Diversity and Species Extinctions

Abstract

Species extinction leads to diversity in terms of number of species worldwide. Locally, however, immigration of species may at the same time in many areas increase the number of species, that is, the diversity. These contrasting processes of extinction and immigration have been accelerated by people over the millennia. This chapter discusses the causes and consequences of the processes over time, including examples from many habitats which demonstrate that trying to understand the causes and values of diversity in an ecosystem without analysis of its history can lead to erroneous conclusions. Several types of habitats where disturbance, often caused by people, increases and maintains diversity are analyzed from an historical perspective. Examples are also given of studies of past extinctions and their causation using models which lead to reinterpretation of the causes of the extinctions. Whether considering the early Holocene extinction of the megafauna of most continents the diversity of coppice woodlands in England, or the loss of thylacines and Tasmanian devils in Australia, this chapter illustrates that the relationship between cause and effect is almost always a complex, multifactorial one, and includes both human and non-human causation.