Environmental Impact of Meat Production - Water Resources

Water Resources

Virtual water use for livestock production includes water used in producing feed. However, virtual water use data, such as those shown in the table, are often unrelated to environmental impacts of water use. For example, in a high-rainfall area, if similar soil infiltration capacity is maintained across different land uses, mm of groundwater recharge and hence sustainability of water use tends to be about the same for food crop production, meat-yielding livestock production, and saddle horse production, although virtual water use per kg of food produced may be several hundred L, several thousand L, and an infinite number of L, respectively. In contrast, in some low-rainfall areas, some livestock production is more sustainable than food crop production, from a water use standpoint, despite higher virtual water use per kg of food produced. This is because unirrigated land in many water-short areas may support grassland ecosystems in perpetuity, and thus may be able to support well-managed, extensive production of grazing cattle or sheep with a sustainable level of water use, even where large-scale production of more water-demanding food crops would be unsustainable in the long run due to inadequate surface water supplies and inadequate groundwater recharge to sustain a high level of withdrawn water use for irrigation. Such considerations are important on much rangeland in western North America and elsewhere that can support cow-calf operations, backgrounding of stocker cattle, and sheep flocks. In the US, withdrawn surface water and groundwater use for crop irrigation exceeds that for livestock by about a ratio of 60:1.

Also, the high virtual water use figures associated with meat production do not necessarily imply reduction of water use if food crops are produced, instead of livestock. For example, some grazing lands are unsuitable for food crop production, so that evapotranspirational water use would continue on land vacated by livestock, while additional water would be needed for crops to provide substituting food from lands elsewhere, and additional water would also be needed to produce substitutes for the non-food products of livestock. (In the US, Land Capability Classes V, VI and VII contain soils unsuited for cultivation, much of which is suitable for grazing. Of non-federal land in the US, about 43 percent is classed as unsuitable for cultivation.)

Irrigation accounts for about 37 percent of US withdrawn water use, and groundwater provides about 42 percent of US irrigation water. Groundwater depletion is a concern in some areas because of sustainability issues (and in some cases, land subsidence and/or saltwater intrusion). A particularly important North American example where depletion is occurring involves the High Plains (Ogallala) Aquifer, which underlies about 174,000 square miles in parts of eight states, and supplies 30 percent of the groundwater withdrawn for irrigation in the US. Some irrigated livestock feed production is not hydrologically sustainable in the long run because of aquifer depletion. However, rainfed agriculture, which cannot deplete its water source, produces much of the livestock feed in North America. Corn (maize) is of particular interest, accounting for about 91.8 percent of the grain fed to US livestock and poultry in 2010. About 14 percent of US corn-for grain land is irrigated, accounting for about 17 percent of US corn-for-grain production, and about 13 percent of US irrigation water use. About 40 percent of US corn grain is fed to US livestock and poultry. Together, these figures indicate that most production of grain used for US livestock and poultry feed does not deplete water resources and that irrigated production of grain for livestock feed accounts for a small fraction of US irrigation water use. However, where production relies on irrigation from groundwater reserves, water table monitoring is appropriate to provide timely warning if groundwater depletion occurs.