Brazil

Emanuel Adilson Souza Serrão and Alfredo Kingo Oyama Homma

Deforestation of the Brazilian Amazon, the largest tropical forest reserve on the planet, has attracted worldwide attention in recent years. The environmental disturbances have been claimed to be a result of agricultural developments over the past 3 decades. Because of the increasing rural and urban population demands for food and fiber and the need for environmental conservation and preservation, however, land in the Brazilian Amazon must be used on a sustainable basis. The search for a compromise between ecologic and population demands is a major challenge to those in governmental, nongovernmental, and private institutions. This profile addresses the questions of agricultural sustainability in the Brazilian humid tropics by analyzing the important present and potential land uses and by considering their sustainabilities and potential for improvement and expansion.

BASIS FOR SUSTAINABILITY ANALYSIS OF AMAZONIAN AGRICULTURE

Sustainability must be the basis for analysis and implementation of agricultural land use alternatives for the Brazilian Amazon, but

Emanuel Adilson Souza Serrão is a research agronomist and Alfredo Kingo Oyama Homma is a socioeconomist at the Centro de Pesquisa Agroflorestal da Amazônia Oriental (Center for Agroforestry Research of the Eastern Amazon), Empresa Brasileira de Pesquisa Agropecuária (Brazilian Enterprise for Agricultural Research), Belém, Brazil.



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Sustainable Agriculture and the Environment in the HUMID TROPICS Brazil Emanuel Adilson Souza Serrão and Alfredo Kingo Oyama Homma Deforestation of the Brazilian Amazon, the largest tropical forest reserve on the planet, has attracted worldwide attention in recent years. The environmental disturbances have been claimed to be a result of agricultural developments over the past 3 decades. Because of the increasing rural and urban population demands for food and fiber and the need for environmental conservation and preservation, however, land in the Brazilian Amazon must be used on a sustainable basis. The search for a compromise between ecologic and population demands is a major challenge to those in governmental, nongovernmental, and private institutions. This profile addresses the questions of agricultural sustainability in the Brazilian humid tropics by analyzing the important present and potential land uses and by considering their sustainabilities and potential for improvement and expansion. BASIS FOR SUSTAINABILITY ANALYSIS OF AMAZONIAN AGRICULTURE Sustainability must be the basis for analysis and implementation of agricultural land use alternatives for the Brazilian Amazon, but Emanuel Adilson Souza Serrão is a research agronomist and Alfredo Kingo Oyama Homma is a socioeconomist at the Centro de Pesquisa Agroflorestal da Amazônia Oriental (Center for Agroforestry Research of the Eastern Amazon), Empresa Brasileira de Pesquisa Agropecuária (Brazilian Enterprise for Agricultural Research), Belém, Brazil.

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Sustainable Agriculture and the Environment in the HUMID TROPICS few analyses have provided insight (Alvim, 1989; Fearnside, 1983, 1986; Homma and Serrão, In preparation). The possibility of developing sustainable agriculture in the Amazon depends on its permanence in an area and on increasing land and labor productivity standards, thereby reducing the pressure for more deforestation. This concept of sustainability implies an equilibrium in time among agronomic and/or zootechnical, economic, ecologic, and social feasibility. Equilibrium is frequently fragile in Amazonian agricultural systems, and no agricultural land use system in the Amazon meets all four of these prerequisites for sustainability at highly satisfactory levels. The land use systems analyzed here were selected because of their present and potential importance characterized by their scale of utilization (for example, total area used and number of farmers involved), the types of farmers that use each system, its economic importance, possibilities for future markets, environmental implications, and possibilities for agroindustries. Characterization also includes technological patterns (for example, land and labor use intensity, input utilization, adoption of technology, product processing, and management practices) and productivity patterns (for example, maintenance of productivity, productivity increase potential, and relationship between productivity and the environment). More than enough land has already been deforested for agricultural development in the Amazon. From a technical point of view, by using only about 50 percent of the already deforested land and other less fragile ecosystems, such as well- and poorly drained savannahs and alluvial floodplains, it is possible to produce sufficient amounts of food and fiber to meet the demands of the region's population for the next decade at least. Future agricultural production in the Amazon will depend on higher levels of land use intensification with decreasing rates of deforestation (the decreasing deforestation brought about as a result of increasing national and international pressures for environmental conservation, increasing local environmental ethics, and increasing population density and, consequently, higher land prices). Productivity and sustainability must be the foundation for future agricultural development. In this scenario, agricultural technology will play the major role. THE BRAZILIAN HUMID TROPICS The Brazilian humid tropics encompasses the geographic area that has been named, for development purposes, the legal Amazon, an area of about 510 million ha, corresponding to 60 percent of Brazil's national territory.

