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4 Management of oligotrophic areas
There is much we can learn about the proper management of Amazonian ecosystems from the region's indigenous population, which coped with its limitations and in some cases rose above them by changing the composition of forest and soil. What we conclude from our examination of these two ecosystems is that native populations used both areas, but that they restricted their manipulations of the ecosystem to the "islands" of terra firme forest in the oligotrophic regions and focused on the eutrophic "islands" within the vaster nutrient-poor areas of terra firme.
Human populations have inhabited the upper Rio Negro for at least 6,000 years. Ceramics and anthropogenic soils have been identified in the Rio Negro, dated at 3750 BP (Clark and Uhl, 1987: 7; Saldarriaga and West, 1986; Sanford et al., 1985). The anthropogenic soils are found not in the caatinga areas but in upland tropical forests growing on oxisols, suggesting a very ancient preference for the patches of tropical forest, rather than caatinga, for occupation and agriculture.
Populations of the upper Rio Negro practise slash-and-burn agriculture, clearing areas of between 0.5 and 2.0 hectares between September and November each year. It has been observed that contemporary native populations generally avoid locating their swiddens in areas of caatinga, which through ethno-ecological taxonomies are identified as inappropriate for agriculture (Hill and Moran, 1983). Clark and Uhl (1987) estimated that in the region near San Carlos de Rio Negro, in Venezuela, only about 20 per cent of the soils were not spodosols. This extremely restricted availability of soils capable of supporting crops for even a couple of years runs counter to very old assumptions about the ease with which native populations could relocate in Amazonia and the lack of "environmental circumscription" in the basin (Carneiro, 1970). There have been no reports of nutrient-rich alfisols (terra roxa estruturada eutrófica) in the Rio Negro Basin. Galvão (1959: 24) noted another factor limiting the agricultural potential of the upper Rio Negro: the apparent avoidance of areas which required penetration into the forest and a preference for areas along river banks by horticultural populations. Chernela (1983) observed a similar preference among the Uanano, a Tukanoan population in the Vaupés, as have those who have studied the Bara Makú (Silverwood-Cope, 1972) and the Hupdu Makú (Reid, 1979). This tendency to limit territorial occupation to the river-banks may represent a compromise response to the poverty of the terrestrial ecosystem, the availability of restricted areas of fertile levees, and the importance of fisheries based on ancient territorial claims.
Similarly, flooded forests (igapós) are avoided for agriculture, given their importance for fisheries (Chernela, 1983; Clark and Uhl, 1987; Dufour, 1983). Many of the fish in Amazonian river channels enter the flooded forest during the rainy season to gain weight and to spawn (Goulding, 1980, 1981). When fishing gives poor results, the Wakuenai in Venezuela say that the fish are spawning and locate their swiddens distant from the flooded forests. Chernela (1982, 1986a) noted the same explicit avoidance of flooded forest for agriculture among the Uanano in Brazil.
The length of the cultivation period and the size of clearings is of special significance in these oligotrophic habitats. The smaller the area cleared, the easier it will be for seeds from the native vegetation to recolonize the area. The length of the cultivation period affects the levels of nutrients available to the incoming seeds and the growth rate of secondary vegetation. In black-water ecosystems, the return of the original vegetation may take over a hundred years (Uhf, 1983; Uhl et al., 1982). Uhl et al. (1982: 319) found 271 seeds per m² in an area studied at the end of the cultivation cycle, 90 per cent of them secondary successional species. It is quite likely that secondary successional species are better adapted to low levels of nutrients and can thrive where domesticated plants cannot. Succession is much slower in black-water ecosystems: above-ground biomass after three years was only 870 g/m² compared to 2,000 g/m² in areas of oxisols on upland forest. It appears that oligotrophy, as well as the flooding, are responsible for this lower level of above-ground biomass production (Uhf et al., 1982: 320). After sixty years, the above-ground biomass is only 40 per cent of that of the original vegetation (Clark and Uhl, 1987: 12; Jordan and Uhl, 1978), compared to 90 per cent of above-ground biomass in eight years on ultisols in the Peruvian Amazon (Sanchez, 1976: 351).
