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Encyclopedia Of Animal Science - E

Từ điển khoa học động vật vần E | Ecology and Environment Issues John A. Milne The Macaulay Institute Aberdeen U.K. INTRODUCTION The impact of domesticated livestock on the functioning of ecosystems is the focus of this article. Historically there have always been positive and negative impacts on the functioning of ecosystems particularly those that include humans but the extent of the impacts has increased as human and livestock populations have increased. In the last century the application of science to animal production systems together with an increase in the demand for food and other products from livestock has led to an intensification of livestock systems. Intensification has been particularly the case for pigs and poultry and to an increasing extent for dairy cow systems. This has led to impacts on the functioning of ecosystems containing soil as a component and on aquatic ecosystems mainly through the housing of livestock in large numbers and the need to dispose of excreta. Intensification of dairy beef and sheep grazing systems particularly in Europe has led to the increased use of nitrogenous fertilizers which has also led to impacts on ecosystems. Increases in the numbers of grazing beef cattle sheep and goats changes in the socioeconomics of pastoral systems and the exploitation of new grazing areas have led to reductions in plant and animal biodiversity in many parts of the world in the last century. These pressures on the environment will continue to increase as the demand for animal products is stimulated by increases in the wealth of developing countries. Regulation will continue to develop as an important tool in the control of livestock systems in watershed and ecosystem management. For this regulation to be effective there must be a greater understanding of the functioning of grazed ecosystems. AIR AND WATER QUALITY A major impact on air quality is the quantity of methane produced by ruminant livestock and wild herbivores 80 100 m tonnes per year and its contribution to .