Miguel A. Altieri

Department of Environmental Science, Policy and Management

University of California, Berkeley

I. Definition Statement

II. Introduction

III. Biodiversity Features of Traditional Agriculture

IV. The Complex Nature of Traditional Farmers Knowledge

V. The Ecological services of Biodiversity in Traditional Agroecosystems

VI. Preserving the Biodiversity of Traditional Agroecosystems

VII. Using Biodiversity based Strategies to Improve Traditional Agriculture

VIII. Conclusions

Agroecosystem: A simplified natural ecosystem subjected to exploitation for purposes of food and fiber production.

Biodiversity: Diversity of microbial, animal, and plant species in an ecosystem, that display distinct ecological functions and services.

Ethnoecology: The science that studies the various forms of traditional environmental knowledge characteristic of specific ethnic groups and that translates into several forms of natural resource management.

Polyculture: The intensive growing of two or more crops either simultaneously or in sequence in the same piece of land.

Sustainable Agriculture: A form of agriculture that is environmentally sound, culturally sensitive, socially acceptable, and economically viable.

Traditional agriculture: indigenous form of ecologically based agriculture

resulting from the coevolution of local social and environmental systems.

Traditional agriculture, is an indigenous form of farming, result of the coevolution of local social and environmental systems and that exhibit a high level of ecological rationale expressed through the intensive use of local knowledge and natural resources, including the management of agrobiodiversity in he form of diversified agricultural systems.

Perhaps the greatest challenge to understanding how traditional farmers maintain, preserve and manage biodiversity is to recognize the complexity of their production systems. Today, it is widely accepted that indigenous knowledge is a powerful resourse in its own right and complementary to knowledge available from western scientific sources. Therefore, in studying such systems, it is not possible to separate the study of agricultural biodiversity from the study of the culture that nurtures it.

This chapter explains the features of biodiversity inherent to traditional agroecosystems, and the ways in which peasants apply local knowledge to manage such biodiversity to satisfy subsistence needs and to obtain ecological services. Traditional agriculture is rapidly disappearing in the face of major social, political, and economic changes; therefore, a case is made herein for the preservation of these traditional agroecosystems in conjunction with the maintenance of the culture of the local people. The conservation and management of agrobiodiversity is not possible without the preservation of cultural diversity.

A salient feature of traditional farming systems is their degree of plant diversity in the form of polycultures and/or agroforestry patterns (Chang, 1977; Clawson, 1985). This strategy of minimizing risk by planting several species and varieties of crops stabilizes yields over the long term, promotes diet diversity, and maximizes returns even with low levels of technology and limited resources (Harwood, 1979). Such biodiverse farms are endowed with nutrient enriching plants, insect predators, pollinators, nitrogen fixing and decomposing bacteria, and a variety of other organisms performing various beneficial ecological functions.

Traditional multiple cropping systems provide as much as 15-20 percent of the world food supply (Francis, 1986). Polycultures constitute at least 80 percent of the cultivated area in West Africa and predominate in other parts of Africa as well (Norman, 1979). At the same time, much of the production of staple crops in the Latin American tropics occurs in polycultures. More than 40 percent of the cassava, 60 percent of the maize, and 80 percent of the beans in the region grow in mixtures with each other or other crops (Francis, 1986).

Polycultures are very common in parts of Asia where upland rice, sorghum, millet, maize, and irrigated wheat are the staple crops. Lowland (flooded) rice is generally grown as a monoculture, but in some areas of Southeast Asia farmers build raised beds to produce dryland crops amid strips of rice (Beets, 1982).

Tropical agroecosystems composed of agricultural and fallow fields, complex home gardens, and agroforestry plots, commonly contain wel over 100 plant species per field which are used as construction materials, firewood, tools, medicines, livestock feed, and human food. Examples include multiple-use agroforestry systems managed by the Huastecs and Lacondones in Mexico, the Bora and Kayapo Indians in the Amazon basin and many other ethnic groups who incorporate trees into their production systems (Wilken, 1987).

