Environmental impacts of beef: soil degradation and loss
Impacts that take centuries to reverseWhile pasture itself may not result in annual soil erosion rates as high as from crop production, the initial conversion to pasture can lead to extreme erosion with loss of topsoil and organic matter that could take decades or centuries to replace.
In 1994, for example, soil loss in Brazil's Alto Taquari watershed was estimated at 70.39 metric tons per hectare per year, which is a high erosion rate. The degree of erosion increases proportionally to the increase in deforestation in the basin.
From 1977 to 1991, a 50% increase in habitat conversion was recorded. This has led to extensive degradation of the flooded valley-bottom vegetation. Pasture establishment results in the exposure of soil to the elements for several months, often during the rainy season.
Damage from overgrazing
Overgrazing damages soil structure and causes erosion. In many parts of the world, larger herds of cattle are being kept on ever smaller amounts of land, for longer periods of time. Overgrazing is a particular problem on slopes, where soils are more easily eroded and some grasses are crushed by the animals' hooves.
This is the case in many parts of the world where hillsides covered with cattle show the contoured signs of erosion and soil displacement. Overgrazing also thins and eventually removes ground cover so that the impact of wind and rain erosion increases.
Another cause of soil degradation and erosion from cattle is their repeated trampling over the same areas. The result is compaction or "soil pugging" due to the impact of cattle hooves. Soil compaction can destroy soil structure and results in resistance to root penetration, reduced water infiltration, and reduced aeration. All of these impacts harm beneficial soil microorganisms.
Compaction is considered to be inevitable with cattle production. However, the severity varies with the soil type, and is worst on wet soil that has a high clay content. Severe compaction provides a site for surface runoff that can result in serious erosion and even the creation of deep trenches, a process called gullying.
Degradation of surface watersAn additional environmental problem resulting form soil erosion is the degradation of surface waters. For example, some 80% of the cleared areas of the Brazilian Amazon and the cerrado (the savanna and forest-covered tableland that lies between the coastal forest zone and the Amazon) has been converted to pasture. Creation of these pastures has resulted in the increased siltation of streams and rivers.