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A major preoccupation with environmental change in Amazonia hinges on deforestation and the loss of plant and animal resources, including fisheries. Much attention currently focuses on how to arrest this destruction. A confluence of forces is implicated in the destruction of habitat in the region, and the preponderance of forces responsible for the retreat of forest and disruption of other environments varies widely according to such factors as access to markets, road infrastructure, and fiscal incentives. Loggers, cattle ranchers, dam builders, smallholder farmers, and plantation operators are all involved in deforestation. Throughout the tropics, it is argued by some, smallholder farmers account for more deforestation (some 60 per cent) than the next two agents of destruction, commercial loggers and ranches, combined (Myers 1991). Even in the Amazon, where ranching is a widespread occupation, smallholder farmers probably account for more than one-half of the forest cleared each year.
Fig. 2.2 Trends on land-use systems in response to increasing population density in Amazonia (Source: adapted from Serrão and Homma, 1993)
A variety of driving forces propels these "actors" in the drama of regional transformation in Amazonia. Proximate agents of environmental change (e.g. smallholder farmers) are not necessarily to blame for adverse ecological impacts in Amazonia. An analysis of the driving forces behind these agents of forest removal will help clarify policy issues for future development.
Although many forces propel environmental change in Amazonia and other regions, they fall conveniently into five main categories that generate demand for or facilitate the removal of the resources in the area. These are: changes in population, new technologies, socioeconomic and institutional conditions, the influence of beliefs and attitudes, and income and wealth. The interplay of these factors varies considerably from one part of Amazonia to another, but they are all involved in altering the landscapes and cultures of Amazonia.
Population change
Population pressure is often portrayed as a root cause of environmental degradation in many third world countries, particularly with regard to deforestation (Westoby 1989, 45). Although rapid population growth undercuts the natural resource base in some developing regions, it is hard to conceive of Amazonia having a population problem per se. The pre-contact population of Amazonia was denser in many rural parts of the basin than it is today (Smith 1980; Smith 1995), but the environmental impacts of the prehistoric population are poorly understood. Forests recovered, albeit in altered form. Even in regions perceived as suffering from overpopulation, though, overtaxing of the land may occur owing to inappropriate technologies or highly skewed patterns of land ownership, among other socioeconomic factors.
Except in a few restricted areas, such as south-western and southeastern Amazonia, population growth is a relatively minor force behind environmental change in the region. This growth is not internal to Amazonia, but exogenous, in so far as farmers, itinerant miners, and ranchers migrate to the region (Schmink 1988). There, new waves of settlers and speculators are mainly responsible for the retreat of forest and other ecological changes in Amazonia. Population growth in Amazonia is concentrated in Rondônia and southern Pará as incoming settlers from Paraná, Rio Grande do Sul, São Paulo, and Minas Gerais flood these areas.
When coupled with environmental hazards or overcrowding in environmentally sensitive areas, such as the Andean altiplano, migrants pour out from their hard-pressed source areas. Periodic droughts in the north-east of Brazil, for example, have pushed victims into Amazonia for over a century. Substantial proportions of the inhabitants of the Brazilian Amazon trace their roots to the arid backlands of the north-east. The impact of droughts in the north-east is exacerbated by the skewed land distribution pattern; the poor majority suffer most when the rains fail because they generally till marginal lands.
Two main migration currents are discernible in countries embracing Amazonia: a substantial rural exodus to towns and cities, and settlers penetrating the Amazon Basin along pioneer roads. For every migrant heading for Amazonia, though, many more have opted to settle in towns and cities. During the 1970s, some 766,000 people migrated to the Brazilian Amazon, accounting for only 5 per cent of the flow of people moving from the countryside to urban areas (Wood and Carvalho 1988, 234). Amazonia, therefore, is clearly not serving as a convenient safety-valve for population growth and socioeconomic problems in other regions.
In Latin America, urban population growth is generally much higher than growth in rural areas, and this holds for countries with territories in Amazonia. Throngs of sharecroppers, unsuccessful or dispossessed farmers, and grown children of rural families have caught buses or trucks in search of new livelihoods in Latin America's swelling cities. Rural-urban migration has severely stretched the ability of rapidly growing cities to provide services for newcomers, and many settle in slums. Some shanty settlements around cities eventually improve, or people move out into better neighbourhoods after a few years if they have acquired some savings, but urban migrants rarely return to live or even work in their source areas.