One of the ways in which native peoples help accelerate the recolonization of cleared areas is by planting fruit trees in the swiddens. Not only does this increase the utility of the land, but it serves to attract birds and bats, which are the principal agents of primary forest seed dispersal in the humid tropics. In a controlled experiment, areas planted in this manner had nine times the number of seeds of native trees than an area which was not planted with fruit trees at the end of the cultivation cycle. The shade of the fruit trees serves to provide the needed shade to primary tree species of slow growth, and reduces leaching of nutrients.
The lack of a marked dry season in this region would lead us to expect that burns would be of poor quality. Generally, it is the quality of the burn that determines the yield of slash-and-burn cultivation in non-volcanic areas of the humid tropics (Moran, 1981). That is clearly the case in areas with high above-ground biomass. But in areas with lower biomass, high insolation, and high albedo resulting from reflection from the white sands, the biomass dries sufficiently to burn so well that, in fact, areas of xeromorphic vegetation tend to experience burns beyond the areas cleared. Clark and Uhl (1987) documented the problem of natural burns in this habitat, where hundreds of hectares can catch fire when twenty rainless days occur. The destructive impact of fire is a real threat in this ecosystem, in contrast to other areas of the humid tropics, where fire rarely extends beyond the area cleared (or in areas scarred by logging activities). Planting follows, and is dominated by bitter manioc.
Dufour (1988) found more than a hundred varieties of bitter manioc among a Tukanoan population in the Colombian Vaupés. Very few varieties of sweet manioc were known and cultivated. Chernela (1986b) found that repeated efforts by Uanano peoples in the Vaupés of Brazil to introduce sweet cultivars of manioc failed and only bitter cultivars persisted, when she did a study of their manioc varieties. Bitter manioc resembles the native vegetation of blackwater regions by its toxic quality, which serves to conserve nutrients for the plant through reduction of herbivory. Montagnini and Jordan (1983) found that insects consumed less than 3 per cent of the tissue of bitter manioc plants due to the cyanogenetic glucosides present.
Bitter manioc cultivation solves one of the great problems of Amazonian populations: how to cultivate soils that are extremely poor in nutrients, extremely acid, and have toxic levels of aluminium. Manioc, a plant that appears to have evolved in just such areas of South America, can produce impressive yields in areas where nothing else will grow (Moran, 1973). One of the few limitations to its cultivation is its inability to withstand waterlogging, which explains why it is cultivated on higher ground. Manioc is even adapted to drought, during which it loses its leaves and goes into dormancy, gaining its leaves again with the return of soil moisture. Beans and corn, by contrast, are unable to produce a predictable crop in these nutrient-poor areas, and unable to cope with even short-term droughts. Galvão (1959: 24) noted that corn had been abandoned by the populations of the Içana and that it probably never had much importance in the Rio Negro Basin.
Bitter manioc produces the bulk of the calories for black-water basin populations. Dufour (1983) showed that among the Tukancans she studied in Colombia, 70 per cent of the energy came in the form of manioc flour and manioc bread (casabe or beijú), tapioca, manioc beer, and other forms of prepared manioc. The energy efficiency of manioc is impressive: it yielded 15.2 calories for every calorie spent on its production. Seventy percent of the production costs occur during processing. Nevertheless, the oligotrophy of the black-water regions depresses the total yields. Yields vary between 3 and 8 tons per hectare, with a mean of 4.7 (Clark and Uhl, 1987). By comparison, the world mean is 8.4 tons per hectare, and reaches 12.7 tons in Brazil. The relatively low mean harvests confirm the nutrient-poor conditions of the environment.
Clark and Uhl (1987: 19) estimated the fish productivity of the Rio NegroCasiquiare-Guaima rivers to be between 6.6 and 13.2 kg/ha/ year - one of the lowest values for any tropical basin. In Africa and Asia the mean values are 40-60 kg/ha/year and Goulding (1979) estimated the productivity of the Madeira River in Brazil at 52 kg/ha/year.