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Sustainable Agriculture and the Environment in the HUMID TROPICS Although there has been a significant increase in population density in the Amazon during the past 3 decades, only about 10 percent (16 million) of Brazil's population inhabits this immense region (Brazilian Institute of Geography and Statistics, 1991). This population is unevenly distributed throughout the region in densely populated nuclei separated by extensive, virtually uninhabited land. The average population density in the Amazon is about 2.7 inhabitants per 100 ha. Presently, 61 percent of Brazil's population in the northern region lives in urban areas, and a significant portion of that population lives on the outskirts of Belém, Manaus, and other major cities. The region's population is expected to grow moderately in the next 2 decades, increasing from the present 16 million people (in 1990) to 26 million by 2010 (a 62 percent increase). This means that the Amazon population at the end of the first decade of the next century will be 13 percent of the country's population compared with the present 11.4 percent (Medici et al., 1990; Superintendency for the Development of the Amazon, 1991). In general, per capita income in the Amazon region is very low, equivalent to US$1,271 (1991), which represents 51.5 percent of Brazil's per capita income (Superintendency for the Development of the Amazon, 1991). The Environment The Amazon hydrographic basin covers about 6 million km2 and is considered the largest river network in the world. It is navigable along 20,000 km of waterways and has a total watershed area of about 7.3 million km2. This network includes muddy-water rivers that originate in alluvial soil regions. The rivers deposit organic and inorganic sediments along their paths, forming floodplains locally called várzeas. These floodplains are rich in nutrients and organic matter and have a high potential for agricultural development. The Amazonian climate is predominantly hot and humid and often presents conditions for high levels of biomass production. Relatively large amounts of solar radiation reach the earth's surface throughout the year. Average temperatures vary between 22° and 28°C, the daily variations being considerably higher than seasonal variations. Relative humidity tends to be high in most of the region, varying from about 65 to 90 percent. Total annual rainfall varies between 1,000 and over 3,000 mm. The rainy season is from December and January through May and June in most of the region, and a dry season occurs during the rest of the year. The vegetation that covers the Amazon is related to climatic con-

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Sustainable Agriculture and the Environment in the HUMID TROPICS ditions, but rain forests are the predominant ecosystem. The main types of vegetation are dense upland forests, open upland forests, savannah-type vegetation that includes well- and poorly drained savannahs, and alluvial floodplain (várzea) vegetation (Nascimento and Homma, 1984). Dense upland forests, which have high levels of biomass and include the tallest tree species, occupy about 50 percent of the legal Amazon. Open forests, which have a considerably smaller biomass volume, shorter trees, and more palm species and lianas, occupy about 27 percent of the region. Well-drained savannah vegetation (cerrado) with different arboreal and herbaceous gradients occurs in extensive areas in the states of Amapá and Roraima and occurs less extensively in areas in other parts of the region, where the forest is interrupted. About 80 percent of the legal Amazon (430 million ha) is upland, nonflooding area. The remaining 20 percent (70 million ha) is floodable area (Nascimento and Homma, 1984). Nascimento and Homma (1984) estimate that approximately 88 percent (450 million ha) of Amazonian soils are dystrophic (acidic and low in fertility) and that the remaining 12 percent (50 million ha) is eutrophic (less acidic and relatively high in fertility). Of the latter, 25 million ha is upland soils, and 25 million ha is floodable soils. Macroecologic Units At least one attempt (Nascimento and Homma, 1984) has been made to combine natural resources information by superimposing climate, soil, and vegetation maps to locate macroecologic units suitable for agricultural development, conservation, and preservation in the Amazon (Table 1). These macroecologic units and their distributions could be useful for making the first approximations of agroecological zoning in the Amazon. AGRICULTURAL DEVELOPMENT To evaluate agricultural sustainability in the Brazilian Amazon, it is important to examine agricultural development chronologically and from the physical and economic viewpoints. Chronological Agricultural Development The history of the development of the Amazon is pinpointed with ill-fated booms, badly oriented development projects, some partial successes, and ecologic and social mishaps (Norgaard, 1981).