Cities are a magnet to prospective migrants. Urban areas, in spite of their higher living costs, crime, and pollution, offer better opportunities for jobs, schooling, and health care. In contrast, pioneer areas of Amazonia have fewer health and educational facilities, and roads that become impassable in the rainy season can isolate farmers from markets, hospitals and clinics, schools, and needed supplies. This impressive sponge effect of cities has undoubtedly saved the Amazon from even more extensive deforestation.
The Andes and southern Brazil are currently the main source regions for Amazonian migrants. The crowded Andean valleys of Peru, Bolivia, Ecuador, and Colombia have sent aspiring landowners down into western and southwestern Amazonia for several decades (Crist 1967; Eidt 1962; Hicks et al. 1990, 2; Hiraoka 1980; Rudel 1983; Stearman 1978). In the Brazilian Amazon, the north-east has long served as an important source of migrants for much of the basin, but the growing throng of settlers from southern Brazil has eclipsed their numbers.
The greatest influx of settlers into the Brazilian Amazon since the 1970s has come from such states as Paraná, Rio Grande do Sul, São Paulo, Minas Gerais, and Espírito Santo. Population growth is partly responsible for the flow of migrants to Amazonia, particularly in Paraná, and Rio Grande do Sul, where small farms are divided up among sons and have, in some cases, become too small to be economically viable. Minifundia, rather than latifundia, are thus more of a problem in some parts of southern Brazil. In north-western Rio Grande do Sul, for example, areas pioneered in the 1940s had already become full by the early 1970s.
Other factors also account for out-migration from rural parts of southern Brazil to Amazonia and cities. Unequal distribution of land in some areas presses the landless in search of new lives and homesteads. Moreover, changes in farming methods (see below) can lead to redundancy for some farm labour.
In spite of more than two decades of intensive efforts to accelerate settlement and development and the influx of migrants, Amazonia remains relatively sparsely settled. The 3.8 million km² Brazilian Amazon contains only 10 million inhabitants, fewer than the megalopolis of São Paulo, and a density of population of less than 3 people/ km². The Brazilian Amazon accounts for 45 per cent of Brazilian territory but less than 7 per cent of its population.
Overall, population pressure has clearly not reached any serious proportions in Amazonia, at least by comparison with the density of populations found elsewhere in tropical forest zones. Some rural areas of Amazonia have actually lost people to cities in the last two decades. A little over half of the population in Amazonia resides in urban areas, and Belém alone has over 1 million inhabitants. Population growth rates in Amazonian towns and cities far exceed those in rural areas (Godfrey 1990).
Growth in population has triggered environmental change, but the numbers are simply not sufficiently high to create large-scale environmental degradation in the region. Given that the rural poor and other land users in Amazonia tend to use "effective" technologies (i.e. practices that often require frequent and large-scale clearing of forest), any future population increases are likely to result in further clearing of forests.
Technological change
Changes in technology for agriculture, forestry, and mining, among other activities, can have adverse impacts on the environment. Few would deny that humankind's ability to alter the face of the earth and the atmosphere has increased dramatically with ever more potent technologies. The literature is replete with examples of technological changes that have wrought ecological destruction and social disruption (Bennett et al. 1974; Nelson 1973; Norman 1981; Turner et al. 1990), and this is so for Amazonia as well. But technologies can also be used to help manage resources more wisely, as is occurring in various parts of Amazonia.
Technological changes in agricultural areas elsewhere in Brazil may indirectly affect the environment of Amazonia. Such changes in southern Brazil have been cited as forcing people off the land, and some of them have moved to Amazonia. A switch to machine-intensive soybean production from more labour-intensive coffee production in parts of Paraná, for example, has allegedly contributed to the rural exodus (Wood and Carvalho 1988, 207). The widespread use of tractors on soybean farms has allegedly displaced labour, thereby contributing to migrants streaming into Amazonia (Muller 1988a).
Mechanization may have reduced on-farm labour needs, but it is not clear whether the increased use of tractors in southern Brazil has spurred migration to Amazonia or other parts of the country. The manufacture and servicing of agricultural machinery, combined with the impressive volume of soybean transportation and processing in Brazil, have undoubtedly created many new jobs. Some farm labourers are likely to have moved to the service sector in urban areas, rather than try their hand at farming in Amazonia.
