熱帯畜産と環境保全

概要

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There are many environmental problems in animal husbandry in the tropical zone which is characterized by four climatic types : tropical rain forest climate, savanna climate, steppe climate and desert climate (W. Koppen's classification of climates). Generally speaking, these climates can be grouped into two categories based on the degree of dryness : tropical rain forest climate, and others. In this report, conservation of the land especially in dry lands and semi-dry lands (referred to as arid zone, hereafter) was discussed, with emphasis placed on Africa. Animal husbandry in the tropical zone has been practiced for many centuries mainly by nomadic tribes, in savannas. In the rain forest zone, cattle, water buffaloes, swine, poultry, etc. have been raised in subsistence farming in Africa, Latin America and South Asia for centuries. Traditional life style in the savanna enabled to maintain an equilibrium between the savanna's ecosystems and their use. Trees and bushes are important as feed for the livestock and as materials for nomadic life in the savanna as well as for the prevention of desertification. In recent years, however, the sociological and natural conditions surrounding animal husbandry have changed worldwide, mainly due to human activities and climate fluctuations. The former are related to the adaptation of modern agricultural practices and industrialization in most of the developing countries in those areas, population growth, etc. Fig. 1 shows the relationships among factors (climatic phenomena as natural conditions, and human activities as controllable conditions) related to the decrease of productive land and consequently to desertification. The main effects of human activities on animal husbandry in the tropics are as follows : 1) depletion of water sources associated with deforestation for the development of grasslands or fields for cash crop cultivation, 2) decrease of soil fertility due to inadequate soil management practices or salinity due to erosion or inadequate irrigation technology, 3) natural vegetation is disappearing due to overgrazing, wood collection for fuel and burning for cultivation. These human activities decrease the diversity of the ecosystems and disturb the succession of vegetation in the tropical zone. Climate is one of the critical factors influencing all human activities. It is an element of natural resources, affecting many economic sectors, such as agriculture, water supply, and energy consumption. There is increasing evidence that human activities are altering the earth's climate. The occurrence of a warmer climate would lead to flooding due to rising sea levels, (between 20 to 140cm for an increase of 1.5 to 4.5℃). Another danger is the trend to drought, especially in the arid zone. Furthermore, the combination of the increase in population and decrease of rainfall over extended periods of time is likely to affect severely the arid zone. It is very important for the preservation of the environment in the future to strike a balance between the increase of population and potential productivity of the area from the ecological point of view, especially in the tropics. To preserve the environment and prevent desertification in the tropical zone, it is important to develop a method to estimate the proper carrying capacity for sustainable animal husbandry along with suitable grazing methods, to harmonize agricultural practices with the natural ecosystems, in placing emphasis on traditional farming methods at the small holder level.
日本熱帯農業学会の論文
1991-06-01

著者

及川棟雄
農林水産省草地試験場

熱帯畜産と環境保全

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概要

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