The lower mean productivity results, in large part, from the absence of some particularly large species like pirarucú or paiche (Arapaima gigas), aruanã (Osteoglossum bicirrhosum), several large species of the genus Colossoma, and several large catfishes or pimeloids (Goulding, 1979: 15). The absence of aquatic grasses in black-water rivers, an important food source for many of the larger fishes, influences the species composition of these rivers and favours smaller species. This is not to say that black-water rivers are species-poor. Goulding et al. (1988) have shown that the lower Rio Negro is among the most species-rich rivers in the world, with approximately seven hundred species. Fish species in the Rio Negro, however, are dominated by smaller species with a mean length of only 40 mm with over one hundred species of less than 30 mm length (Goulding et al., 1988: 109).
Success in fishing in black-water ecosystems depends mostly on territorial control over cataracts and flooded forest, where the fish volume is greatest. The most successful method of fishing is through the use of large fixed traps which require considerable investment in their construction and maintenance. The importance of control over the best fishing spots is evident in such a situation, and reaches a considerable level of sophistication in the Rio Negro (Chernela, 1986a; Moran, 1990). Fish was found to be a part of meals in 78-88 per cent of cases sampled by Dufour (1987: 389).
5 Management of eutrophic areas
By contrast, management of the eutrophic areas of terra firme offers the challenge of diversity. This was handled by native populations by creation of "islands of resources." They concentrated species of economic interest within close proximity to soils favourable for horticulture and favourable in locational factors, such as ease of river transportation, well-drained areas for habitational sites, and cool breezes to provide comfort and freedom from insects.
The creation of anthropogenic forests and soils solves two of the commonly mentioned problems posed by Amazonia:poor soils and species dispersal. This process need not have been conscious. The behaviour of ancestors could very well have been certified in myths and descendants continued traditions found to be favourable to their lifestyle.
For agriculture, the preferred areas were the vine forests, because of their association to alfisols. Near the villages, the population concentrated further resources by creating palm forests, bamboo forests, food/fruit-rich forests and the garbage from their settlements built up over time anthropogenic soils which would serve in the future as usable soils in previously inferior areas from an agronomic viewpoint. This is equivalent to the population creating ecotones, or transitional areas, to favour high productivity.
In eutrophic areas, cultivation of grains and other nutrient-demanding plants is possible, although this will shorten the time before fertilisation will be required. On the other hand, it makes no sense to build cities on top of these superb soils (as has been done in recent years, for example, at Tucumã, Pará) or to put them into the production of export and tree crops (as was the case in Rondônia, with cacao). Agricultural zoning of these areas will need to achieve particularly high levels of sophistication, matching the quality of the soils to the products developed. Unfortunately, much of this will have more to do with market forces than with the micro-ecological characteristics of the areas.
The eutrophic areas of terra firme can be put to intensive use. Doing so should begin with attention to the processes of environmental modification undertaken by indigenous populations, and build on these efforts. The better soils can withstand cultivation for prolonged periods of time because of their fine structure and high initial cation exchange capacity. However, fertilisation will be required for any form of continuous and intensive cultivation. The viability of continuous cultivation in these areas of terra firme is not an environmental issue per se but, rather, a political and economic one, of the government providing the conditions for access to fertilizers at competitive prices and of matching market demand to the products supplied by the areas put under cultivation. So far, for most of Amazonia, this has been poorly done. One of the few success stories has been the Japanese colony at the favourably located Tome-Açú, in which the inhabitants identified a low-weight/high-value crop early on, and which invested in technical and human resources from the outset.
Black-water ecosystems such as those found in the Rio Negro, Vaupés, and Içana represent the poorest and most limited areas of Amazonia. Aboveground biomass is lower, litterfall is poor in nutrients, decomposition is slow due to the acidity of the soils and the water, and the drainage limitations resulting from the podzolic soils contribute to making these areas a true challenge to human populations.
Selection of particularly toxic varieties of bitter manioc and hierarchical control over fishing spots further adjusted native peoples to these poor areas of Amazonia. The areas are rich in endemic species and in toxic plants with secondary compounds with great promise for advances in medicine and pharmacology. More than any others they should be protected from largescale development activities. These are important ethnic refuge areas, with low potential for intensification but high potential for specialized and more selective exploitation for genetic, pharmacological, and medical research. While the total biomass is less than elsewhere in Amazonia, the species diversity is as high, if not higher, than other phytogeographic areas of the Amazon Basin. The native populations of this region are particularly attuned to the limitations of this ecosystem and their expertise should guide land use and research in the years ahead. Their potential for medicine and pharmacology, in particular, should have highest priority, especially the caatinga and bane areas, which are too poor for most other economic uses. On the "islands" of terra firme forests, extensive forms of resource use and extraction may continue, but intensive use is out of the question except in very restricted areas.