Mechanization does not necessarily push small farmers off the land. In areas of Paraná, settled by private land companies, or where farmers are members of efficient cooperatives, small landholdings remain viable in the face of mechanization and soybean cultivation (Muller 1988b). Rapid soil erosion and consolidation of landholdings by ranchers in Paraná, rather than technological change, have been mainly responsible for the demise of some small farms and an exodus of people from rural areas (Muller 1988b).
Sophisticated technologies are also not necessarily the major proximate sources of change in Amazonia. Small-scale farmers employing axes, machetes, and (in some cases) power saws are probably clearing more forest in Amazonia than any other agents. Even large landholders generally employ work gangs armed with power saws or axes to clear land. Indians formerly used stone axes to fell forest and, as has been argued previously, were quite capable of radically altering the plant geography of Amazonia.
Dam-building is radically altering the regimes of certain rivers (especially the Tocantins) and has flooded extensive areas of both upland and flood-plain forest. Thus far, the impact on fisheries appears to be minimal, but long-term loss of genetic resources of plants caused by the ensuing reservoirs could be appreciable. Along the Tocantins, for example, the Tucurui dam has inundated extensive populations of Brazil nut trees. A global recession and concern about environmental impacts on peasant and indigenous groups have slowed hydroelectric dam construction in Amazonia. As the world economy improves and fossil fuel prices climb, more dams are likely to be built in the region. An increased reliance on solar-based technologies and improved conservation measures could alleviate the demand for electricity. Some farmers on the Amazon flood-plain near Santarém, for example, have ordered water-pumps powered by photovoltaic cells from southern Brazil to irrigate their vegetable crops.
Introduced technologies can be a double-edged sword for the environment and society with respect to cattle-raising as well. African pasture grasses, particularly guinea grass (Panicum maximum) and jaraguá (Hyparrhenia rufa), helped make cattle-raising an attractive undertaking in Amazonia in the 1970s. The carpeting of substantial tracts of Amazonia with pasture grass stirred heated debate about appropriate land uses in the region. Now, both small and large ranchers are experimenting with "later generation" African pasture grasses, such as briachiarão (Brachiaria brizantha), in an effort to upgrade pastures and improve productivity. In this manner, pressure on the remaining forest is likely to be reduced, as will be explored in more detail later.
Socio-economic and institutional change
The fiscal and agrarian policies of the Brazilian government have significantly shaped land use in Amazonia since the late 1960s. Beginning in 1967, companies could invest up to one-half of their taxes in approved development projects in Amazonia. Administered by the Superintendency for Amazonian Development (Superintendência de Desenvolvimento da Amazonia, or SUDAM), projects supported by tax incentives were responsible for clearing over 10 million ha of forest, mostly for cattle pasture (Hecht and Cockburn 1989).
The large-scale conversion of forest to cattle pasture has proved to be the single most controversial aspect of fiscal policies in Amazonia during the 1960s and 1970s. As concern mounted about the ecological implications of such a rapid land transformation, and as the often disappointing productivity of many new ranches became apparent, the government suspended fiscal incentives for the development of cattle pasture in dense tropical forest in 1979. Nevertheless, many projects approved before 1979 were still being implemented in the 1980s. Furthermore, transitional forest skirting the basin was eligible for fiscal incentives to create pasture. SUDAM incentives accelerated pasture development in Amazonia, particularly in southern Pará and northern Mato Grosso, but overall they have accounted for less than 10 per cent of deforestation in the region (Mahar 1989, 15). On 25 June 1991, President Collor signed a decree removing fiscal incentives for cattle-ranching in any forested portion of the Amazon, including transitional forest.
Cattle-ranching remains one of the most common land uses in recently cleared areas of Amazonia, even without fiscal incentives. Cattle-ranching is a favoured occupation of large and small to medium-size holdings in the region because labour is scarce and a ready market exists for beef, particularly in the rapidly growing urban centres (Hicks et al. 1990, 14). If roads are impassable, cattle can still reach market. Cultural factors stemming from the tradition of cattle-raising in Iberia have sustained the conversion of formerly forested land to pasture in many parts of the region, including eastern Ecuador (Hiraoka and Yamamoto 1980).
Government-directed colonization schemes have opened up vast stretches of hinterland to settlers. In 1970, the Brazilian government announced the national integration plan, Programa de Integração Nacional (PIN), which called for a system of pioneer highways to criss-cross Amazonia, with the 3,000 km Transamazon Highway serving as the main east-west axis for the new highway system. PIN highways were initially designed to serve homesteads for drought victims in the north-east and the numerous large families of landless and small farmers from other parts of Brazil. The highways were further designed to create access to resources, such as minerals.
