Biodiversity: an overview

Abstract

Biodiversity is the very basis of human survival and economic well-being, and encompasses all life forms, ecosystems and ecological processes. The current estimates of the total number of species on earth vary from 5 to more than 100 million, with a more conservative figure of 13.6 million species. Of these, only 1.78 million species have yet been described and awarded scientific names. Thus, our knowledge of diversity is remarkably incomplete. Biodiversity at any point in time is the balance between the rates of speciation and extinction. Biodiversity is not uniformly distributed on the earth and shows prominent latitudinal and altitudinal gradients. At least five major mass extinctions have occurred in the past at geologic-time boundaries. Studies indicate that we have entered into the sixth phase of mass extinctions. In all ecosystem types, terrestrial, freshwater and marine, species populations are declining. The current rates of species extinction are 100–1000 times higher than the background rate of 10⁻⁷ species/species year inferred from fossil record. It is now in the order of 1,000 species per decade per million species. Today we seem to be losing two to five species per hour from tropical forests alone. This amounts to a loss of 16 m populations/year or 1,800 populations/h. Major drivers for changes of biodiversity in future, in decreasing rank of their impact are land use change, climate change, N deposition, biotic exchange and atmospheric loading of CO₂. Accuracy of estimates of the total number of resident species and current rates of extinction remains undetermined, and the impact of species deletions on ecosystem function and stability is still a subject of debate among ecologists. There are two basic, often complementary strategies for biodiversity conservation. The in situ strategy emphasizes the protection of ecosystems for the conservation of overall diversity of genes, populations, species, communities and the ecological processes which are crucial for ecosystem services. Establishment of networks of protected areas are effective in this regard as these have the possibility to conserve primary forests and red-listed ecosystems. The concept of biodiversity banking could induce public participation. Establishment of the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services, an independent, international science panel (like IPCC) would help coordinate and highlight research on pressing topics, conduct periodic assessments on regional as well as global scales and provide predictions.