Habitat destruction and the loss of biodiversity

Of all the issues surrounding environmental change in Amazonia, threats to biodiversity are arguably the most serious in the long run. Species loss as a result of drastic habitat modification, such as logging, is an issue in many parts of the humid tropics, such as in Malaysia (Brookfield, Potter, and Byron 1995). Particularly worrisome is that such biodiversity losses are often not accompanied by any long-term economic benefits to the local people.

The effects of species loss may not be immediately obvious, and are thus not usually considered in economic development plans. Species loss can be hard to quantify in economic terms, and is considered an externality. The impoverishment of habitats is sure to reduce options for future development. Air and water pollution may be more tangible assaults on our living space, but the haemorrhaging of species will drain resources for future generations, quite apart from the ethical and moral questions posed by human-induced extinctions.

Some have argued that we do not really need nature's storehouse of genes because ingenious scientists can concoct novel genes in laboratories at will (Huber 1992). This notion is fallacious. The idea that we can safely dispense with tropical forests or other ecosystems because modern biotechnology has made them redundant is dangerous thinking. Genes need to be synthesized from models. Laboratories and computer memories cannot replicate dynamic evolutionary processes under way around the world.

Impressive advances in biotechnology only underscore the importance of conserving biodiversity since desirable genes can increasingly be switched from one organism to another. The glamour of genetic engineering should not blind the public and policy makers to the need to safeguard the integrity of natural ecosystems.

Loss of biodiversity as a result of development and environmental degradation has emerged as a global concern (Raven 1990; Wilson and Peter 1988). Concern over erosion of biodiversity was initially confined mostly to the scientific community, but is now spreading to the general public and politicians. Tropical deforestation is often at the forefront in debates on biodiversity loss; at least 27,000 species are thought to be lost from such widespread destruction every year (Myers 1993). Actual species loss may be much higher considering that many plant and animal groups are still imperfectly known (Wilson 1992). Amazonia has attracted particular attention in this regard because of its high degree of endemism and vast numbers of animal and plant species, many of them undocumented or poorly studied (Adds 1990). The region's diverse array of plant and animal communities contains many unique species and genes.

Amazonia contains the largest stretch of tropical forest, spanning 5,000 km from the Andes to the Atlantic, and some 4,000 km from the Guianas and the Upper Orinoco to the scrub cerrado of the Brazilian shield and the seasonally flooded grasslands of the Pantanal. This vast mosaic of forest communities, second growth, natural and man-induced grasslands and swamps contains the richest assortment of plant and animal species in the world, as well as a rich storehouse of genes for crop improvement.

Deforestation can adversely affect biodiversity on two accounts: outright habitat destruction, and ecological changes along the contact zone of remaining forest stands. Whereas deforestation rates in Amazonia appear to have been less dramatic over the past decade than has previously been thought, perhaps in the order of 15,000 km per year during the 1978-1988 period, some 38,000 km of forest may have been degraded (Skole and Tucker 1993). The edge effect of disturbance, ranging from microclimatic changes to the encroachment of swidden and pasture fires, can allegedly alter plant and animal communities as much as 1 km into the forest. Although some may dispute how deeply human influences penetrate the forest in terms of significant ecological disturbance, it is clear that outright deforestation alone is an insufficient measure of biodiversity change. In drier areas of the Amazon, such as around Maraba in southern Pará and in southern fringes of the rain forest in Mato Grosso, the border of isolated patches of forest can easily catch fire when fields or grazing areas are torched in preparation for planting or to destroy weeds and promote new growth of pasture grasses.

Endangered gene pools

Rampant deforestation fuelled by development schemes and pioneer farmers now threatens to destroy the genetic resources of many economic plants and potential crops before they can be tapped for the benefit of people throughout the world (NRC 1991; Smith et al. 1991b, 1992). Also, loss of tribal cultures is resulting in the disappearance of unique varieties of many annual and perennial crops.

Wild populations of crops, and in some cases their near relatives, are increasingly sought by plant breeders for desirable traits, such as pest and disease resistance and tolerance to problem soils. To help make farming more sustainable, researchers, development organizations, and farmers are increasingly seeking genetic solutions to agricultural constraints rather than costly, and sometimes environmentally damaging, chemical applications.

Ironically, forest-clearing to establish farms and plantations can eliminate the very genes that could be used to improve the crops being planted. The shrinking of wild populations of over 47 perennial crop species is currently under way in Amazonia (Smith and Schultes 1990). Perennial crops are important to the livelihoods of most small farmers in the tropics as well as operators of large plantations. Perennial crops that originated in Amazonia provide food, beverages, shelter, medicines, oils, resins, cosmetics, food colourants, and latex for citizens on every continent.