The road network in the Brazilian Amazon has grown spectacularly, from a total of 6,350 km in 1960 to 43,672 km by 1985 (Homma, Texeira Filho, and Magalhaès 1991). Tens of thousands of settlers have followed the bulldozers to take up lots in government-sponsored settlement schemes, to squat on unoccupied land, or to invade reserves and private holdings. By the mid to late 1970s, several private land companies were opening up substantial tracts of land in southern Pará and northern Mato Grosso to medium- and smallholder farmers.
Occupation of Amazonia would occur even without government incentives. A case can be made that certain government policies have accelerated rates of settlement and forest conversion, but they can hardly be blamed for widespread ecological change in Amazonia. Government policies have influenced the locations of such change, but many land-hungry settlers and investors are already motivated to try their luck in Amazonia. A desire to tap natural resources and seek new fortunes is a powerful enough incentive, and, as frontiers close in other parts of Brazil, eyes naturally turn to Amazonia, one of Brazil's last remaining frontiers.
Migration to and within Amazonia is sometimes attributed to a skewed distribution of land. Unequal access to land both within Amazonia and in other parts of Brazil, it is argued, uproots people and obliges them to seek a new life in frontier zones. Debate on whether drought, population growth, or latifundia are responsible for the long history of out-migration from north-eastern Brazil has continued for a long time (Hall 1978). All three factors are responsible in varying degrees, depending on the area in question. Without stepping too far into this complex question, it suffices to say that land ownership patterns have undoubtedly caused social conflicts in some parts of Brazil, particularly southern Pará and are partly responsible for migration to and within Amazonia.
The need for some degree of land reform and the expediting of secure land titles has been recognized for a long time in parts of Brazil and other areas of Latin America. Confusion over land titling has fuelled deforestation, since one of the most visible ways to place a stamp of ownership on the land is to clear it, even if the opened space is not used productively (Schmink and Wood 1987). Historically, the politically more expedient solution to the greatly skewed land ownership pattern in Latin America has been to open up "unoccupied" land for the needy, rather than tackle powerful landowning interests or invest in technologies to boost productivity (Wood and Schmink 1978). But even if significant land reform were carried out in Brazil, it is debatable whether breaking up large estates would greatly alleviate the flow of people to Amazonia. Land reform can exacerbate social problems by reducing agricultural production and dismantling managerial expertise for certain agricultural enterprises.
Subdividing land is thus not necessarily a cure-all for sustainable development and for saving vast tracts of Amazonia. In southern Brazil, minifundia rather than large landholdings are a significant cause of out-migration to Amazonia. In western Paraná, and Rio Grande do Sul, for example, areas opened up for settlement in the 1940s and 1950s are already crowded. Further subdivision of lots for future generations is not feasible in many areas, such as around Tenente Portela in Rio Grande do Sul. In Peru, land reform has been carried out for several decades, but thousands of migrants still pour out of the packed altiplano in search of jobs in cities, such as Lima, or to eke out a living in the forests carpeting the eastern flanks of the Andes.
National beliefs and manifest destiny
Amazonia has long been considered a cultural and economic backwater. Although still considered exotic and steeped in mystery, at least in public perception, Amazonia is rapidly being incorporated into the heartlands of countries with a stake in the sprawling region. Brazil has been the pace-setter in implementing projects to integrate the region better into national society. In the 1960s and 1970s, the Amazon was seen as a region of great potential that warranted massive investments, from both national governments and international agencies. Enormous investments were made to upgrade transportation, communications, and electric-power networks. New roads would carve avenues to El Dorados, long entombed under the mantle of forest.
Although heavy government investment in Amazonia continued in the 1980s, the prevailing attitude of national governments shifted to the idea that the region should start "paying for itself." The downturn in the global economy during the 1980s and mounting budget deficits prompted governments to perceive the region more as a fountain of revenue, rather than as a sinkhole for public investments. Attempts were also made to shift more of the burden for development to the private sector, in part because some of the public sector investments, such as in planned settlements, were expensive and often produced disappointing results.
The authoritarian governments that ruled Brazil from 1964 to 1985 laid down bold development strategies for the Brazilian Amazon. Several military strategists associated with the military academy (Escola Superior da Guerra) erected the intellectual girders of these development plans. Civilian scholars and scientists, such as the economists Delfim Neto and Mario Henrique Simonsen, were also involved in rationalizing development plans. Gifted civilian technocrats were thus a critical part of the "revolutionary" governments and often occupied key administrative posts.
