Grazing and Browsing:
Balance between Grasses, Shrubs and Trees

Description: many pastoral areas and grasslands are made up of a lower layer of grasses and others plants and an upper layer of woody plants, palms or bamboo. In order to maintain grazing activities and to keep the vegetation and landscape open, a balance has to be found between the grasses and the shrubs and trees.

In general, the bulk of the forage is produced by the lower layer. Shrubs and trees also provide a small quantity of additional forage. This is particularly important in dry regions, but excessive cover can eliminate the grasses because of competition for light and water. When forests expand and encroach on areas with different types of vegetation, including grasslands, plant and animal diversity is modified. When woody plants become the dominant species, there is generally a deterioration in pasture quality, natural vegetation and biodiversity.

This situation is common in tropical and temperate regions in subhumid or humid climates where there are climax forests. On the other hand, in dry environments, a certain number of trees or shrubs is considered beneficial for both livestock and the environment.

Grazing and browsing changes the competitiveness of and the balance between the lower and upper vegetative layers, i.e. between plants, shrubs and trees.

In wet climates, grazing is often beneficial to trees to the point where they become dominant. However, in dry climates, herbivores damage young plants and seedlings which limits the extension of shrubs. Excessive grazing reduces the capacity of grasses to compete with taller plants. In savannah areas, livestock help prevent bush fires or reduce their effect on trees by eating undergrowth that could be a fire risk (cf. effects on combustible material).

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