In the Latin American tropics, home gardens are a highly efficient form of land use, incorporating a variety of crops with different growth habits. The result is a structure similar to tropical forests, with diverse species and a layered configuration (Denevan et. al., 1984). In Mexico, for example, Huastec Indians manage a number of agricultural and fallow fields, complex home gardens and forest plots containing a total of about 300 species. Small areas around the houses commonly average 80-125 useful plant species, mostly native and medicinal plants. Management of the noncrop vegetation by the Huastecs in these complex farm systems has influenced the evolution of individual plants and the distribution and composition of the total crop and noncrop communities.

In these "forest-like" agricultural systems, nutrient cycles are tight and closed. In traditional shaded coffee plantations (Inga and Erythrina) total nitrogen inputs from shade tree leaves, as well as litter and symbiotic fixation can be well over ten times higher than the net nitrogen output by harvest which usually averages 20 kg./ha/year. Clearly, the system amply compensates the nitrogen loss by harvest with a subsidy from the shade trees. In Mexico, farmers encourage the growth of native leguminous trees in cultivated fields(Wilken, 1977). From Puebla and Tehuacan south through Oaxaca, farms with light to moderately dense stands of mesquite (Prosopis spp.), guaje (Leucaena esculenta), and guamuchil (Pithecellobium spp.) are a familiar sight. Stand density varies from fields with only a few trees to virtual forests with crops planted beneath them. A slightly different practice is found near Ostuncalco, Guatemala, where rigorously pruned sauco (Sambucus mexicana) stumps dot maize and potato fields. Leaves and small branches are removed annually, scattered around individual crop plants, and then chopped and interred with broad hoes. Local farmers claim that crop quality and yields in the sandy volcanic soils of this region depend upon the annual applications of this method (Wilken, 1987).

Many traditional agroecosystems are located in centers of crop diversity, thus containing populations of variable and adapted land races as well as wild and weedy relatives of crops (Harlan, 1976). Clawson (1985), describes several systems in which tropical farmers plant multiple varieties of each crop, providing both intraspecific and interspecific diversity, thus enhancing harvest security. For example, in the Andes, farmers cultivate as many as 50 potato varieties in their fields (Brush, 1982). Similarly, in Thailand and Indonesia, farmers maintain a diversity of rice varieties adapted to a wide range of environmental conditions, and they regularly exchange seeds with each other (Grigg, 1974). The resulting genetic diversity heightens resistance to disease that attack particular strains of the crop, and enables farmers to exploit different microclimates and derive multiple nutritional and other uses from genetic variation within species.

Many plants within or around traditional cropping systems are wild or weedy relatives of crop plants. In fact, many farmers "sponsor" certain weeds in or around their fields that may have positive effects on soil and crops, or that serve as food, medicines, ceremonial items, teas, soil improvers or pest repellents. In the Mexican Sierras, the Tarahumara Indians depend on edible weed seedlings or "quelites" (Amaranthus, Chenopodium, Brassica) in the early season from April through July, a critical period before crops mature from August through October. Weeds also serve as alternative food supplies in seasons when maize or other crops are destroyed by frequent hail storms (Bye, 1981). In barley fields, it is common for Tlaxcalan farmers to maintain Solanum mozinianum to levels up to 4,500 plants/hectare, yielding about 1,300 kilograms of fruit, a meaningful input to agricultural subsistence (Altieri and Trujillo, 1987).

Farmers also derive other benefits from weeds, such as increased gene flow between crops and their relatives. In Mexico, when the wind pollinates maize, natural crosses occur with wild teosinte growing in the field borders, resulting in hybrid plants. Certain weeds are used directly to enhance the biological control of insect pests, as many flowering weeds attract predators and parasites of pests to their pollen and nectar. Other farmers allow weeds such as goosegrass (Eleusine indica) in bean fields to repel Empoasca leafhoppers, or wild Lupinus as a trap plant for the pestiferous scarab beetle (Macrodactylus sp.), which otherwise would attack corn (Altieri, 1993).

However, diversity is not maintained only within a cultivated area. Many peasants maintain natural vegetation adjacent to their fields, thus obtaining a significant portion of their subsistence requirements from habitats that surround their agricultural plots through gathering, fishing, and hunting. Such activities afford a meaningful addition to the peasant subsistence economy, providing not only dietary diversity, but also other nonagricultural resources such as firewood and medicines which support activities in the households. For the P’urhepecha Indians who live around Lake Patzcuaro in Mexico, gathering is part of a complex subsistence pattern that is based on multiple uses of their natural resources. These people use more than 224 species of native and naturalized vascular plants for dietary, medicinal, household, and fuel needs (Caballero and Mapes, 1985).