The revolutionary military governments that steered Brazil for 21 years have been blamed for much of the rampant destruction in Amazonia (Bunker 1985; Hecht and Cockburn 1989). The World Bank has also been criticized for funding portions of the Polonoroeste project, which included asphalting the Cuiabá-Porto Velho Highway through Rondônia. The World Bank has since withdrawn support for development projects in Amazonia.
The process of incorporating Amazonia into the respective national orbits would have occurred without SUDAM-approved projects, government settlement schemes, or World Bank loans. The building of roads into Amazonia was inevitable. Before the road to Brasilia was completed in 1964, Belém could be reached only by air or sea. Even asphalting highways does not necessarily speed up settlement; rather, all-weather roads increase land values and farmers may be more inclined to invest in more intensive farming methods.
No single ideology or belief system can be "blamed" for the environmental changes under way in Amazonia. Several governments with different organizational structures and ideologies have been involved over the last few decades, and all have sponsored development and settlement schemes in the region. Only Venezuela, and to a certain degree Colombia, have been relatively cautious with regard to opening up their Amazonian territories, but then those countries occupy comparatively small segments of the region. Trends towards cattle-ranching, increased gold-mining, petroleum exploration, and deforestation are common to all countries with stakes in Amazonia (Barbira-Scazzocchio 1980; Hemming 1985a,b; Hiraoka and Yamamoto 1980; Moran 1981; Schmink and Wood 1984).
The notion that authoritarian governments are more damaging to Amazonia than democratic regimes does not hold water. In Peru, the democratically elected government under Alan García (who held office until 1990) did not stem widespread deforestation in western Amazonia. Brazil now has a democratic government and development pressures on Amazonia are increasing.
A development ethic, suffusing particularly authoritarian governments and financial institutions, is sometimes thought to be responsible for the ravages of Amazonia. If only governments in Amazonia would turn away from economic growth models, the argument goes, the environmental balance would be restored and prosperity would ensue. Although there is room for debate about the merits of different development strategies, the tapping of natural resources will continue in any case.
The idea that forest-clearing in the region must be halted at all costs is also unrealistic. To many in the developing world, the connection between halting deforestation and national well-being is unclear. Most of Haiti is deforested and it is one of the poorest countries in the hemisphere, but over 90 per cent of Western Europe's forests have been cleared (Williams 1990), yet inhabitants of that region enjoy some of the highest standards of living in the world. A similar situation prevails in Japan, an economic superpower. The fastest-developing countries in the third world are along the Pacific Rim, and much of their forests have been or are being destroyed. A case for conserving forests and other environments in Amazonia is made later, but it should be tied to economic development and improved standards of living for people who live within the region.
Income and wealth issues
The mounting foreign debt of developing nations is sometimes depicted as one of the "root causes" of tropical deforestation (Bramble 1987; Gradwohl and Greenberg 1988, 45; Spitler 1987). Many third world governments, it is suggested, have plundered natural resources to help pay off bank loans. Recent governments in Brazil have been accused of exploiting the Amazon rain forest to solve foreign exchange problems (Moran 1988). Some political leaders complain that, in order to meet debt payments, they are "forced" to ravage their natural resources to generate foreign exchange (Wood 1990).
But the linkage between foreign debt and accelerated development efforts has not been clearly established. Although banks in developed countries and multinational corporations are sometimes cast as the "villains" with regard to Amazonia, investments from southern Brazil are much more significant than international capital. It is true that some Amazonian resources are directly linked to the export trade, such as iron ore from Serra dos Carajás manganese from Serra do Navio in Amapá, and pulp from the Jari plantations, and domestic investment from the industrial heartland of Brazil is a major factor in many development schemes. Companies headquartered in São Paulo enjoy much greater investment exposure in Amazonia than do the World Bank or private banks in the United States, Europe, or Japan.
Investments in Amazonia from São Paulo can be viewed as a means to redistribute some of the wealth accumulated in the nerve-centre of Brazilian business. To others, the great disparity of wealth between São Paulo, with its diverse agricultural and industrial base, and relatively undeveloped Amazonia contributes to the latter's demise. São Paulo is seen as exporting pollution to Amazonia and exploiting its resources with little long-term benefit to the region. Given that forces of change in Amazonia, ranging from population growth and institutional and socio-economic factors to questions of attitudes and distribution of wealth, are likely to remain essentially the same for the foreseeable future, we focus our analysis on ways to promote the sustainable use of forests, plantations, and agricultural lands. This is not to deny the validity of efforts to change the driving forces, but rather to display options for development that can be used by societies guided by a variety of principles and forms of government.