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Sustainable Agriculture and the Environment in the HUMID TROPICS TABLE 1 Macroecological Units of the Legal Amazon   Mapping Unit     Climate Vegetation Soil Approximate Area (million ha) Percentage of Total Legal Amazon Area Afi Dense forest Upland dystrophic 60.0 11.66     Floodplain eutrophic (várzea) 7.9 1.53     Floodplain dystrophic 4.5 0.88   Open forest Upland dystrophic 13.0 2.53     Floodplain eutrophic (várzea) 0.8 0.15   Open native grassland Upland dystrophic 0.2 0.04     Floodplain eutrophic (várzea) 1.0 0.21   Subtotal   87.4 17.00 Ami Dense forest Upland eutrophic 5.2 1.02     Upland dystrophic 116.4 22.64     Floodplain dystrophic (várzea) 11.3 2.19     Floodplain dystrophic 13.7 2.66   Open forest Upland eutrophic 12.7 2.48     Upland dystrophic 16.5 3.22     Floodplain eutrophic (várzea) 2.3 0.45   Savannah (cerrado) Upland eutrophic 1.0 0.20     Upland dystrophic 12.2 2.37     Floodplain eutrophic (várzea) 0.5 0.10   Open native grassland Upland eutrophic 1.0 0.19     Upland dystrophic 10.9 2.11     Floodplain eutrophic (várzea) 4.0 0.77     Floodplain eutrophic 3.1 0.60   Subtotal   210.8 41.00

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Sustainable Agriculture and the Environment in the HUMID TROPICS Awi Dense forest Upland eutrophic 1.5 0.30     Upland dystrophic 27.7 5.38     Floodplain eutrophic (várzea) 0.8 0.16     Floodplain dystrophic 1.9 0.37   Open forest Upland eutrophic 5.6 1.09     Upland dystrophic 80.8 15.72     Floodplain eutrophic (várzea) 0.25 0.05     Floodplain dystrophic 7.4 1.45   Savannah (cerrado) Upland eutrophic 3.4 0.67     Upland dystrophic 66.0 12.83     Floodplain dystrophic 5.1 1.00   Open native grassland Upland eutrophic 0.8 0.16     Upland dystrophic 11.7 2.28     Floodplain dystrophic 2.8 0.54   Subtotal   215.75 42.00 Total     513.95 100.00 SOURCE: Adapted from Nascimento, C. N. B., and A. K. O. Homma. 1984.Amazônia: Meio Ambiente e Tecnologia Agrícola. Documento 27. Belém, Brazil: Brazilian Enterprise for Agricultural Research–Center for Agroforestry Research of the Eastern Amazon.

