Biodiversity: Species, Genes, and Ecology

The threats posed by human activity to biological diversity go to the heart of our environmental dilemma, and yet we know little about the true breadth or depth of the problem. The extinction of species is part of the evolutionary cycle of life, but the current cycle of extinctions is mainly human-made. Threats to biodiversity come mainly from habitat destruction, invasive species, pollution, population growth, and overexploitation. Habitat destruction poses particular threats to tropical forests, migratory species, and coral reefs. Climate change has become the latest and most troubling threat to biodiversity, posing systemic problems that can be resolved only through coordinated international action. There are numerous international conventions and programmes with biodiversity as their focus, but whether this amounts to an identifiable biodiversity regime is debatable. This chapter focuses on what human actions have meant for other living things, a notion encapsulated in the term biodiversity. Related to the more general term wildlife, and coined in 1986 for a conference on the topic (Harper and Hawksworth, 1994), it is both a synonym for and a contraction of the term biological diversity, and is concerned with the variety and the population of species, and their place in the natural system. Hall (2010a) defines biodiversity as ‘the total sum of biotic variation, ranging from the genetic level, through the species level and on to the ecosystem level’, while biological diversity is defined in the 1992 Convention on Biological Diversity as ‘the variability among living organisms from all sources including … terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.’