Depending on the level of biodiversity of closely adjacent ecosystems, farmers accrue a variety of ecological services from surrounding natural vegetation. For example, in Western Guatemala, the indigenous flora of the higher forests provide valuable native plants which serve as a source of organic matter to fertilize marginal soils, as leaf litter is carried from nearby forests and spread each year over intensively cropped vegetable plots to improve tilth and water retention. Some farmers may apply as much as 40 metric tons of litter/hectare each year and rough calculations indicate that a hectare of cropped land requires the litter production of10 hectares of regularly harvested forest (Wilken, 1987).

Clearly, traditional agricultural production commonly reflects a total multiple-use system of both natural and artificial ecosystems, where crop production units and adjacent habitats are often integrated into a single agroecosystem.

Ethnoecology is the study of the natural world knowledge systems of indigenous ethnic rural people. This knowledge has many dimensions, including linguistics, botany, zoology, craft skills, and agriculture, and is derived from the direct interaction between humans and their environment. In such a system, information is extracted from the environment by special cognition and perception systems that select for the most adaptive and useful information, and successful adaptations are preserved from generation to generation through oral or experimental means. Indigenous peoples’ knowledge about soils, climates, vegetation, animals, and ecosystems usually result in multidimensional productive strategies (i.e. multiple ecosystems with multiple species), and these strategies generate (within certain ecological and technical limits) the food self-sufficiency of farmers in a region (Netting, 1993).

Captivated by the ecological intricacies of ancient agricultural systems, many scientists are beginning to show interest in traditional agriculture. As they search for ways to remedy the deficiencies of modern agriculture they recognize that indigenous farmers and their systems may hold messages of hope for the future of world agriculture. After centuries of cultural and biological evolution, these farmers have developed locally adapted complex farming systems that have helped them to sustainably manage harsh environments and to meet their subsistence needs, without depending on modern agricultural technologies.

For many agricultural scientists, four aspects of these traditional knowledge systems are relevant (Altieri, 1987):

Indigenous knowledge about the physical environment is often very detailed. Many farmers have developed traditional calendars to control the scheduling of agricultural activities. Additionally, many farmers sow according to the phase of the moon, believing that there are lunar phases of rainfall. They also cope with climatic seasonality by utilizing weather indicators based on the phenologies of local vegetation.

Soil types, degrees of soil fertility, and land-use categories are also discriminated in detail. Soil types are usually distinguished by color, texture, and some times, by taste. Shifting cultivators usually classify their soils based on vegetation cover. In general, peasant soil classification types are dependent on the nature of the peasant’s relationship to the land (Williams and Ortiz Solorio, 1981). Aztec soil classification systems were very complex, recognizing more than two dozen soil types identified by origin, color, texture, smell, consistency, and organic content. These soils were also ranked according to agricultural potential and used in both land-value evaluations and rural census. Today, Andean peasants in Coporaque, Peru, recognize four main soil classes, where each soil class has specific characteristics matching the most adequate cropping system (Brush, 1982).

Many complex systems that are used by indigenous people to group together plants and animals have been well documented (Berlin et. al., 1973). The traditional name of a plant or animal usually reveals that organism's taxonomic status and researchers have found that, in general, there is a good correlation between folk taxa and scientific taxa.

Classification of animals, especially insects and birds, is widespread among indigenous farmers. Insects and related arthropods have major roles as crop pests, as causes of disease, as food, and as medicinal, in addition to their importance in local myth and folklore. In many regions of the world, agricultural pests are tolerated because they also constitute agricultural products; that is, traditional agriculturalists may consume plants and animals that would otherwise be considered pests (Brokenshaw et. al., 1980).

Ethnobotanies are the most commonly documented folk taxonomies (Alcorn 1984). The ethnobotanical knowledge of certain campesinos in Mexico is so elaborate that the Tzeltal, P'urepecha, and Yucatan Mayans can recognize more than 1200, 900 and 500 plant species, respectively (Toledo et. al., 1985). Similarly, !ko bushwomen in Botswana were able to identify 206 out of 211 plants collected by researchers (Chambers 1983), while Hanunoo swidden cultivators in the Philippines can distinguish over 1600 plant species (Grigg, 1974).