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Sustainable Agriculture and the Environment in the HUMID TROPICS Even though mining and energy-producing projects have emerged as the main development thrusts in the Amazon, associated development activities, including agricultural activities, usually follow in their wake (Smith et al., In press-a,b). For this reason, some important historical aspects of agricultural development in the Amazon that will pave the way to a better understanding of the analysis of agricultural sustainability given later in this profile are presented here. From the early seventeenth to the early twentieth centuries, agricultural development in the Amazon depended on extraction activities in existent forests. Even today, extrativismo (extractive land use) plays a very significant role in the regional economy, mainly because of the commercialization of timber, heart of palm, rubber, and Brazil nuts, among other forest products, in addition to hunting and fishing. More modern agricultural and livestock development began to take place toward the end of the first quarter of the twentieth century along the relatively fertile várzea floodplains, not only because of the favorable conditions they offered for agricultural production but also because of favorable river transportation along the Amazon River network. By the mid-1950s, the várzea development gave way to the up-land terra firme development when road construction started criss-crossing the region. This phase was characterized by extensive agricultural development where forest slash-and-burn activity was the main feature. Road construction was then considered synonymous with progress and made the region attractive to immigrants. Cattle raising, shifting (slash-and-burn) subsistence agriculture, and timber exploration are now the dominant features of upland development (Homma and Serrão, In preparation). Physical and Economic Agricultural Development To analyze agricultural sustainability in the Brazilian humid tropics, it is important to have an idea of how and where agricultural development has taken place. More detailed descriptions are given in the literature (Homma, 1989; Homma and Serrão, In preparation; Nascimento and Homma, 1984; Serrão and Homma, In press). From 1900 to 1953, extraction activities in the Amazon were greater than crop farming and cattle raising, contributing 50 percent of the agricultural gross national product (AGNP) in the region mainly because of the major influence of rubber extraction in the Amazon economy (Homma, 1989). After the mid-1940s, the decline of extraction began with the dissemination of jute cultivation along the Amazon várzea

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Sustainable Agriculture and the Environment in the HUMID TROPICS floodplains and with the expansion of black pepper agriculture in eastern Pará. From 1965 to 1971, for the first time, crop farming and cattle raising surpassed extraction activities. The predominance of crop farming and cattle raising over extraction activities was observed in the 1970s and continues to the present. Most of those involved with extraction activities turned to crop farm- Agricultural Development in the Brazilian Amazon 1616–1750 Agricultural activities were primarily the extraction of exotic herbs and medicinal plants as well as spices, especially cacao 1750–1822 Extraction activities and some small-scale expansion of shifting subsistence agriculture and cattle raising activities 1850–1912 Rubber extraction mostly displaced the then prevalent agricultural activities to meet international demand 1927 Henry Ford launched the first and largest private domesticated rubber plantation in Brazil, but the lack of agronomic sustainability led to the enterprise's failure; it was transferred to the Brazilian government in 1945 1932 Japanese immigrants introduced and expanded jute crop agriculture in the floodplains along the upper and mid-Amazon River 1933 Japanese immigrants introduced black pepper, an important source of revenue for the state of Pará 1939–1945 Rubber regained its importance as a strategic product as a result of the Washington Agreement signed in 1942, which guaranteed the supply of natural rubber to the Allied Forces (rubber tree plantations in southeastern Asia were controlled by the Japanese) 1953 Rubber production was greatly stimulated through several government development programs to meet the national rubber demand, but without success 1966 Operation Amazon gave ranchers incentives to raise cattle on pastureland that replaced forestland 1967 The Jari Agroforestry Project on the banks of the Jari River on the Amapá-Pará border was initiated; after a series of technical and political ups and downs, the project was sold to a consortium of Brazilian entrepreneurs in 1982 1970 The federal government launched aggressive developmentthrough- colonization programs along recently built roads