By contrast, intensive agriculture in Amazonia is possible and should largely be restricted to the eutrophic areas, especially where there are anthropogenic forests and soils. These have demonstrated productivity and, under the right market conditions, are likely to be economical. In contrast to more virgin areas, use of these areas will have minimal significance in terms of species extinction and biodiversity, since these areas are already simplified versions of the original ecosystems, with a predominance of species of economic value. This strategy would, in turn, recommend that for the foreseeable future large areas of the Amazon be protected from further clearing until such time as, through research and conservation, their potential can be better known.
The author wishes to thank the John Simon Guggenheim Memorial Foundation for a Fellowship during 1989-1990, which permitted him to take the time to reflect upon some of the matters discussed in this paper. He also wishes to thank the Institute for Advanced Study at Indiana University for the space in which to work during the Fellowship year; and Prof. Toshie Nishizawa for the invitation to participate in the stimulating meeting at Tsukuba.
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Archaeological perspectives on the potential of Amazonia for intensive exploitation
1
Introduction
2
Evolutionary principles
3 Past and present settlement behaviour
4 Relations between várzea, and terra firme
groups
5 The impact of climatic fluctuation
6 Overcoming environmental constraints
7
Conclusion
Acknowledgements
References
Betty J. Meggers
The first European visitors were astonished by Amazonia. The lush vegetation, immense rivers, healthy climate, strange animals, and attractive people were truly a "new world," unlike anything known at home. Five hundred years later, the region continues to elicit wonder. Its biological diversity has raised the estimated number of species on the planet from three million to 30 million, and even that may be conservative. Interactions among species are intricate, life cycles are peculiar, and morphology is often exotic, especially among insects. These traits reflect the remarkably complex interaction among biota, soil, and climate, achieved during tens of millennia of biological evolution.
This successful natural configuration is now in conflict with the most successful product of cultural evolution, namely, modern industrial civilisation. We desire to replace it with the kind of landscapes we understand, to make it produce the foods we prefer and support the social and economic institutions we consider most suitable. To this end, we are converting forest to pasture, constructing roads, damming rivers, and encouraging immigration on a larger scale. But things are not working out as expected. Urban sprawl is affecting local weather. Cleared land rapidly declines in productivity and costs often exceed gains. Malaria has become a serious health hazard. The biologists warn of global disaster; the politicians say there is nothing to worry about. Who is right? How fragile are the tropics of Latin America?
We cannot answer these questions unless we recognize and rid ourselves of biases inculcated by our immersion in temperate ecosystems. We continue to judge the carrying capacity of tropical environments using temperate-zone criteria and to design projects for maximizing productivity using temperatezone models, although scientific evidence and practical experience make it increasingly evident that temperate and tropical ecosystems behave very differently. We assess the complexity of tropical forest cultures on the scale of hierarchical organization and urbanism evolved in the riverine cradles of Old World civilization, although archaeological and ethnographic evidence attests to alternative forms of social integration and population distribution. In this context, the numerous and often extensive archaeological habitation sites on the terra firme as well as along the várzea, are equated with large sedentary populations organized into stratified political entities. Similarly, the low density and high mobility of surviving indigenous groups are attributed to decimation and deculturation since European contact (Roosevelt, 1989: 31, 45; Smith, 1980: 553, 564, 566).
The temperate-zone perspective also pervades assessments of the disappointing results of development programmes. Poor planning, insufficient credit, corrupt administration, inadequate transportation, shortage of labour, defective infrastructure, and other sociopolitical and economic factors implicated in the failure of temperate-based projects are judged responsible, with the consequence that attention is focused away from potentially significant environmental and ecological factors (e.g. Collins, 1986; Schumann and Partridge, 1989).