As more research is conducted, many of the traditional farming practices once regarded as primitive or misguided, are being recognized as sophisticated and appropriate. Confronted with specific problems of slope, flooding, drought, pests diseases, low soil fertility, etc., small farmers throughout the world have developed unique management systems aimed at overcoming these constraints (Klee, 1980). In general, traditional agriculturalists have met the environmental requirements of their food-producing systems by concentrating on a few principle characteristics and processes resulting in a myriad of agricultural systems that store the following structural and functional commonalties (Gliessman, 1998; Altieri and Anderson, 1986):

a.They combine high species numbers and structural diversity in time and space (both through vertical and horizontal organization of crops).

b.They exploit the full range of microenvironments (which differ in soil, water, temperature, altitude, slope, fertility, etc.) within a field or region.

c.They maintain closed cycles of materials and wastes through effective recycling practices.

d.They rely on a complexity of biological interdependencies, resulting in some degree of biological pest suppression.

e.They rely on local resources plus human and animal energy, thereby using low levels of input technology.

f.They rely on local varieties of crops and incorporate the use of wild plants and animals. Production is usually for local consumption. The level of income is low; thus, the influence of noneconomic factors on decision making is substantial.

The strength of rural people's knowledge is that it is based not only on acute observation but also on trial and error and experimental learning. The experimental approach is very apparent in the selection of seed varieties for specific environments, but it is also implicit in the testing of new cultivation methods to overcome particular biological or socioeconomic constraints. In fact, Chambers (1983), argues that farmers often achieve a richness of observation and a fineness of discrimination that would be accessible to western scientists only through long and detailed measurement and computation.

Only recently has some of this knowledge been described and written down by researchers. The evidence suggests that the finest discrimination evolves (1) from communities where the environments have great physical and biological diversity and/or (2) in communities living near the margins of survival (Chambers, 1983). Also, older community members possess greater, more detailed knowledge than younger members (Klee, 1980).

In traditional agroecosystems the prevalence of complex and diversified cropping systems is of key importance to indigenous farmers as interactions between crops, animals, and trees result in beneficial synergisms that allow agroecosystems to optimize their own soil fertility, pest control, and productivity (Altieri, 1995; Harwood, 1979; Richards, 1985).

1. By interplanting, farmers take advantage of the ability of cropping systems to reuse their own stored nutrients. The tendency of some crops to deplete the soil is counteracted by interplanting other crops that enrich the soil with organic matter. Soil nitrogen, for example, can be increased by incorporating legumes in the crop mixture, and phosphorus assimilation can be enhanced by growing crops with mycorrhizal associations.

2. The complex structure of traditional agroecosystems minimizes crop loss to insect pests through a variety of biological mechanisms. The intercropping of diverse plant species helps provide habitats for the natural enemies of insect pests as well as alternative host plants for pests. One crop may be planted as a diversionary host, protecting other more susceptible or more economically valuable crops from serious damage. The great diversity of crops grown simultaneously in polycultures helps prevent the build-up of pests on the comparatively isolated plants of each species. Where shifting cultivation is practiced, the clearing of small plots from secondary forest vegetation also permits the easy migration of natural pest predators from the surrounding forest.

3. Increasing the species and/or genetic diversity of cropping systems so that several sources of resistance are used simultaneously is a key strategy to minimize losses from plant diseases and nematodes (types of roundworms which are among the most widespread and damaging of agricultural pests). Mixing different crop species or varieties can delay the onset of diseases, reduce the spread of disease-carrying spores, and modify environmental conditions such as humidity, light, temperature and air movement, so that they are less favorable to the spread of certain diseases.

4. Many intercropping systems prevent competition from weeds, chiefly because the large leaf areas of their complex canopies prevent sufficient sunlight from reaching sensitive weed species. In general, the extent to which weeds present a problem depends on the type of crops and the proportion of the different species grown, their density, where they are planted, the fertility of the soil, and management practices. Weed suppression can be enhanced in intercrops by adding crop species that inhibit weed germination or growth. Crops such as rye, barley, wheat, tobacco and oats release toxic substances into the environment, either through their roots or from decaying plant material. Such toxins inhibit the germination and growth of some weed species such as wild mustard (Brassica spp.), and poppy.

