ABSTRACT
All herbivores consume selected plants and plant parts from their environment. This selective defoliation through the removal of photosynthetic or reproductive tissues impedes the grazed plant’s ability to compete with other ungrazed plants in the community. Grazing animals are important agents of environmental change, acting to create spatial heterogeneity, accelerate successional processes, and control switching between alternative states. Chronic herbivory can change composition, structure, and production of plant communities (habitat). With a decline in habitat diversity a concomitant decline in species diversity can be expected; some species simply have no place to live. If populations of individual species fail to persist because of declining habitat diversity, then genetic diversity is reduced. However, one must consider that some changes in plant structure, composition, and production may in fact improve or have no effect on species diversity because new habitats are created. Some species may decline, but others will increase. Such variables as season of use, intensity of defoliation, frequency of defoliation, and forage selectivity separately and together impact the grazed plant community. Knowledge of these variables can be of use to managers designing grazing systems to minimize the impacts on biodiversity.