A host of ecological issues surrounds the debate about development in Amazonia. Deforestation and its alleged role in global warming have received the most attention both in South America and around the world, but other less publicized impacts may ultimately prove more important. After reviewing the arguments for and against the role of deforestation in global warming and rainfall, we explore the environmental effects of soil erosion and floods, mining, loss of biodiversity, and hydroelectric dams.
Climatic change
Deforestation in Amazonia and other tropical regions is often claimed to contribute to the greenhouse effect, yet no firm evidence has yet emerged that the world is becoming significantly warmer (Smith et al. 1991). Even if such changes will soon be documented, it will be difficult to separate natural climatic cycles from any greenhouse effect (Mitchell, Senior, and Ingram 1989; Smith et al. 1991). In the event that the greenhouse effect takes hold, tropical deforestation will be only partly at fault (Radulovich 1990). Deforestation accounts for less than 20 per cent of greenhouse gas emissions (Flavin 1989, 13). Carbon dioxide from the burning of fossil fuels, which occurs mostly in temperate countries, is the largest component of greenhouse gases.
In addition to temperature changes, deforestation has the potential to produce adverse effects on rainfall regimes. Half of the rain that falls in Amazonia is thought to come from evapotranspiration, and continued deforestation might lead to a drier regional climate (Hecht and Cockburn 1989, 43). How much forest can be removed without affecting rainfall is not known. No evidence has yet emerged to define with any precision the role that deforestation in Amazonia has had in affecting rainfall.
Soil erosion and floods
Regardless of Amazonia's contribution to global climate change, environmental change in this basin has acute, regional implications, especially for soil and water. Soil erosion is one of the most serious threats to the sustainability of agriculture, silviculture, and forestry in Amazonia. The need to protect the soil is a major reason why perennial crops, silviculture, and properly managed pastures are among the more viable options for rural development in areas already cleared. Soil erosion and associated loss of nutrients are contributing factors in the decision of many farmers to abandon their fields and clear a fresh plot from the forest. Soil erosion can also aggravate floods. Some unusually heavy floods along the Amazon in the mid-1970s raised the spectre that deforestation in the foothills of the Andes was having a tangible impact downstream (Fowler and Mooney 1990, 106; Gentry and Lopez-Parodi 1980; Smith 1981, 122). But statistical analyses of flood peak levels do not reveal any trend to more intense flooding along the Amazon (Richey, Nobre, and Deser 1989; Sternberg 1987).
Destruction of forests along streams and some river banks is surely affecting water quality and flow on a local scale. But the vast scale of Amazonia's forests appears to be masking the impact of deforestation on smaller watersheds. Also, the variability of rainfall in different parts of the Amazon Basin can prompt premature conclusions that floods are more pronounced along the Amazon.
Corporate mining operations
Mining has become a major economic activity in Amazonia. The environmental impacts of mining operations by corporations are localized and largely insignificant since some earlier water-pollution concerns have been addressed. Settlement and development activities associated with the poles of growth generated by mining concerns can have more widespread impacts. A much publicized siltation of a lake as a result of bauxite-mining along the Trombetas River, a northern affluent of the Amazon, has been corrected. Bauxite-mining requires removal of large quantities of overlying soil, and failure to take precautions can result in sediment's washing away into nearby watercourses. At one point, 7 miles of Lake Batata near Mineração on the Trombetas had filled in with reddish-brown soil, thereby killing trees and destroying fish and wildlife habitats (Mee 1988, 279). Corrective measures have been taken by building a siltation pond, and Lake Batata is being restored.
Mineração do Norte, which operates the bauxite mine along the Trombetas, eventually replants areas scraped to gain access to the aluminium ore. Topsoil is stockpiled and then spread back once an area has been mined. Several native trees are planted to speed up restoration of the land (Gradwohl and Greenberg 1988, 173). Such recuperation efforts are costly, but Mineração do Norte is demonstrating leadership in environmental management, and technologies developed there are likely to prove useful at many other mining sites in the humid tropics.
