Livestock are often accused of contributing to soil erosion in different ways. One classic example is the deforestation in the Amazon to produce grazing land, which has attracted much attention from ecologists and the mass media. Yet clearly it is not the animals that cut down the trees! The responsibility lies with the business people who - aided and abetted by government subsidies - cause irreversible damage by destroying the forests to plant pastures for short-term financial gain. Another example is that of the long-term overgrazing of semi-arid rangelands, which has lead increasingly to desertification. It is well known, however, that sound resource management could avoid this deterioration of the environment while maintaining a productive system.
If livestock are managed in an appropriate way, they can even contribute to the reduction of soil erosion. The use of perennial fodder trees and high biomass fodders (sugar cane) and the establishment of fodder hedgerows on the contour provide excellent protection against erosion and should be established practices.
Agro-sylvo-pastoral systems in semi-arid areas are a viable proposition for the protection of the fragile soils of these regions. Multipurpose trees contribute to the protection of the soil, as well as to animal and energy production, and store carbon that would otherwise contribute to atmospheric carbon dioxide.
It is also a criticism of ruminant production that the animals contribute to the greenhouse effect, since they produce methane as an end-product of rumen digestion. It should be recognized, however, that ruminant populations have increased only moderately compared with those of other species, and that their contribution is estimated at just 2.5 percent of the total greenhouse gases (Leng, 1993). Gas emissions from cars and industry are far greater and have increased at a much higher rate. There are two ways to reduce methane emission from livestock: by introducing an appropriate diet supplementation that could reduce ruminant methane production per unit of milk or meat by a factor of 4 to 6, and by favouring the production of meat from monogastric animals.
The third complaint about livestock is pollution resulting from accumulated excrete and nitrite-contaminated groundwater. This is primarily a problem with intensive, industrialized production systems. It can be reduced by implementing manure processing technologies as well as nutrition and feeding strategies that reduce the amount of nitrogen and phosphorus in the diet of animals. It could also be controlled by limiting the size of such enterprises to that which allows excrete to be easily accommodated on neighbouring lands or used for fertilizer products. Smallholders usually cause less pollution than large intensive units.