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Toshie Nishizawa and Juha I. Uitto

Since its discovery, the Amazon region has been a source of fascination for humanity. In years past, adventurers flocked to the unknown and uncharted expanses seeking fame and fortune. Today, Amazonia is recognised as an important part of the global ecology and many concerned with environmental issues, often outsiders, are now trying to impede the overexploitation and destruction of this region.

The first European explorers of Amazonia were the sixteenthcentury conquistadores who came in search of El Dorado. At that time, the rain forest was only an obstacle with its great size, density, and lushness. Some three centuries later the explorer scientists began to investigate the Amazon rain forests. Among these scientists were Alexander von Humboldt, Alfred Russel Wallace, and Henry Walter Bates, who viewed the rain forest as a subject of intense scientific curiosity.

The rain forest at that time was often evaluated to have high potential, based on the knowledge gained in the temperate latitude forests, where larger trees indicated greater soil potential. However, the size of trees in the tropical regions generally does not indicate soil potential because the nutrient cycle of the region is quite different from that of the temperate regions.

Amazonia is hot, humid, and rainy, drained by a dense network of large, year-round rivers mostly debauching into the Amazon River, which alone accounts for about one-fifth of all the fresh water discharged into the world's oceans. Although there are many different ecosystems in Amazonia, most of them fall into two major groups: those of the várzea (floodplains) and those of the terra firme or tierras firmes (uplands). About one-third of the world's tropical rain forests is located in Amazonia, mostly within Brazilian territory. Those on the highly leached soils of the terra firme exhibit a number of adaptations to their oligotrophic milieu. The fertile soils of the várzea, where traditional agriculture is carried out, are rejuvenated by yearly flooding and occasionally subjected to catastrophic inundations.

North-East Brazil or the Nordeste comprises nine states and includes 18 per cent of the area and 30 per cent of the population of the country. Its development began with the arrival of the Portuguese in the sixteenth century, but it still remains one of the poorest regions in Latin America. The Nordeste is divided into three longitudinal zones, starting from the seashore: the humid zona da mata, an intermediate agreste, and the interior sertão. The latter, characterized by deficient and erratic rainfall falling on largely impervious rocks, experiences severe and frequent droughts. The scorching backlands are devoid of perennial streams, except for one exotic river, the São Francisco. The vegetation is typically drought-resistant xerophytic forest (caatinga).

The coastal humid region was originally covered by seasonal tropical rain forest. Gradual deforestation in the area has caused serious environmental problems. Development of the coastal humid region started with forest cutting of Brazil-wood for red dye. The Portuguese and other Europeans also found the climate and the fertile alluvial coastal lowlands ideal for sugar cane production. The forest on the nearby uplands was cleared for use as firewood at the sugar cane mills. Recent expansion of sugar cane production for gasohol has resulted in environmental as well as socio-economic distress.

Frontier settlements advanced into the semi-arid interior during the seventeenth century. Due to the limited natural resources, this region was not initially attractive to the settlers, but it gradually developed when cattle grazing became widespread. Despite striking contrasts, the Brazilian portion of Amazonia and the Nordeste, especially the sertão, have been intimately linked historically, demographically, and culturally.

After the middle of the nineteenth century, penetration and settlement of Brazilian Amazonia was to reflect the spatial distribution of the seringueira, or rubber tree (Hevea brasiliensia). Following the discovery of vulcanization, and at a time when the demand for rubber was increasing, the disastrous droughts of 1855 and 1866 uprooted a considerable part of the rural population of the sertão, intensifying an incipient migration to the Amazon.

When the drought struck again in 1877 and 1888, the government directed to Amazonia a good part of those flagelados (lit. "lashed"; victims of drought) who managed to reach the coast. The tattered refugees were to form the backbone of Brazil's rubber extractive industry, and put the stamp of their culture on Amazonia, a region whose Amerindian stock had been dramatically depleted following contact with Europeans, and where the Portuguese and their African slaves had never represented more than a modest, mostly urban, demographic contingent.

