above 2,000 mm. The climate is the closest to the optimal conditions for plant growth anywhere on Earth with its combination of high temperature, rainfall, and humidity. Consequently, this type of forest is the norm for plant growth on this planet, while every other kind of plant community is some deviation in response to one or more kinds of stress such as lower rainfall or lower temperatures.
Water plays an extremely important role in the variation and dynamics of ecosystems in the tropical rain forest, as is implied by the designation rain forest. Rivers, streams, lakes, and swamps are found in many areas, and they are important to local people for water consumption, transportation, and trade, as well as for fish, birds, and other game for food.
The plant community of the tropical rain forest is characterized by its stature, luxuriance, and diversity. In mature forests there are giant trees, with few if any branches in their lower levels, standing like columns in a grand cathedral. Such forest is more or less stratified, with several layers that reflect vertical zonation in the microclimate and associated biota.
Animals are an important component of the structure, function, composition, and dynamics of these ecosystems. However, animals are relatively scarce. While their species diversity is high, their population density is low and individuals within a population are patchy in distribution. Furthermore, most animal species are arboreal, small in body size, solitary, camouflaged, and nocturnal. In addition, invertebrates such as ants and termites comprise most of the faunal biomass of the forest. The major exception to these generalizations about animals is the wild pig, which is terrestrial, large in body size and group size, diurnal, and noisy, and leaves obvious trails. Accordingly, in most tropical rain forests, wild pigs are usually the most important item by weight in the annual predation record for many indigenous hunters.
Since Europeans first started exploring tropical forests in the 15th century, this biome has probably attracted more attention than any other type of environment. It stimulates different reactions, depending on whether the observer’s agenda is economic, political, religious, artistic, or scientific. Furthermore, the ambivalence of Western civilization toward the “jungle” is reflected in numerous binary oppositions like paradise/hell, rich/poor, harmony/chaos, peace/war, good/evil, and so on. That is, some people consider the forest to be a type of Eden, while for others it is Hades. This ambivalence is reflected in some local cultures as well. For example, as described by Colin Turnbull, in the Congo region of Africa, the Mbuti people who live inside the forest view it as affectionate and protective like parents, while Bantu neighbors dwelling on its margins consider it to be a dangerous place filled with evil spirits.
Such contradictory and contested images are also reflected in the scientific literature, although usually more subtly. The native or indigenous peoples of the forest have been viewed ambivalently by Western civilization as either “noble savages” (via Jean-Jacques Rousseau) or “bestial savages” (via Thomas Hobbes). In the ethnographic record of the Amazon, these positive and negative representations are exemplified respectively by Gerardo Reichel-Dolmatoff’s publications on the Desana and Napoleon Chagnon’s on the Yanomami. Usually more recent ethnographies are better balanced.
A rich source of reliable and detailed information about the natural history of the animals, plants, and ecosystems of the tropical rain forest is the local human community, especially indigenes. People who regularly engage in subsistence hunting, fishing, gathering, or farming in this ecosystem usually accumulate reliable and detailed knowledge of the species they seek for food in order to survive. What has been termed traditional environmental knowledge (TEK) can be critical in any attempts by outside agents to promote environmental conservation or economic development in tropical rain forests and other environments. Indeed, many such interventions have failed with dire social and environmental consequences because they ignored local cultures, TEK, and the like. Most, although not all, traditional indigenous societies have more often than not been sustainable, a fact proven by their continued existence as the descendants of the original inhabitants of an area over centuries or even millennia.
Forests survived in much of the tropics while humans inhabited them for centuries or even millennia, although in certain areas, such as those of some of the Maya in Central America and various islands in Polynesia, deforestation occurred already in prehistory. For the most part, however, deforestation in places like the Amazon is a recent phenomenon of the last few decades and is related to the introduction of alien technologies and economies as well as regional, national, and international politics.
Only since the 1960s has the rate of deforestation in the tropics become alarming. Through space and over time, different combinations of factors contribute to deforestation. These include cattle ranching in tropical America, government colonization schemes in the Brazilian Amazon and the Indonesian outer islands, gold mining in Brazil, oil extraction in Ecuador and Peru, plantation monocrops like rubber trees in South and Southeast Asia, and hydroelectric dams in various areas.
Cultural diversity and biological diversity are both extraordinarily high in tropical rain forests, a coincidence that is called the diversity principle. (Both types of diversity decrease progressively from the equator toward the poles.) Conservationists identify Brazil, Congo, and Indonesia as among the megadiversity countries because of their high biodiversity. Such countries contain high cultural and linguistic diversity as well. They are also the hot spots (endangered areas) for both tropical rain forests and indigenous cultures. These two endangered phenomena are interrelated and cannot be considered in isolation from each other. Moreover, traditional environmental knowledge as well as land and resource use, management, and conservation practices are indispensable to consider in countering the threats to these cultures and to their forest habitats from both the human rights and environmentalist perspectives.
The awesome cultures and environments of the tropical rain forests have far too much intrinsic value to sacrifice merely for the material “progress” of the contemporary consumer society. The latter is predicated on infinite growth on a finite base, which is an impossibility. Such ecocidal societies are destined to self-destruct sooner rather than later. The tropical rain forest, the people who consider it their homeland, and their cultures and religions deserve to be appreciated and respected on their own terms. Tropical rain forests are the last refuges for biological and cultural diversity on Earth, and diversity is indispensable for continued adaptation and future adaptability.
- Lye, T., de Jong, W., & Ken-ichi, A. (Eds.). (2003). The political ecology of tropical forests in Southeast Asia: Historical perspectives. Kyoto, Japan: Kyoto University Press.
- Maffi, L. (Ed.). (2001). On biocultural diversity: Linking language, knowledge, and the environment. Washington, DC: Smithsonian Institution Press.
- Slater, C. (Ed.). (2003). In search of the rain forest. Durham, NC: Duke University Press.
- Whitmore, T. C. (1998). An introduction to tropical rain forests (2nd ed.). New York: Oxford University Press.
- Williams, M. (2003). Deforesting the Earth: From prehistory to global crisis. Chicago: University of Chicago Press.