The terms ‘biological diversity’ or ‘biodiversity’ are of relatively recent usage in international law. Until the 1980s, international instruments tended to address ‘wildlife’ or ‘wild fauna and flora’, and focused on species and habitats. ‘Biodiversity’ is a more inclusive term and can be considered in relation to three hierarchical categories which describe different aspects of living systems measured in different ways: genetic diversity; species diversity; and ecosystem diversity.
However measured, there is a scientific consensus that biodiversity is being lost. The 2015 Global Forest Resources Assessment indicated that 129 million hectares of forest have been lost since 1990, although the net rate of global deforestation slowed in that period. The 2010 third Global Biodiversity Assessment (GBO 3) recorded that more than 95 per cent of North American grasslands have been lost, and that savannah and grassland have suffered severe declines elsewhere. The GBO 3 also noted that terrestrial habitats have become highly fragmented, threatening the viability of many species and ecosystem services. The Millennium Ecosystem Assessment reported that about 20 per cent of the world's coral reefs have been destroyed and another 20 per cent degraded. In relation to species populations, the GBO 3 suggested that the population of wild vertebrate species fell by an average of 31 per cent globally between 1970 and 2006, with particularly severe declines in the tropics and in freshwater ecosystems. Much remains unknown about biodiversity – only a fraction of the species thought to exist have been described, and, as the Millennium Ecosystem Assessment acknowledged, ‘the extent of extinctions of undescribed taxa is unknown, the status of many described species is poorly known, it is difficult to document the final disappearance of very rare species, and there are time lags between the impact of a threatening process and the resulting extinction’.
Reasons for conserving nature and biodiversity are essentially threefold. First, biodiversity provides an actual and potential source of biological resources including, for example, for use as food and feed, as well as for pharmaceutical, industrial and other applications. Second, biodiversity contributes to the maintenance of the biosphere in a condition that supports human and other life. This concept of ‘ecosystem services’ provided by biodiversity has become central to contemporary policy debates on the issue. Third, biodiversity conservation may be based on ethical, intrinsic, aesthetic and cultural considerations.