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Sustainable Agriculture and the Environment in the HUMID TROPICS ing and cattle raising, which was also the case with those who came with the migratory flux in that same period. Shifting agriculture has become the major activity of a large number of small farmers. It is characterized by low levels of technology and low productivity, even though it is a reasonably good alternative for the partial recovery of soil fertility and for the recovery of weed-, 1970s An important diversification process took place with the expansion and/or introduction of economically important crop production systems of black pepper, coffee, African oil palm, papaya, passion fruit, and melon, among others; this process continued into the 1980s with the expansion of citrus, coconut, Barbados cherry, cupuaçu, and other, less important crops Early 1970s Subsistence agriculture, which was initially carried out in the várzea floodplain areas, turned to the upland areas along the recently built roads and through the shifting agricultural systems 1976 Intensive cacao production began to be stimulated by the federal government through the Cacao Development Program 1980 The federal government set up the Grande Carajás Program in which the agricultural development component followed in the wake of the mineral exploration component 1987 Pressed by national and international ecologic movements and the autonomous rubber tappers movement, the federal government created the Extractive Allocation Project 1980s The magnitude and intensity of deforestation and burning in the Amazon generated a great concern in national and international scientific communities and governments; this movement was stirred up in 1988 when rubber tapper leader Chico Mendes was assassinated because of land tenure conflicts 1989 The federal government conceived and created Our Nature Program; along with it, the Brazilian Environmental and Renewable Natural Resources Institute (IBAMA) was created in an attempt to, among other things, control deforestation and help to promote ecologically sustainable development in Brazil, particularly in the Amazon

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Sustainable Agriculture and the Environment in the HUMID TROPICS pest-, and disease-infested areas, because of the accumulation of nutrients in the biomass during the various fallow periods imposed on cultivated tracts of land. However, this land use system has imposed substantial losses of forest resources and is subject to increasing socioeconomic instability when the population density increases. Extensive cattle raising systems have been predominant in certain areas of the Amazon where natural grassland ecosystems (such as well-and poorly drained savannah grasslands and floodplain grasslands) are available and on the pasturelands that have replaced forests over the past 3 decades. Supported by tax incentive programs, this sector has been responsible for most of the deforestation in the Brazilian Amazon region (Browder, 1988). The majority of the region's most important transformations in the primary (agricultural production) sector started in the 1960s with the expansion of the agricultural frontier, mostly as a result of tax incentive policies and the construction of important highways, which favored the development of colonization programs and the installation of large agricultural projects, the bulk involving cattle raising. Cattle raising expansion began in the mid-1960s because of the low utilization levels of labor, which was scarce at the time, and the abundance of land. This most recent regional agricultural development phase is characterized by accelerated, large-scale, and aggressive exploration of natural resources. This replaces the humid tropical forests with land use systems with generally low ecologic and socioeconomic efficiencies (cattle raising projects and shifting agriculture) or large-scale predatory “industrial” extraction activities such as those for timber and heart of palm (Euterpe oleracea). Because of the environmental degradation that they cause, these land use systems have been severely criticized (Mahar, 1989). During the past 3 decades, despite their still modest acreage in relation to shifting agriculture and cattle raising, perennial crop plants such as African oil palm (Elaeis guineensis), rubber (Hevea spp.), cacao (Theobroma cacao), Brazil nut (Bertholletia excelsa), guaraná (Paullinia cupana), and semiperennials such as black pepper (Piper nigrum) and, more recently, urucu (Bixa orellana) have become increasingly important. Special government financing programs such as the Cacao Development Program, PROBOR (the Natural Rubber Production Incentives Program), as well as a number of credit lines during the 1970s, give farmers incentives to expand these crops. Today, there are different forms of agricultural production in the Amazon because of different environmental and basic infrastructural peculiarities. These range from extraction activities in remote areas

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Sustainable Agriculture and the Environment in the HUMID TROPICS FIGURE 1 Effects of population density on land use in the Brazilian humid tropics. LF, Long fallow; SF, short fallow. Source: Adapted from Serrão, E. A. S., and J. M. Toledo. In press. Sustaining pasture-based production systems in humid tropics. In Development or Destruction: The Conversion of Tropical Forest to Pasture in Latin America, S. B. Hecht, ed. Boulder, Colo.: Westview. with low population densities to extensive cattle raising, or from agricultural activities in recently opened frontier lands to those in long-occupied areas. Land use intensification for forest product exploitation, traditional crop production, and cattle production has been influenced by population density and land prices (Figure 1). In areas with low population densities, where land prices are normally low, extraction activities, such as those for rubber, timber, and Brazil nuts, coexist with shifting agricultural systems with long fallow periods and extensive livestock activities (Serrão and Toledo, In press). In areas with medium population densities, land prices are higher, which brings about less extraction activity, shifting agricultural systems with shorter fallow periods, more intensive cattle production, and perennial cropping activities. In areas with high population densities, intensive annual and perennial cropping is expanded, subtracting from activities in areas previously devoted to extraction, shifting agriculture, and extensive cattle raising. Land prices become even higher and intensive agricultural practices are predominant. At this stage, more