5. Integration of animals (cattle, swine, poultry) into farming systems in addition to using them for milk, meat, and draft needs adds another trophic level to the system, making it even more complex. Animals are fed crop residues and weeds with little negative impact on crop productivity. This serves to turn otherwise unusable biomass into animal protein. Animals recycle the nutrient content of plants transforming them into manure. The need for animal feed also broadens the crop base to include plant species useful for conserving soil and water (Reijntjes et. al., 1982). Legumes are often planted to provide quality forage but also serve to improve nitrogen content of soils. Integrated crop-livestock systems usually take the form of a crop-pasture rotation in which the pasture phase "changes" the system with nutrients and organic matter and the cropping phase "extracts" the accumulated nutrients. This balances biomass and nutrient inputs and outputs.

As conversion from subsistence to cash agricultural economy occurs, the loss of biodiversity in many rural societies is progressing at an alarming rate. As peasants directly link to the market economy, economic forces increasingly influence the mode of production by emphasizing genetically uniform crops and mechanized and/or agrochemical packages. Landraces and wild relatives are progressively abandoned, becoming relics or extinct. In some areas, land scarcity (mostly a result of uneven land distribution) has forced changes in land use and agricultural practices, which in turn has caused the disappearance of habitats that formerly maintained useful non-crop vegetation including wild progenitors and weedy forms of crops (Altieri et. al., 1987).

In many parts of the world, genetic erosion is taking place at a fast rate because farmers are having to quickly change their farming systems pushed by economic, technical, and social pressures. As farmers adopt modern varieties (HYVs), farmers tend to subdivide their farming systems into commercial (mostly devoted to HYV's) and subsistence sectors where they still grow native varieties. The greatest loss of traditional varieties is occurring in lowland valleys close to urban centers and markets (Brush, 1986).

Given these destructive trends, many scientists and development workers have emphasized the need for in-situ conservation of native crop genetic resources and the environments in which they occur (Prescott-Allen and Prescott-Allen, 1981). However, most researchers believe that in-situ preservation of landraces would require a return to or the preservation of microcosms of primitive agricultural systems, an unacceptable and impracticable proposition (Frankel and Soul‚ 1981). Nevertheless, it is contended that maintenance of traditional agroecosystems is the only sensible strategy to preserve in-situ repositories of crop germplasm. Although most traditional agroecosystems are under some process of modernization or drastic modification, conservation of crop genetic resources can still be integrated into agricultural development, especially in regions where rural development projects preserve the vegetation diversity of traditional agroecosystems and are anchored in the peasant rationale to utilize local resources and their intimate knowledge of the environment (Alcorn, 1984; Nabhan, 1983).

Previous recommendations for in-situ conservation of crop germplasm have emphasized the development of a wide system of village-level landrace custodians (a farmer curator system) whose purpose would be to continue to grow a limited sample of endangered landraces native to the region (Mooney, 1983). Carefully chosen strips of five by twenty km of land at as few as 100 sites around the world where native agriculture is still practiced have been suggested to be set aside by governments to preserve crop-plant diversity (Wilkes and Wilkes, 1972). Given the increasing impoverishment and lack of income generating alternatives for rural populations in the Third World, a proposition of this kind is clearly naive since it fails to address the subsistence needs of rural populations. In many areas where the urgent short-term goal of the peasantry is survival, diverting the limited land available for conservation purposes per se might prove totally inappropriate. Design of sustainable farming systems and appropriate technologies aimed at upgrading peasant food production for self-sufficiency should incorporate native crops and wild/weedy relatives within and around production fields to complement the various production processes (Altieri and Merrick, 1987). Such efforts would ensure that preservation remains linked to the overall rural development agenda.

