More than 25% of world’s land surface is grazed by domestic animals, which represents a surface area more than twice of that used for cultivation and almost the same area occupied by forests or other land uses. Mismanagement of livestock grazing, mainly in form of unbalanced animal numbers, is considered by many authors the most important cause of land degradation, outstripping even deforestation, industrialization or soil tillage. Nonetheless, the effects of overgrazing/undergrazing are not equally severe in all environments, with overgrazing being much more intense in areas where water is a limiting factor.
In Mediterranean land-systems such as dehesas in Spain or montados in Portugal and dry grasslands of Greece and Italy, overgrazing leads to sheet erosion and soil compaction as well as to the lack of plant regeneration, among other degradation processes. In the United States, for example, many studies have demonstrated that overgrazing can provoke a decrease in pasture production and fodder quality. Australian rangelands have also been affected by overgrazing in different climatic areas throughout the country. However, there are many other grazing systems that are scarcely known worldwide such as Brazilian faxinal where open fields of short shrubs grazed mainly by cattle are the dominant landscape. On the other hand, undergrazing and land abandonment rise major concerns for proper land management in many areas of the globe.
Contributions dealing with the occurrence of land degradation processes such as soil erosion and compaction, the importance of landform elements, the hydrologic impact of grazing and the effects on pasture yield and fodder quality in grazing areas worldwide as well as those focused on finding optimum animal stocking rates under different scenarios are welcome.