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Sustainable Agriculture and the Environment in the HUMID TROPICS need for maintaining biodiversity and the slow vegetative growth cycles of forest timber resources will restrict timber extraction to some selected areas. Increasing prices of timber products will induce production on timber plantations, the only alternative to meet future demands because of population increases. Future plantations will also be needed to meet the future demands of the paper and cellulose industries. Ecologically, these plantations will be justified as a means of absorbing atmospheric carbon. Integrated systems to increase agronomic and ecologic sustainabilities will be stimulated even if economic sustainability is marginal. Within this context, agrisilvopastoral systems are included. Intelligent, appropriate combinations will be proposed. Their implementation will largely be limited by market dimension, management, and the availability of technology. Other activities will probably be implemented. Fish production—whether through cultivation of native and exotic fish under controlled conditions or through the replenishing of rivers and lakes—and domestication of high-value native wildlife will be developed. With the present technological standards of agriculture in the Amazon, the possibilities for high levels of agronomic and ecologic sustainability are reduced. Socioeconomic limitations for sustainable agriculture are also important barriers, since agronomic and ecologic sustainability is generally economically infeasible. To maintain productivity gains, maintenance of sustainability requires continuous investments in research. Environmental constraints will always be a challenge to research in the search for agricultural sustainability in the humid tropics. In the long run, the comparative advantages of abundance of natural resources and unqualified labor will be abandoned. It is probable that increasing technological advances and labor qualification will be the main supports of future agricultural activities. Despite these limitations, there are ample possibilities for increasing agricultural sustainability in the Brazilian humid tropics without having to incorporate new segments of forest and within global perspectives of sustainability. Continuous technological development within the farmer's capacity to accompany technical progress is indispensable to implementing production systems that are more compatible with agronomic and ecologic sustainability. Economic viability must be within short- and long-term horizons, preferably without any protectionist measures. Economic profitability is a key factor for agricultural sustainability in the Amazon. Rural poverty will not allow high ecologic sustainability.

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Sustainable Agriculture and the Environment in the HUMID TROPICS Even in the case of cattle raising activities, the adoption of fewer ecosystem-degrading processes will depend on higher values of cattle-related products. However, an awakening of society's awareness and the formation of a new ethic in relation to profitability, which includes environmental costs, are necessary. From this analysis of traditional and presently developing land use systems in the Brazilian humid tropics, it is clear that some land use systems are more appropriate for implementation. Because these have demonstrated moderate to high levels of sustainability and high expansion potential for mid- and long-term agricultural development, and on the basis of their favorable present and potential sustainability features, priority for expansion and research support should be given to the following land use systems: Nippo-Brazilian-type agroforestry, Integrated pasture-based (agrisilvopastoral) systems, Native forest timber extraction with sustainable management, Reforestation for timber and cellulose production, and Várzea floodplain agriculture. Technological and educational deficiencies are the main factors limiting farmers in their attempts to practice agriculture that allows higher levels of sustainability in the Amazon. Research is not the panacea for meeting high levels of agricultural sustainability as defined here. The reduced success of most agricultural enterprises in the Amazon is not so much due to the productive potential of the land as it is due to deficient social, economic, and infrastructural conditions; lack of stable and coherent agricultural policies; and fluctuations in the prices of agricultural products. More investments are needed in the rural environment to improve quality of life, thus avoiding (or minimizing) a rural exodus and continuous migration to new areas. REFERENCES Alcântara, E. 1991. A ciência afasta o perigo do desastre global. Rev. Veja, São Paulo 24(41):78–84. Allegretti, M. H. 1987. Reservas Extrativistas: Una Proposta de Desenvolvimento da Floresta Amazônica. Curitiba, Brasil: Instituto de Estudos Amazônicos. Allegretti, M. H. 1990. Extractive reserves: An alternative for reconciling development and environmental conservation in the Amazon. Pp. 252–274 in Alternatives to Deforestation: Steps Toward Sustainable Use of the Amazon Rain Forest, A. B. Anderson, ed. New York: Columbia University Press. Alves, E. 1988. Pobreza Rural no Brasil: Desafios da Extensão e da Pesquisa.

