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 greenhouse gas emissions and the effect that this may have on global warming and ecosystems. Wild herbivores have been estimated to produce 4 8% of this methane.[1] The amount produced is a function of the numbers of ruminant livestock, their size, level of productivity, and type of diet, with low-quality roughage diets producing proportionately more. Approaches to reducing methane production through changes in diet, manipulating the rumen flora, and the administration of chemicals or drugs are being advocated, but are unlikely to have application to those ruminant livestock that are extensively managed.[2] Local effects on air quality can occur through ammonia production from manure from housed pig, poultry, and ruminant livestock and from the release of ammonia from feces and urine in intensively managed grazing systems where high levels of nitrogenous fertilizer are applied. The impacts are on increasing the concentration of NOx gases in the atmosphere, which contributes to the acidification and nitrification of soils and water, and hence impacts the productivity of ecosystems. As a result of increases in such gases in the atmosphere, changes in the composition of plant communities has occurred, for example, in the Netherlands,[3] and a loss of fish species from waters through acidification has occurred in many countries of the northern hemisphere.[4] In the European Community, regulation is being put in place to reduce such impacts on ecosystems.

Water quality is mainly affected by the movement of nutrients from manure sites, through the application of manure to soils as a fertilizer and the application of mineral fertilizers to crops used for livestock into rivers and streams. There are also issues relating to additives to feeds and silage effluent. The impact can result in nutrient saturation in soils and eutrophication of water courses, leading to major changes in aquatic ecology. A number of approaches have been adopted to attempt to minimize these impacts on water quality, including the appropriate positioning of housing for livestock and the building of manure systems that minimize the risk of contamination, and the disposal of manure to land in ways that reduce the likelihood of nutrients reaching water courses.[5] Because there is a mixture of point-source (housing) and diffuse pollution (disposal to land), approaches are now being taken to manage the problem at the level of the watershed. Targets are set for concentrations of pollutants in water; these are monitored and, by joint action, adhered to through a combination of best practice guidelines and regulation. An example is the Water Framework Directive of the Europe Commission.

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