A few related points
Our estimates show that the number of those suffering from chronic hunger in the world has topped one billion in 2009 – one billion and 20 million to be more precise. The challenge that lies ahead is to secure the food security of these one billion hungry people and also to double food production in order to feed a population projected to reach 9.2 billion by 2050.
There is increasing pressure on ecosystems and natural resources – land, water and biodiversity. The livestock sector is only one of many sectors and human activities contributing to the pressure. In some cases its impact on ecosystems is out of proportion with the economic signiﬁcance of the sector. Livestock contribute less than 2 percent of global gross domestic product (GDP) but produce 18 percent of global greenhouse gas (GHG) emissions
Increased trade ﬂows, along with the growing concentration of animals, often in proximity to large human populations, have contributed to increased risks of spreading of animal diseases and to a rise in animal-related human health risks globally.
In many parts of the world, the transformation of the livestock sector is occurring in the absence of strong governance, resulting in market failures related to natural-resource use and public health. Nor has growth in the sector been adequately managed to deal with the increasing pressures on natural resources or to provide control and management of animal disease
Growth in consumption of livestock products per capita has markedly outpaced growth in consumption of other major food commodity groups (Figure 1). Since the early 1960s, consumption of milk per capita in the developing countries has almost doubled, meat consumption more than tripled and egg consumption increased by a factor of ﬁve.
Livestock is the world's largest user of land resources, with grazing land and cropland dedicated to the production of feed representing almost 80 percent of all agricultural land. The sector uses 3.4 billion hectares for grazing (Table 12) and 0.5 billion hectares for feed crops (Steinfeld et al., 2006); the latter figure corresponds to one-third of total cropland.The total land area occupied by pasture is equivalent to 26 percent of the ice-free terrestrial surface of the planet. Much of this area is too dry or too cold for cropping, and is only sparsely inhabited.
Ranching-induced deforestation is a common feature in Central and South America (Wassenaar et al., 2006). At the same time, grasslands are increasingly fragmented and encroached upon by cropland and urban areas. White, Murray and Rohweder (2000) estimate that more than 90 percent of the North American tallgrass prairie and almost 80 percent of the South America cerrado have been converted to cropland and urban uses.
The Millennium Ecosystem Assessment estimated that 10–20 percent of all grassland is degraded, mainly by overgrazing. Pasture degradation is generally a consequence of a mismatch between livestock density and the capacity of the pasture to recover from grazing and trampling. Among the environmental consequences of pasture degradation are soil erosion, degradation of vegetation, release of carbon from organic matter deposits, reduction in biodiversity and impaired water cycles.
According to the Millennium Ecosystem Assessment (MEA, 2005), the most important direct drivers of biodiversity loss and ecosystem service changes are: habitat change (such as land-use changes, physical modification of rivers or water withdrawal from them, loss of coral reefs, and damage to sea floors resulting from trawling); climate change; invasive alien species; overexploitation; and pollution.
Livestock contribute directly or indirectly to all these drivers of biodiversity loss, from the local to global levels.
Livestock-related land use and landuse change modify ecosystems that are the habitats for given species. Livestock contribute to climate change (see "Livestock and climate change", below), which in turn has an impact on ecosystems and species. The sector also directly affects biodiversity through transfer of invasive alien species and overexploitation, for example through overgrazing of pasture plants. Water pollution and ammonia emissions, mainly from industrial livestock production, reduce biodiversity, often drastically in the case of aquatic ecosystems. Pollution from livestock enterprises, as well as overfishing to provide fishmeal for animal feed, reduces biodiversity in marine ecosystems (Reid et al., 2009).
Feed production causes emissions in the agriculture, forestry (through land-use change), transport and energy categories. Enteric fermentation and manure management associated with livestock rearing lead to methane and nitrous oxide emissions accounted for under agriculture. Slaughtering, processing and distribution cause emissions accounted for in the industry, energy and transport categories. Along the animal food chain, the major sources and amounts of emissions are:
Land use and land-use change: 2.5 gigatonnes of CO2 equivalent. Includes CO2 release from forest and other natural vegetation replaced by pasture and feed crop in the neotropics and carbon releases from soils, such as pasture and arable land dedicated to feed production.
Feed production (excluding carbon released from soil and plants): 0.4 gigatonnes of CO2 equivalent. Includes CO2 from fossil fuel used in manufacturing chemical fertilizer for feed crops and N2O and ammonia (NH3) released by chemical fertilizers applied to feed crops and from leguminous feed crops.
Animal production: 1.9 gigatonnes of CO2 equivalent. Includes CH4 from enteric fermentation and CO2 from on-farm use of fossil fuel.
Manure management: 2.2 gigatonnes of CO2 equivalent. Includes CH4, N2O