If biodiversity conservation is indeed to succeed among small farmers, the process must be linked to rural development efforts that give equal importance to local resource conservation and food self-sufficiency and/or market participation. Any attempt at in-situ crop genetic conservation must struggle to preserve the agroecosystem in which these resources occur (Nabhan, 1983). In the same vein, preservation of traditional agroecosystems cannot be achieved isolated from maintenance of the socio-cultural organization of the local people (Altieri, 1995). The few examples of grassroots rural development programs currently functioning in the Third World suggest that the process of agricultural improvement must (a) utilize and promote autochthonous knowledge and resource-efficient technologies, (b) emphasize use of local and indigenous resources, including valuable crop germplasm as well as essentials like firewood resources and medicinal plants, and (c) remain a self-contained, village-based effort with the active participation of peasants (Altieri, 1987). The subsidizing of a peasant agricultural system with external resources (pesticides, fertilizers, irrigation water) can bring high levels of productivity through dominance of the production system, but these systems are sustainable only at high external cost and depend on the uninterrupted availability of commercial inputs. An agricultural strategy based on a diversity of plants and cropping systems can bring moderate to high levels of productivity through manipulation and exploitation of the resources internal to the farm and can be sustainable at a much lower cost and for a longer period of time (Gliessman, 1998).

By understanding the features of traditional agriculture, such as the ability to bear risk, biological folk taxonomies, the production efficiencies of symbiotic crop mixtures, etc., many scientists have been able to obtain important information to develop agricultural technologies best suited to the needs and circumstances of specific peasant groups. While it generally lacks the potential for producing a meaningful marketable surplus, subsistence farming does ensure food security. Many scientists wrongly believe that traditional systems do not produce more because hand tools and draft animals put a ceiling on productivity. However, where productivity is low, the cause appears to be social, not technical. When the subsistence farmer succeeds in providing food, there is no pressure to inovate or to enhance yields. However, research shows that traditional crop and animal combinations can often be adapted to increase productivity when the agroecological structuring of the farm is improved and labor and local resources are efficiently used (Pretty, 1995).

As the inability of the Green Revolution to improve production and farm incomes for the very poor became apparent, the new enthusiasm for ancient technologies spearheaded a quest in the developing world for affordable, productive and ecologically sound technologies that enhance small farm productivity while conserving resources. In the Andean altiplano, development workers and farmers have reconstructed an indigenous traditional farming system that existed three thousand years ago, at an altitude of almost 4,000 meters. Indigenous farmers were able to produce food in the face of floods, droughts, and severe frosts by growing crops such as potatoes, quinua, oca, and amaranthus in raised fields or "waru-warus", which consisted of platforms of soil surrounded by ditches filled with water (Browder, 1989).

Technicians have assisted local farmers in reconstructing some 10 hectares of the ancient farms, with encouraging results, which later led to a substantial expansion of the area under warus. For instance, yields of potatoes from waru-warus can outyield those from chemically fertilized fields. Recent measurements indicate that waru-warus produce 10 tons of potatoes per hectare compared to the regional average of 1-4 tons per hectare. This combination of raised beds and canals has proven to have remarkably sophisticated environmental effects. During droughts, moisture from the canals slowly ascends the roots by capillary action, and during floods, furrows drain away excess runoff. Waru-warus also reduce the impact of temperature extremes. Water in the canal absorbs the sun’s heat by day and radiates it back by night, thereby helping protect crops from frost. On the raised beds, night time temperatures may be several degrees higher than the surrounding region. The system also maintains its own soil fertility. In the canals, silt, sediment, algae, and organic residues decay into a nutrient-rich muck which can be dug out seasonally and added to the raised beds. There is no need for modern tools or fertilizers, and the main expense is labor to dig canals and build up the platforms. This ancient technology is proving so productive and inexpensive that iitis now actively being promoted throughout the Altiplano.

In addition to the survival of the waru-warus,one of the early projects advocating this agroecological approach occured in the mid-70’s when the then existing Mexico’s Instituto Nacional de Investigaciones sobre los Recursos Bioticos (INIREB) unveiled a plan to build "chinampas" in the swampy region of Varacruz and Tabasco. Perfected by the Aztec inhabitants of the Valley of Mexico prior to the Spanish Conquest, chinampa agriculture involves the construction of raised farming beds in shallow lakes or marshes, and represents a self-sustaining system that has operated for centuries as one of the most intensive and productive ever devised by humans. Until the last several decades, it demanded no significant capital inputs yet maintained extraordinarily high yields year after year. A wide variety of staple crops, vegetables, and flowers are mixed with an array of fruit trees and bushes. Abundant aquatic life in the canals provided valuable sources of protein for the local diet (Gliessman, 1998).