During the Second World War, when the Allies were cut off from the Asian sources, Brazil, pursuant to what became known as the Washington Agreements, undertook to supply them with rubber. The federal government in Rio de Janeiro turned to the Nordeste and, with appropriate propaganda, mobilized its people for a second assault into the rubber forests. During the so-called Batalha da Borracha, the ill-fated Rubber Battle, malaria and other diseases took a heavy toll on the north-easterners.

Amazonia and the Nordeste, each in its own way, have long been the cause of serious apprehension on the part of successive Brazilian governments. The former, a sparsely settled economic backwater isolated from the seat of government, has been perceived as an easy prey to foreign covetousness. The latter, a victim of endemic poverty, is a traditional exporter of people. When the backlands are smitten by catastrophic droughts, farm families are uprooted and transformed into refugees, who make their way to the humid coast. Here, a teeming, landless population, born of the plantation system, embittered and dehumanized, has been seen by nervous officials and landowners as a potential hotbed of social and political unrest.

Significantly, when the 1946 Brazilian Federal Constitution was drafted, two consecutive articles addressed the twin problems of Amazonia and the Nordeste. Article 198 mandated that "in implementing the plan to provide for protection from the effects of the socalled sêca [drought] of the Nordeste, the [federal government] shall expend annually ... an amount never inferior to three percent of its tax revenue." The same article also called for "the States included in the drought area to expend three percent of their tax revenue in the construction of dams,... and in ... assistance to their populations." According to Article 199, the federal government was enjoined to "appropriate, during at least twenty consecutive years, an amount not inferior to three percent of its tax revenues" to be applied in executing the plan for economic development of Amazonia. The same directive applied to the "States and Territories within that region, as well as to their respective MunicÍpios."

When the Programme of National Integration (PIN) was launched in 1970, construction of the Trans-Amazon and Cuiabá-Santarém highways was linked to the plight of the semi-arid backlands, afflicted by yet another drought. While the PIN stressed effective occupation of the vastness of Amazonia, it also addressed itself to the source region of the settlers, and was perceived as a means, in the words of President Medici, "to absorb the population of areas considered totally unfit for human life." Amazonia is frequently thought of, by those who eschew a deep-cutting agrarian reform, as a convenient substitute, a safety valve to absorb surplus populations, especially from the Nordeste.

With water as its most limiting resource, an option long considered for the Nordeste is the importation of this most basic resource. One possibility, examined in the early 1980s, was the transposition of water from the Tocantins River into the sertão. While not properly an affluent of the Amazon River, the Tocantins, a tributary of the Pará River, is part of Amazonia. Although the idea is not being pursued at present, it serves as a final example to underline the linkages between Amazonia and the Nordeste.

With international attention focused especially on Brazilian Amazonia, a dilemma exists between development and preservation, or conservation, of Amazonian resources. What should scientists do to resolve this dilemma? Are the traditional forest management and agriculture methods effective today?

The origin of this volume stems from an international symposium entitled The Fragile Tropics of Latin America: Changing Environments and Their Sustainable Management, organized by the Centro de Estudos Latinoamericanos of the University of Tsukuba, Japan, in May 1990. The symposium was sponsored by the University of Tsukuba, the United Nations University (UNU), and the Associação Central Nipo-Brasileira.

The symposium had as its background the recognition of the sever ity, multiplicity, and global nature of the environmental problems facing humanity on the threshold of the twenty-first century. A central theme underlying several contributions was, therefore, the dilemma confronting the countries of Latin America: on the one hand, the desire to utilize the resources of their tropical regions to improve the living standard of their citizens; on the other, a growing concern with the ecological fragility of such regions, and the realization of the urgent need to find sustainable alternatives to the prevalent models of destructive so-called economic development, which is only too often at the service of special interests. Because some aspects of environmental degradation have the potential to affect remote corners of the earth, and because the explosive growth of global, satellitebased TV coverage has stimulated worldwide interest in a "green" Earth, such preoccupations now transcend political boundaries.

