Executive Vice President, World Wildlife Fund, Washington, D.C.
Before dwelling on the economic, social, and political problems that are fundamental to present problems and future prospects, there are two aspects of natural science that require attention but have not yet been mentioned in this volume: the abundance of relatively few of the many species on Earth and the limitations deriving from our shallow knowledge of diversity.
One of the great questions of biological science arises when biological diversity is viewed through ecological glasses: Why are ecosystems generally made up of a large number of species of which only a few are abundant? While the roster of rarer species in an ecosystem is much longer in tropical regions than at higher latitudes, there is a general tendency to accumulate large numbers of species in all but the most simple ecosystems.
This pattern can be generally portrayed by graphing the relative abundance (for example, the percentage of total individuals or of total biomass) of species against the order of species from most to least abundant (Figures 47–1 and 47–2). In early successional communities, there is a smaller number of species and the most abundant ones constitute a larger fraction of the community, i.e., are more dominant.