The Amazon contains wild gene pools of such commercially important crops as rubber (Hevea brasiliensis) and cacao (Theobroma cacao), as well as regionally important food and beverage crops such as peach palm (Bactris gasipaes) and guarana (Paullinia cupana), a popular soda in Brazil and now exported to developed countries such as Canada. As the heart-of-palm trade destroys many wild stands, particularly species of Euterpe, entrepreneurs in several Latin American countries are planting peach palm for palmito. Plantations of peach palm for the heart-of-palm trade are especially well developed in Costa Rica and Mexico. The ability of developing countries in the Amazon region as well as in other parts of Latin America, Africa, and South-East Asia to raise and sustain yields of several important cash and food crops will hinge to a large extent on their ability to marshal genetic resources to overcome constraints to production.

The Amazon forest also contains wild populations of hitherto minor crops such as annatto (Bixaorellana) and cupuaçu (Theabroma grandiflorum). Annatto is used by some Indians for body paint and is commonly used as a food colourant in Latin America. Known as achiote in Spanish and urucú in Brazil, annatto occurs spontaneously in various parts of Amazonia and probably originated in Acre. Traditionally, annatto has been grown as a backyard plant but it is now being cultivated on a commercial scale in several Latin American countries, particularly Brazil. After artificial Red Dye No. 3 was banned in the United States because it is a carcinogen, interest in annatto rebounded. Natural red bixin from annatto is increasingly used to colour foodstuffs and cosmetics in both industrial nations and developing countries. Annatto is used to enhance the colour of some peach-flavoured yogurts in the eastern United States, although few consumers probably make any connection with Amazonia when they relish that healthy treat.

Football-sized cupuaçu, a relative of cacao, grows in the forests of eastern Amazonia and is cultivated in backyards and fields for its refreshing pulp, which is used to make drinks, ice-cream, cakes, and puddings . Cupuaçu sells briskly in Amazonia and is penetrating markets in southern Brazil, and more recently in the United States and Japan. Cupuaçu has made the transition from an extractive product, to an occasional plant in home gardens, to a full-fledged crop, often grown in agro-forestry systems. How many other "cupuaçus" linger in the forest that could one day delight the palate of people in the region and abroad?

Amazonia's lush and diverse forests also contain many plants that could be incorporated into our menu of cultivated species, or are currently on the threshold of domestication. The nuts of patauá (Jessenia bataua) palm, for example, contain an oil similar to the quality of olive oil. The fruits are collected in the wild to make refreshing drinks. Brazil nut is now being grown on a small scale on several private landholdings in the Brazilian Amazon as well as in Malaysia. Domestication of Brazil nut is an important step considering that wild stands of the giant forest tree are falling for ranches, farms, and reservoirs.

Forests also contain pollinators and dispersal agents of wild populations of many crop plants as well as their near relatives . Intricate and often fine-tuned relationships between plants and animals need to be maintained if the integrity of many wild populations of our crop plants is to be ensured. For example, Brazil nut is dispersed by agoutis (Dasyprocta spp.), which bury many of the nuts after gnawing open the hard capsules that encase the protein- and oil-rich nuts (Huber 1910). Some bats pollinate forest trees while others disperse their seeds, and many birds, such as toucans, guans, and curassows (Cracidae), also disseminate many forest fruits. Conservation of forest environments, as well as field gene banks, is thus essential for the long-term viability of many crops important for subsistence and commerce.

Conservation of genetic resources and regional development in Amazonia are intertwined. More studies are needed, however, to document genetic variation in wild populations and domesticated gene pools of Amazonian crops. Also, hard economic data are needed to convince policy makers of the value of preserving forest habitats as resources for development.

Another dimension to the loss of botanical resources in Amazonia is that an invaluable medicine chest is literally being depleted before we can assess even a fraction of the potentially useful drugs. The rapid decline of many indigenous societies represents a loss not only of crop plants and unique varieties, but of ethno-botanical knowledge about which trees, shrubs, and herbs in the forest might offer cures for a wide variety of health complaints (Plotkin 1993). Many drugs are eventually synthesized in laboratories but, as in the case of genes for crop improvement, they have to be discovered first.

The indigenous knowledge base

A salient lesson from global efforts to conserve crop genetic resources is the need to maintain the cultural integrity of indigenous groups. People with a long history of interaction with the forest have much to teach us about sustainable agricultural practices and plant resources. Rural folk are particularly knowledgeable about the location and natural history of wild populations of crops and their near relatives. Tribal peoples are also knowledgeable about the medicinal value of plants in the forest and in their home gardens, a priceless heritage that is increasingly threatened by encroaching civilization (Schultes 1988; Schultes and Raffauf 1990, 1992). Biodiversity and cultural heterogeneity are vital to sustainable development.