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Sustainable Agriculture and the Environment in the HUMID TROPICS Brasilia: Companhia de Desenvolvimento do Vale do Rio São Francisco. Alvim, P. T. 1978. Floresta Amazônica: Equilibrio entre utilização e conservação. Ciéncia Cultura 30(1):9–16. Alvim, P. T. 1989. Tecnologias apropriadas para a agricultura nos trópicos úmidos. Agrotrópica 1(1):5–26. Alvim, P. T. 1990. Agricultura apropriada para uso contínuo dos solos na região Amazônica. Espaço, Ambiente Planejamento 2(11):1–71. Anderson, A. B. 1989. Estratégias de uso da terra para reservas extrativistas da Amazônia. Pará Desenvolvimento 25:30–37. Anderson, A. B. 1990. Extraction and forest management by rural inhabitants in the Amazon estuary. Pp. 65–85 in Alternatives to Deforestation: Steps Toward Sustainable Use of the Amazon Rain Forest, A. B. Anderson, ed. New York: Columbia University Press. Anderson, A. B., A. Gely, J. Strudwick, G. L. Sobel, and M. G. C. Pinto. 1985. Um sistema agroflorestal na várzea do estuário Amazônico (Ilha das Onças, Munícipio de Barcarena, Estado do Pará). Acta Amazon. Manaus 15(Suppl.):195–224. Associação das Indústrias de Madeiras dos Estados do Pará e Amapá. 1989. Comércio Exterior: Produtos Exportados Pelo Estado do Pará. Fonte, Brasil: Carteira de Comércio Exterior, Banco do Brasil. Bastos, et al. 1986. O estado atual de conhecimentos de clima da Amazônia brasileira com finalidade agricola. Pp. 19–36 in Simpósio do Trópico Úmido I, Vol. VI, Anais. Belém, Brazil: Brazilian Enterprise for Agricultural Research–Center for Agricultural Research of the Humid Tropics. Brazilian Enterprise for Agricultural Research. 1980. Centro de Pesquisa Agropecuária do Trópico Úmido, Belém, Projeto Melhoramento de Pastagem da Amazônia (PROPASTO). Relatório Técnico 1976/79. Belém, Brazil: Center for Agricultural Research of the Humid Tropics. Brazilian Enterprise for Agricultural Research. 1990. Relatório Técnico Anual do Centro de Pesquisa Agropecuária do Trópico Úmido. Belém, Brazil: Center for Agricultural Research of the Eastern Amazon. Brazilian Institute of Geography and Statistics. 1981. Anuário Estatístico do Brasil. Rio de Janeiro: Brazilian Institute of Geography and Statistics. Brazilian Institute of Geography and Statistics. 1991. Anuário Estatístico do Brasil. Rio de Janeiro: Brazilian Institute of Geography and Statistics. Brazilian Institute of Space Research. 1990. Avaliação da Alteração da Cobertura Florestal na Amazônia Legal Utilizando Sensoriamento Remoto Orbital. São Paulo: Brazilian Institute of Space Research. Browder, J. O. 1988. The social costs of rainforest destruction: A critique and economic analysis of the “hamburger debate.” Interciencia 13:115–120. Burger, D., and P. Kitamura. 1987. Importância e viabilidade de uma pequena agricultura sustentada na Amazônia oriental. Tübinger Geog. Studien 95:447–461. Buschbacher, R., C. Uhl, and E. A. S. Serrão. 1988. Abandoned pasture in eastern Amazônia. II. Nutrient stocks in the soil and vegetation. J. Ecol. 76:682-699.

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