Cattle - Environmental Impact

Environmental Impact

See also: Environmental effects of meat production

A report from the Food and Agriculture Organization (FAO) states that the livestock sector is "responsible for 18% of greenhouse gas emissions". The report concludes, unless changes are made, the damage thought to be linked to livestock may more than double by 2050, as demand for meat increases. Another concern is manure, which if not well-managed, can lead to adverse environmental consequences. However, manure also is a valuable source of nutrients and organic matter when used as a fertilizer. Manure was used as a fertilizer on about 15.8 million acres of US cropland in 2006, with manure from cattle accounting for nearly 70% of manure applications to soybeans and about 80% or more of manure applications to corn, wheat, barley, oats and sorghum. Further, substitution of manure for synthetic fertilizers in crop production can be environmentally significant, as between 43 and 88 MJ of fossil fuel energy are used per kg of nitrogen in manufacture of synthetic nitrogenous fertilizers.

One of the cited changes suggested to reduce greenhouse gas emissions is intensification of the livestock industry, since intensification leads to less land for a given level of production. This assertion is supported by studies of the US beef production system, suggesting practices prevailing in 2007 involved 8.6% less fossil fuel use, 16.3% less greenhouse gas emissions, 12.1% less water use, and 33.0% less land use, per unit mass of beef produced, than those used in 1977. However, these numbers included not only feedlots, but also feed production, forage-based cow-calf operations, backgrounding before cattle enter a feedlot, and animals culled from the dairy industry.

The number of American cattle kept in confined feedlot conditions fluctuates. From January 1, 2002 through January 1, 2012, there was no significant overall upward or downward trend in the number of US cattle on feed for slaughter, which averaged about 14.046 million head over that period. Previously, the number had increased; it was 12.453 million in 1985. Cattle on feed (for slaughter) numbered about 14.121 million on January 1, 2012, i.e. about 15.5% of the estimated inventory of 90.8 million US cattle (including calves) on that date. Of the 14.121 million, US cattle on feed (for slaughter) in operations with 1000 head or more were estimated to number 11.9 million. Cattle feedlots in this size category correspond to the regulatory definition of "large" concentrated animal feeding operations (CAFOs) for cattle other than mature dairy cows or veal calves. Significant numbers of dairy, as well as beef cattle, are confined in CAFOs. CAFOs are defined as "new and existing operations which stable or confine and feed or maintain for a total of 45 days or more in any 12-month period more than the number of animals specified" where "rops, vegetation, forage growth, or post-harvest residues are not sustained in the normal growing season over any portion of the lot or facility." They may be designated as small, medium and large. Such designation of cattle CAFOs is according to cattle type (mature dairy cows, veal calves or other) and cattle numbers, but medium CAFOs are so designated only if they meet certain discharge criteria, and small CAFOs are designated only on a case-by-case basis.

A CAFO that discharges pollutants is required to obtain a permit, which requires a plan to manage nutrient runoff, manure, chemicals, contaminants, and other wastewater pursuant to the Clean Water Act. The regulations involving CAFO permitting have been extensively litigated. Commonly, CAFO wastewater and manure nutrients are applied to land at agronomic rates for use by forages or crops, and it is often assumed that various constituents of wastewater and manure, e.g. organic contaminants and pathogens, will be retained, inactivated or degraded on the land with application at such rates; however, additional evidence is needed to test reliability of such assumptions . Concerns raised by opponents of CAFOs have included risks of contaminated water due to feedlot runoff, soil erosion, human and animal exposure to toxic chemicals, development of antibiotic resistant bacteria and an increase in E. coli contamination. While research suggests some of these impacts can be mitigated by developing wastewater treatment systems and planting cover crops in larger setback zones, the Union of Concerned Scientists released a report in 2008 concluding that CAFOs are generally unsustainable and externalize costs.

An estimated 935,000 cattle operations were operating in the USA in 2010. In 2001, the US Environmental Protection Agency (EPA) tallied 5,990 cattle CAFOs then regulated, consisting of beef (2,200), dairy (3,150), heifer (620) and veal operations (20). Since that time, the EPA has established CAFOs as an enforcement priority. EPA enforcement highlights for fiscal year 2010 indicated enforcement actions against 12 cattle CAFOs for violations that included failures to obtain a permit, failures to meet the terms of a permit, and discharges of contaminated water.

Grazing by cattle at low intensities can create a favourable environment for native herbs and forbs; in many world regions, though, cattle are reducing biodiversity due to overgrazing. A survey of refuge managers on 123 National Wildlife Refuges in the US tallied 86 species of wildlife considered positively affected and 82 considered negatively affected by refuge cattle grazing or haying. Proper management of pastures, notably managed intensive rotational grazing and grazing at low intensities can lead to less use of fossil fuel energy, increased recapture of carbon dioxide, fewer ammonia emissions into the atmosphere, reduced soil erosion, better air quality, and less water pollution.

Some microbes in the cattle gut carry out anaerobic process known as methanogenesis, which produces methane. Cattle and other livestock emit about 80 to 93 Tg of methane per year, accounting for an estimated 37% of anthropogenic methane emissions, and additional methane is produced by anaerobic fermentation of manure in manure lagoons and other manure storage structures. The 100-year global warming potential of methane, including effects on ozone and stratospheric water vapor, is 25 times as great as that of carbon dioxide. Methane's effect on global warming is correlated with changes in atmospheric methane content, not with emissions. The net change in atmospheric methane content was recently about 1 Tg per year, and in some recent years there has been no increase in atmospheric methane content. Mitigation options for reducing methane emission from ruminant enteric fermentation include genetic selection, immunization, rumen defaunation, diet modification and grazing management, among others. While cattle fed forage actually produce more methane than grain-fed cattle, the increase may be offset by the increased carbon recapture of pastures, which recapture three times the CO₂ of cropland used for grain.