Issues highlighted by the agenda of the symposium included the following: ¹ the fragility of tropical ecosystems, both humid and arid or semi-arid; ² changes wrought in the natural environment of the neotropics by human activities; ³ multiple interactions and complementarity between tropical and other regions; and 4 technological, cultural, and land tenure strategies in greater harmony with nature than those promoted by prevalent models and hence more favourable to the sustained development of tropical regions.

Some questions that surfaced during the meeting, such as the palaeoclimatic history of Amazonia, or the size and antiquity of precontact Amerindian populations, remain controversial, and it was not the editors' purpose to generate a unified point of view on any issue. The authors alone are responsible for the opinions set forth in their contributions. That said, it must be pointed out that during the period between the symposium and the publication of this volume, the papers selected for publication have gone through extensive review and revisions.

The chapters are classified into four groups. Environmental problems are discussed for Peruvian and Brazilian Amazonia, North-East Brazil, and the entire tropical Latin American region. From an ecological point of view, these regions span an enormous variety. Similarly, the myriad of subjects makes generalized conclusions difficult. The disciplines represented include meteorology, physical and human geography, plant ecology, anthropology, archaeology, and economics. Such a variety of viewpoints may help facilitate solutions to local, regional, and global environmental problems. Each chapter discusses problems unique to the tropics of Latin America.

Gilberto C. GallopÍn and Manuel Winograd outline the results of a modelling exercise containing two basic scenarios for the ecological prospects of Latin America, one based on the continuation of present trends, and another for achievement of ecological sustainability. They conclude that, based on the application of present technological and management options, it would be possible to reach sustainability for the entire region in the coming fifty years, assuming major changes in development and land use policies. However, the actual recent trends in the region give less reason for optimism.

Emilio F. Moran, emphasizing the diversity of Amazonian ecosystems, recognizes and describes the extreme environments in the region, differentiating between the oligotrophic black-water river basins and the anthropogenic forests with nutrient-rich soils. The goal is not simply to describe them, but also to move from characterization to understanding how such areas might be managed to balance the conservation and production concerns. He suggests that agricultural development should largely be confined to the latter in order to maximize benefits and to minimize harm to the environment and biological diversity.

Betty J. Meggers issues a warning on the delicacy and vulnerability of the tropical rain forest, based on archaeological evidence utilizing specialized methods of ceramic analysis. Her analysis suggests that surviving unacculturated groups preserve a way of life already established by the beginning of the Christian era, that this represents a sustainable adaptation under normal conditions, that ethnohistorical accounts exaggerate preColumbian population densities, and that several episodes of climatic fluctuation during the past two millennia seriously disrupted populations in many parts of the lowlands.

Minoru Tanaka, Akio Tsuchiya, and Toshie Nishizawa clarify the cause of low rainfall from the standpoint of tropospheric circulation. The variability of rainfall is also correlated with the sea surface temperature of the tropical Atlantic Ocean. Moreover, the differences of interannual fluctuation of rainfall between southern and northern North-East Brazil are discussed. The details of regional characteristics of rainfall are important to an understanding of the recurrent droughts and floods that contribute to the poverty cycle of the semiarid interior.

Hilgard O'Reilly Sternberg, after reviewing aspects of the aquatic and wetlands ecosystems of Amazonia, examines changes in the Amazon Basin discharge due to deforestation and the consequential influences on floodplain land use and wetland fauna. He suggests that it is reasonable to believe that the opening of Amazonia will affect the regimen of the trunk stream, but that, given the great number of variables involved, it is impossible to predict when human-induced changes will become manifest. The future remains elusive as the range of uncertainties, influenced, for instance by political and economic decisions, increases. In addition, Amazonian floodplains will be affected by a number of other factors, such as global warming and associated sealevel rise, contributing to the uncertainties.