I shall attempt to demonstrate that surviving unacculturated groups accurately depict pre-Columbian settlement behaviour and that their way of life reflects an ancient and remarkable accommodation to complex and variable conditions. In so doing, I will make two assumptions: ¹ the fundamental physical-chemical processes and evolutionary principles that have guided the transformation of life during the past five billion years remain unchanged and immune to our control; and ² our survival depends on exploiting necessary resources in sustainable ways. All organisms affect and are affected by their environments; humans differ mainly in the range of resources they use and in the elaboration of cultural mechanisms for obtaining them. Our global dominance is testimony to the superiority of cultural behaviour over nonsymbolic forms of learning, but does not justify assuming that the evolutionary processes responsible for this situation have been neutralized.By shedding another of our biases - namely, that culture is exempt from evolutionary constraints - we can take advantage of a large body of theory to discover clues for reconstructing prehistoric cultural adaptation in Amazonia, where the predominant physical remains are small undecorated fragments of pottery.
Although natural selection is the best known evolutionary process, drift is also a significant mechanism of change. Characters relevant to survival and reproduction are subject to selection, whereas those that are adaptively neutral change directionally by drift. As long as the members of a population interact socially and reproductively, behavioural and genetic variations among individuals are homogenized. If interaction is impeded, however, the resulting segments begin to diverge, in part because of different adaptive constraints and in part because of drift. The best-known cultural manifestation occurs in language, where drift accounts for gradual alterations in pronunciation, meaning, and grammar, but it also operates in other aspects of culture.
The recent history of the Panare in south-eastern Venezuela provides an excellent illustration of the process. Less than a century ago, they began expanding from their traditional territory in the Guyana highlands toward the north-west, into land vacated by the previous occupants (fig. 4.1). Dispersal along several tributaries segregated the original community into three semiisolated populations, which have begun to diverge in dialect, kinship terminology, dress, and ornament, as well as in ceremonies associated with male initiation, female puberty, and funerals (Henley, 1982: 11-14). Similar incipient linguistic and cultural differentiation has been observed among other recently separated Amazonian groups (e.g. Yanomami: Spielman, Migliazza and Neel, 1974; Campa and Machiguenga: D'Ans, 1982: 252; northern Ge: Seeger, 1981: 229-30).
Temper and firing are among the characteristics of pottery susceptible to unconscious directional change. Classifying unselected samples of fragments using uniform criteria permits recognizing distinct trends in the relative frequencies of undecorated types. All samples that can be interdigitated into a single sequence represent the same prehistoric community, termed a phase (fig. 4.2). Phases that share a specific set of decorative characteristics are assigned to the same tradition. After these communities have been identified, their settlement behaviours can be reconstructed and their population densities can be inferred. Comparing the resulting patterns with those of surviving indigenous groups makes it possible to assess whether or not the latter are representative of the pre-Columbian demographic situation.
3 Past and present settlement behaviour
Survey along the principal tributaries of the Amazon during the past fifteen years by participants in the Programa Nacional de Pesquisas Arqueológicas na Bacia amazônica (PRONAPABA) has located and sampled hundreds of archaeological sites (fig. 4.3). The resulting data permit dozens of phases to be distinguished and their settlement behaviour to be described.
Territorial configurations
The spatial distributions of habitation sites belonging to contemporary phases generally suggest contiguous territories along rivers. Along the lower Tocantins, for example, the sharp boundaries between the phases coincide with changes in the character of the river. Each zone provides different aquatic resources and requires different methods of exploitation (fig. 4.4). Similar contiguous territories have been reported among surviving indigenous communities in various parts of the lowlands, among them Akawaio River groups in westcentral Guyana (fig. 4.5).
Where steep slopes, annual inundation, and other geographical features make parts of a region unsuitable for settlement, territories are likely to be isolated by unoccupied land. Identifying this pattern archaeologically depends on more complete survey data than are available from most parts of Amazonia, but the known distributions of phases in eastern Acre (fig. 4.6) are generally comparable to the non-contiguous territories of Yukpa-Yuko communities in western Venezuela (fig. 4.7).