Threatened by the growth of Mexico city, chinampas have nearly vanished except in a few isolated areas. Regardless, this system still offers a promising model for other areas as it promotes biological diversity, thrives without chemical inputs, and sustains year-round yields. This is how INIREB began its experiences with the transfer of the chinampa system to the lowland tropics of Mexico. Implementation and adoption of chinampas in Tabasco met with mixed success; some critics feel that no market outlets were explored for the outputs produced by the community. Nevertheless, the "raised beds" of Tabasco (or camellones chontales) are still in full operation in the swamps of this region, and apparently the local Chontal Indians have full control of them. The Chontal practice traditional agriculture, and these raised beds produce a great variety of products, which in turn has enhanced the income and food security of these "swamp farmers".

In a completely different ecoregion in the Andes, several institutions have engaged in programs to restore abandoned terraces and build new ones in various parts of the country. In the Colca Valley of southern Peru, PRAVTIR (Programa de Acondicionamiento Territorial y Vivienda Rural) sponsors terrace reconstruction by offering peasant communities low-interest loans, seeds, and other inputs to restore large areas of abandoned terraces. The main advantages of using terraces is that it minimizes risks in times of frost and/or drought, reduces soil loss, amplifies the cropping options because of the microclimate and hydraulic advantages of terraces, and thus improves crop yields. Yield data from new bench terraces showed a 43-65% yield increase in potatoes, maize, and barley compared to yields of these crops grown on slopig fields. One of the main constraints of this technology is its high labor intensity, requiring about 350-500 workers/day/hectare for initially building the terraces. Such demands, however, can be buffered when communities organize and share tasks (Browder, 1989).

In Chiloe Island, Southern Chile, a secondary center of origin of potatoes, NGO development workers are tapping the ethnobotanical knowledge of female elderly Huilliche Indians in an effort to slow genetic erosion and recover some of the original native potato germplasm. They intend to make it available to contemporary impoverished farmers, desperately in need of locally adapted varieties that can produce without agrochemicals. After surveying several agroecosystems of Chiloe, NGO technicians have collected hundreds of samples of native potatoes still grown by native farmers, and with this material and in collaboration with farmers, they have established community seed banks where more than 120 traditional varieties are grown year after year and are subjected to selection and seed enhancement. In this way, an in-situ conservation program has been initiated involving several farmers from various rural communities ensuring the active exchange of varieties among participating farmers. As more farmrs become involved, this starategy allows a continuous supply of seeds of value to resource-poor farmers for subsistence and will also provide a repository of vital genetic diversity for future regional crop improvement programs (Altieri, 1995).

A key conclusion that emerges from the relevant anthropological and ecological literature is that, when not disrupted by economic or political forces, the indigenous mode of production generally preserves rather than destroys biodiversity and natural resources. In fact, in any particular region, capitalist development through promotion of large-scale, commercial agriculture is bound to affect natural resource conservation more than some of the existing traditional systems. In fact, many studies have proven that many traditional systems are highly sustainable and productive, offering an alternative to the capital intensive agriculture currently promoted by many development agencies. Besides using crop diversity, traditional farmers use a set of practices that cause minimal land degradation. These include the use of terraces and hedgerows in sloping areas, minimal tillage, mulching, small field sizes, and long fallow cycles (Grigg, 1974; Brush, 1980; Richards, 1985; Netting, 1993). It is clear that the peasant strategy towards complexity has a deep ecological rationale, as the kinds of agriculture with the best chance to endure are those that deviate least from the diversity of the natural plant communities within which they exist (Altieri, 1995; Gliessman, 1998).

It is not a matter of romanticizing subsistence agriculture or considering development per se as detrimental. The intention is rather to stress the value of traditional agriculture in the preservation of biodiversity, native crop diversity and the adjacent vegetation communities (Toledo, 1980). Basing a rural development strategy on traditional farming and ethnobotanical knowledge not only assures continual use and maintenance of valuable genetic resources but also allows for the diversification of peasant subsistence strategies (Alcorn, 1984; Caballero and Mapes, 1985), a crucial issue in times of economic uncertainty.

In addition, the study of traditional agroecosystems and the ways in which peasants maintain and use biodiversity can speed considerably the emergence of agroecological principles, which are greatly needed in order to develop more sustainable agroecosystems and biodiversity conservation strategies both in the industrial and developing countries.

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