Roberto M.C. Motta discusses the rationale for the establishment in 1967 of the Free Trade Zone of Manaus as a growth pole, and focuses on the problems of origin and recruitment of entrepreneurs and the role of state bureaucracies. The zone epitomizes some of the characteristics of Latin American economic development, including the alliance of an entrepreneurial elite, often of foreign extraction, supported by tax incentives and protective trade barriers, and a large state bureaucracy able to share in the profits of economic growth and to assert their social and political supremacy. Yet, according to Motta, the ecological and demographic peculiarities of the Amazon region seem to preclude a self-sustained process of development independent of state-supported incentives.

Mario Hiraoka studies the floodland management practices of riverine inhabitants of the Peruvian Amazon, known collectively as ribereños. The biological productivity of the floodlands is undeniable, but his findings suggest that the key to understanding the dense and permanent occupation of these areas should be sought in aboriginal resource management techniques. The ribereño production and management practices are based largely on the aboriginal patterns.

Christine Padoch and Wil de Jong describe five agroforestry systems found in the vicinity of Iquitos in north-eastern Peru. Although all begin as shifting cultivation fields, they differ greatly in species composition and richness, in intensity and length of management, in economic orientation, and in adaptation to particular ecological conditions. Their information shows that the basic traditional swiddenfallow agroforestry practices are adaptable to varying environmental and economic situations, including market access.

Miguel Pinedo-Vasquez, Daniel Zarin, and Peter Jipp outline the diverse and complex indigenous systems of forest management in a ribereño community in the lowland Peruvian Amazon. In the detailed case study, they examine the conditions for sustainable use of the forest resources in the communal monte alto areas.

Moving the focus to north-eastern Brazil, Eiji Matsumoto shows that the white sand soils are also associated with podzolic and latozoic redyellow soils in the coastal region. Sandy soil is one of the most infertile tropical soils and is distributed throughout the humid coastal North-East and Amazonia. Thus, it is very important to know the characteristics, formation, and geographical distribution of this white sand soil type. Matsumoto concludes that the soil on the tabuleiros, the low uplands of the North-East, have suffered severe modifications, especially in the development of white sand soil formations through a long, continuous deforestation process.

Ichiroku Hayashi contrasts the nitrogen content from tree leaves of the North-East with those found in Amazonian caatinga, finding those of the North-East to contain three times as much nitrogen as those in Amazonia. Caatinga is a unique vegetation that has adapted to the poor soil and cycles of drought and floods. Hayashi shows that caatinga soils contain 0.01-0.14 per cent nitrogen and 0.39-1.65 per cent carbon. The nitrogen content is very low compared with welldeveloped soils in the temperate forests. Finally, Hayashi stresses the importance of soil preservation for sustainable production of caatinga trees.

Toshie Nishizawa, Akio Tsuchiya, and Maria Magdalena Vieira Pinto estimate the response rates to water storage and water deficits, and the magnitude of tolerance of water deficits, for seventeen different caatinga tree species. As a consequence of the transformation of agricultural land-use patterns, the original caatinga has been deforested and a secondary growth of vegetation has resulted. The need for a holistic development approach benefiting both the North-East and Amazonia is demonstrated by the case of charcoal production in North-East Brazil.

Finally, Isao Saito and Noritaka Yagasaki present results from detailed field data on the changes in agriculture due to reservoir and river irrigation projects. Major problems related to irrigation are plant diseases and soil salinization. Solutions to these problems point to the necessity of an effective crop rotation system and processes to remove accumulated salt. Although their observations clearly suggest that irrigation farming has largely modified the traditional landscape and land use, they emphasize the need for continued observation of the process of change in the semi-arid interior.

The problems related to Amazonia and North-East Brazil should be approached individually as well as in a complementary fashion in order to benefit both regions. The complementary relationships of geographical characteristics of the regions are important to the reso lution of environmental problems. Moreover, perceptions and assessments of the future trends in global and/or continental scale environments are required.

The need for scientific research that strikes a balance between nature, socio-economic and political factors, and technology is demonstrated by the variety of issues raised in the present volume. Emphasis must be placed on the necessity of fieldwork for primary data gathering. Harmony between nature and human activities must be achieved in order to develop sustainable management for the fragile tropics.

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