16. Species interactions and community ecology in low external-input agriculture.
American J. of Alternative Agriculture, II, No. 4, 1987, pp. 160
External production inputs have contributed greatly to the remarkable increases in crop yields achieved during the past several decades. These inputs take many forms, including fertilizers, pesticides, irrigation water, various soil amendments, machinery and labour. Most of these inputs have been developed to both stimulate farm system output as well as replace materials that have been removed with the harvest. Limited concern has been given to the long-term availability of these inputs as long as farming produced a net profit. Relatively little attention was paid to understanding the biological and ecological bases of interactions occurring within the cropping system as long as such interactions were not considered detrimental to yields. But today agriculture is confronted with the need to assess the long-term sustainability of its production practices. It must consider the availability and cost of inputs and the impacts of conventional practices on the environment, food safety, and the quality of life for people involved in food production and consumption. In essence it is now as or more important to understand agroecosystems processes that promote productivity in the short term and sustain it over the long term than it is to concentrate on how much is produced.
Polyculture systems can be managed for nutrient cycling efficiency and pest and disease regulation using knowledge of multi-trophic level interactions and application of recent developments in mutualism and competition theory. A mechanistic model of additive and removal reactions on the environment is proposed as a means of studying species interactions.
The agroecosystem can be examined as a complex set of species assemblages with many levels of organization that build upon the basic understanding of the ecology of interactions at the individual organism level, emerging at the ecosystem level to understand the dynamics of what makes the entire system function. This is especially important as the understanding of ecosystem level processes of sustainable agriculture then interface with yet more complex aspects of the social and economic systems within which agroecosystems function. Eventually such an integration of social system and ecological system knowledge about agricultural processes will not only lead to a reduction in external inputs used for maintaining productivity, but will also permit the evaluation of such emergent qualities of agroecosystems on long-term environmental quality, the importance of the human element to production, the long-term effects of different farm input/output strategies, and the relationship between economic and ecological components of sustainable agroecosystem management.
It is time to redirect a large portion of the resource that have generated all of the knowledge about single-species cropping systems towards the integration of both ecological and agronomic knowledge, with a broader goal of developing the ability to quantify the ultimate mergent quality of the agroecosystem - its sustainability. This is an extremely complex process, requiring a systems-level approach and the interaction of many disciplines, but with the outcome of being able to understand where and how effective change in agriculture can come about.
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Latin America, humid tropics, lowlands, review, conference, natural resources, development strategies, protected areas, ecotourism, nontimber forest products, indigenous agriculture, pastures, plantation agriculture, plantation forestry
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