Environmental impacts of animal agriculture
The environmental impacts of animal agriculture vary because of the wide variety of agricultural practices employed around the world. Despite this, all agricultural practices have been found to have a variety of effects on the environment to some extent. Animal agriculture, in particular meat production, can cause pollution, greenhouse gas emissions, biodiversity loss, disease, and significant consumption of land, food, and water. Meat is obtained through a variety of methods, including organic farming, free-range farming, intensive livestock production, and subsistence agriculture. The livestock sector also includes wool, egg and dairy production, the livestock used for tillage, and fish farming.
Animal agriculture is a significant contributor to greenhouse gas emissions. Cows, sheep, and other ruminants digest their food by enteric fermentation, and their burps are the main source of methane emissions from land use, land-use change, and forestry. Together with methane and nitrous oxide from manure, this makes livestock the main source of greenhouse gas emissions from agriculture.[1] A significant reduction in meat consumption is essential to mitigate climate change, especially as the human population increases by a projected 2.3 billion by the middle of the century.[2][3]
Resource use[edit]
Food production efficiency[edit]
About 85% of the world's soybean crop is processed into meal and vegetable oil, and virtually all of that meal is used in animal feed.[11] Approximately 6% of soybeans are used directly as human food, mostly in Asia.[11]
For every 100 kilograms of food made for humans from crops, 37 kilograms byproducts unsuitable for direct human consumption are generated. [12] Many countries then repurpose these human-inedible crop byproducts as livestock feed for cattle.[13] Raising animals for human consumption accounts for approximately 40% of total agricultural output in industrialized nations.[14] Moreover, the efficiency of meat production varies depending on the specific production system, as well as the type of feed. It may require anywhere from 0.9 and 7.9 kilograms of grain to produce 1 kilogram of beef, between 0.1 to 4.3 kilograms of grain to produce 1 kilogram of pork, and 0 to 3.5 kilograms of grains to produce 1 kilogram of chicken.[15][16]
Effects on ecosystems[edit]
Soils[edit]
Grazing can have positive or negative effects on rangeland health, depending on management quality,[99] and grazing can have different effects on different soils[100] and different plant communities.[101] Grazing can sometimes reduce, and other times increase, biodiversity of grassland ecosystems.[102][103] In beef production, cattle ranching helps preserve and improve the natural environment by maintaining habitats that are well suited for grazing animals.[104] Lightly grazed grasslands also tend to have higher biodiversity than overgrazed or non-grazed grasslands.[105]
Overgrazing can decrease soil quality by constantly depleting it of necessary nutrients.[106] By the end of 2002, the US Bureau of Land Management (BLM) found that 16% of the evaluated 7,437 grazing allotments had failed to meet rangeland health standards because of their excessive grazing use.[107] Overgrazing appears to cause soil erosion in many dry regions of the world.[14] However, on US farmland, soil erosion is much less on land used for livestock grazing than on land used for crop production. According to the US Natural Resources Conservation Service, on 95.1% of US pastureland, sheet and rill erosion are within the estimated soil loss tolerance, and on 99.4% of US pastureland, wind erosion is within the estimated soil loss tolerance.[108]