The Impact of Browsing and Grazing Herbivores on Biodiversity

Abstract

Biodiversity definable as the variety of life in all its forms. Biodiversity encompasses the entire biological hierarchy. Two different hierarchical schemes are frequently used to classify biological entities (Sarkar and Margules 2002): a spatial hierarchy and a taxonomic hierarchy. The spatial hierarchy runs from biological molecules and macromolecules, through cell organelles, cells, individuals, populations and meta-populations, communities, ecosystems ultimately to the biosphere; and the taxonomic hierarchy from alleles through loci, linkage groups, genotypes, subspecies, species, genera, families, orders, classes, phyla, and kingdoms. Each level is highly heterogeneous and, even more important, most entities are poorly defined. For example, there is still much confusion about the species concept, to mention one of the key entities in biology (Sarkar and Margules 2002). Furthermore biodiversity also comprises the relationships between entities within a hierarchy. Through all the confusion of the concept of biodiversity it is very difficult to operationalise and, therefore, various proximates have been developed which allow the estimation of (subsets of) biodiversity in the field. According to Ricotta (2005): ‘biodiversity may be defined simply as a set of multivariate summary statistics for quantifying different characteristics of community structure’.