Although rural peoples often have affinity with the surrounding plant and animal world, their practices do not always result in conservation of resources. Peasants and ranchers alike frequently clear fields and home gardens up to the margins of streams or rivers. If water courses were left in forest, natural corridors would remain for animal and plant dispersal in cleared areas.

Farmers in the Brazilian Amazon report three main reasons why they fell riparian forests, even if they contain economically important species such as açai palm (Euterpe oleracea). First, several crops important for domestic consumption and commerce grow well in the moist, organic-rich soils flanking streams and small rivers in contrast to the generally highly acidic, nutrient-poor upland soils. The common bean (Phaseolus vulgaris), maize (Zea mays), and vegetables reportedly yield better when grown in humid, valley bottoms. It is also easier to irrigate vegetables when they are close to a perennial water source. Second, farmers want to eliminate habitat for predators on their small livestock, particularly ocelot (Felis pardalis), margay (Felis wiedii), and various hawks. Third, newcomers to the region do not yet appreciate the value of some riparian trees and wish to create open, more "productive" landscapes.

Faunal resources

The forests and rivers of Amazonia also contain an abundant array of wildlife important for hunting (Ayres and Ayres 1979; Ayres et al. 1991; Bodmer, Fang, and Ibanez 1988, 1991; Dourojeanni 1974; Rios, Dourojeanni, and Trovar 1973; Smith 1976). Some game animals, such as various species of turtle (Podocnemis spp.), could be domesticated or reared in captivity and the young released to the wild. Of the many species of mammals, birds, and reptiles of lowland South America, only one species has been domesticated, the muscovy duck (Cairina moschata). Muscovy ducks still grace the extensive lakes and lagoons of the Amazon flood plain, and some of these wild populations could be helpful to further breeding efforts.

Several wild animals are kept around homes for eventual consumption and some of them are in the process of being domesticated. Most are captured while still young, particularly when their mothers are killed during hunts. Capybara (Hydrochaeris hydrochaeris) and black-bellied tree ducks (Dendrocygna autumnalis) are kept around homes by some farmers along the Amazon flood plain, and they sometimes breed in captivity. Options for animal domestication will be foreclosed if wild populations of such species are drastically reduced.

Habitat destruction is the principal threat to wildlife in the region. The issue of dams and fisheries has already been highlighted, but the clearing of floodplain forests by farmers and ranchers also eliminates breeding and feeding grounds for fish. At least three-quarters of the fish species important in commerce and subsistence derive their nutrition directly or indirectly from flooded forests (Goulding 1980, 1993). A better understanding of land-use systems is thus essential for improved development and conservation efforts.

Policy implications

Although Amazonia is rich in plant and animal species, particularly in forests cloaking the eastern slopes of the Andes, policies that might deflect settlement and development to relatively empty areas, such as cerrados and thorn scrub, need to be considered carefully. Some of the drier areas of South America have higher levels of mammal endemism than the rain forests (Mares 1992). The campos, cerrados, and thorn scrub woodlands (caatinga, Chaco) of South America are much richer in animal and plant species than is generally appreciated (Pimm and Gittleman 1992). Wholesale destruction of low rainfall environments would also greatly reduce biodiversity - and future options for sustainable development in those areas.

The expansive flood plain of the sinuous Amazon River is another perceived venue for increased development efforts. The Amazon flood plain has always been regarded as an underutilized environment in Amazonia with enormous potential for raising food crops, livestock, and fish. Yet the idea that the flood plains can help absorb development pressures from the "fragile" upland forests warrants careful scrutiny. Flood-plain forests along the Amazon have already been largely logged out and extensively cleared. Endemism is especially high in the seasonally flooded forests of the Amazon River. Efforts to boost the productivity of flood-plain areas should focus on already cleared areas, rather than promote the wholesale destruction of the remaining forest and aquatic habitats with the* rich assortment of wildlife.

To help preserve the remaining biodiversity in Amazonia and to reduce pressures to develop contiguous regions, the productivity of agriculture, managed forests, plantations, and ranches must be raised within the well-watered basin. Whenever feasible, such land-use systems should be ecologically diverse. Agro-forestry systems, highlighted later as one of the more viable options for agricultural development in the region, could help maintain some level of biodiversity. Compared with simple monocultures, agro-forestry permits the survival of more animals and plants (Holloway 1991). Also, monocultures of perennial crops, such as oil-palm, create microenvironments for such plants as lichens and mosses that cannot survive in fields of rice or maize.