At Carajás forest-clearing around mines is minimized, and road and rail sidings are planted to brachiaria (Brachiaria humidicola), a perennial grass from Africa (fig. 2.3). Holding ponds to deposit mining sediment have also been established by the Companhia Vale do Rio Doce (CVRD) at Carajás Outside the 400,000 ha concession granted to CVRD at Carajás forest-clearing is rampant, particularly along the 890 km railroad to Itaqui in Maranhão. Settlement is provoking a rapid retreat of the forest.
Itinerant gold-mining
In contrast to most corporate mining operations, small-scale goldmining activities in Amazonia are causing widespread ecological damage. Mercury contamination of rivers, fish, and humans as a result of gold-mining is arguably the most serious current environmental issue in Amazonia, at least from the perspective of human health. Although small-scale mining of placer gold has gone on for decades, a major gold rush began in the region in 1980 when gold prices soared (Cleary 1990). Little information, however, is available on the dimensions of the problem. Scattered reports of alarmingly high levels of mercury in human hair and certain game fish in the Madeira River system and in parts of southern Pará suggest that quicksilver, used to amalgamate gold, is working its way into the region's food webs (Braunschweiler 1991; Hecht and Cockburn 1989, 143; Malm et al. 1990; Martinelli et al. 1988).
Approximately half a million gold-miners (garimpeiros) operate in Amazonia year round. By the late 1980s, about 100 metric tons of gold were being exported annually from the Brazilian Amazon, worth some US$1 billion. For every kilogram of gold produced, at least 1.32 kg of mercury is lost to the environment. More than 100 tons of mercury are thus finding their way in to the region's ecosystems every year.
Every state in the Brazilian Amazon is currently experiencing a rapid influx of fortune-seekers. Garimpeiros are penetrating Indian reserves, national forests, and biological preserves where they pollute waters with mercury and sediment and hunt out game. Some Kayapó Indians have generated dangerously high levels of mercury, presumably from eating fish and drinking water from polluted rivers and streams (Hecht and Cockburn 1989, 143). As mercury levels rise in fish, an important source of protein in the region, the poor are especially likely to suffer. If more of the region's fish become unsafe to eat, wealthier inhabitants can more easily turn to beef, chicken, or imported fish.
Loss of biodiversity
Species extinction and the shrinking of plant and animal populations are some of the most serious consequences of habitat disturbance in Amazonia, particularly over the long term. Amazonia's forests are among the richest biomes on earth and contain a wealth of plants that could be tapped for food, industry, and medicinal uses. They also contain wild populations of many perennial crops important for commerce and subsistence (Smith et al. 1992). Wild populations of crops and, in some cases, their near relatives are increasingly sought by plant breeders for desirable traits, such as resistance to pests and disease.
Development and settlement in Amazonia are eroding wild populations of dozens of perennial crop species (Smith and Schultes 1990). The Amazon contains wild gene pools of such commercially important crops as rubber and cacao, as well as regionally important food and beverage crops, such as peach palm (Bactris gasipaes) and guarana (Paullinia cupana). Peach palm is increasingly grown for the export trade in heart-of-palm, particularly in Costa Rica, and guaraná is a popular soda in Brazil and is now exported to developed countries such as Japan and Canada. 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 marshalling of genetic resources to overcome constraints on production. Potential crops are also being lost as forests recede.
Ironically, a clean and renewable source of energy is contributing to the loss of biodiversity. Brazil, in particular, has been tapping the enormous hydroelectric potential in Amazonia since the 1960s. When oil prices increased sharply after 1973, efforts to harness the power of rivers to generate electricity increased markedly. Although the existing hydroelectric dams in Amazonia are making a valuable contribution to the region's economy by providing reliable and relatively inexpensive electricity to some areas, particularly in eastern Pará the environmental toll is yet to be fully assessed. The impact on fisheries is mixed, with some good fishing above dams but lower yields downstream in some cases (Smith et al. 1991). The loss of forest biodiversity as a result of dam construction is even more difficult to gauge. One difficulty with implementing hydroelectric projects in Amazonia is the relative flatness of much of the basin, which leaves vast areas of forest permanently inundated.
Forests 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. Conservation of forest environments, as well as of field gene banks, is thus essential for the long-term viability of many crops important for subsistence and commerce.
Another 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. Rural folk are particularly knowledgeable about the location and natural history of wild populations of crops and their near relatives. Biodiversity and cultural heterogeneity are vital to sustainable development.