Village movement
Since a seriated sequence is a relative chronology, comparing the locations of sites with their chronological positions permits tracing village movement. The schematic settlement history of the Tucuruí Phase on the lower Tocantins is typical. Differences in the relative frequencies of painted decoration suggest the community was divided among two matrilocal villages, each of which moved independently and occasionally fissioned and refused. Although the sites are seldom shared, both patterns are centripetal within the territory and combine short and long moves, some to pristine and some to previously occupied locations (fig. 4.8).
The actual history of village movement during the past seventy-five years by the Mekragnoti of the upper Xingú reconstructed from interviews with informants, also incorporates long and short movements, reoccupation of several locations, and episodes of fission and fusion (fig. 4.9).
Reoccupation
Changes in the relative frequencies of the undecorated pottery types in successive levels of a stratigraphic excavation provide the basis for estimating continuity and discontinuity of occupation of a site by the same phase and for recognizing reoccupation by a different phase or phases of the same or different traditions. The procedure is exemplified by the seriated sequences of the Kiusiu and Ibare phases on the Llanos de Moxos (fig. 4.10).
Two kinds of discontinuities are evident in both seriations. First, successive levels of each excavation (connected by vertical bars at the left) are separated by one or more levels from the other excavation. This interdigitation implies that the portion of the site represented by the excavation was abandoned and subsequently reoccupied. Second, the seriated positions of some levels are contiguous, but the magnitude of the differences in relative frequencies of the principal undecorated type is equal to or greater than that between levels with disjunct positions (e.g. BE-MO-8, Levels 60-80 and 80100 cm). This situation also implies discontinuous occupation of the location sampled.
This seriation provides evidence not only for discontinuous occupation at both sites during the Kiusiu Phase, but also for reoccupation of both by the Ibare Phase. The boundary is marked by reversal of the trend in the principal undecorated pottery type and by abrupt changes in occurrence of most of the decorated types. Carbon-14 dates confirm the stratigraphic evidence for priority of the Kiusiu Phase. This pattern of reoccupation of sites by the same phase and by successive phases of the same or different traditions is characteristic throughout the lowlands.
Multiple reoccupation of the same locations is relatively common among surviving groups. For example, the Mekragnoti have moved their village thirty-six times since AD 1900. Ten of the sites had been occupied previously. Five were reoccupied once, several twice, and one three times (Gross, 1983: 439). Reoccupation of former locations is also characteristic among the Siona-Secoya and Tatuyo of eastern Colombia (Dufour, 1983: 330; Vickers, 1983: 471) and the Yanomami of southern Venezuela (Hames, 1983: 412-14). Archaeological evidence that the same location was reoccupied by phases belonging to different traditions has a modern counterpart in the reoccupation of prehistoric sites by contemporary groups (e.g. Balée 1987).
Village area
Sites of several phases in Acre vary from 3 m diameter to 8 x 15 m, comparable to the ranges of house dimensions among the Mojo, Panare, Camayurá, Kayapó, and Witoto. Along the Xingú and Tapajós, by contrast, the minimum dimensions of sites are close to the upper limit of dwellings reported ethnographically (65 x 30 m and 50 m diameter). Differences in house size are associated today with differences in the size of the domestic group, rules of marriage and residence, and other social behaviour, implying the existence of similar variation prior to European contact.
The maximum dimensions of contemporary single-house villages suggest that archaeological sites with surface extensions exceeding about 50 m in diameter or 65 m in length are the product of multiple occupation. When a site is represented by more than one stratigraphic excavation, it is often possible to correlate the levels and estimate the maximum area attributable to each episode (Meggers, 1992, fig. 5). A more detailed reconstruction of settlement history can be made from a larger number of stratigraphic excavations distributed across the site (Miller et al., 1993, figs. 69-71). Although two or more contemporary dwellings are sometimes implied, none of the episodes identified thus far covers more than a small fraction of the surface of the site.
In summary, existing archaeological evidence does not confirm the existence of large permanent settlements prior to European contact along any of the tributaries of the Amazon. Rather, it indicates that the settlement behaviour exhibited by surviving unacculturated indigenous communities, including territorial configuration, village movement, village duration, and village size, was established by the beginning of the Christian era.
