Biodiversity

Biodiversity is the variability of life on Earth, encompassing genetic diversity within species, the diversity of species across ecosystems, and the structural complexity of ecosystems themselves. Scientists measure it through species richness, the count of species in an area, species evenness, how uniformly individuals are distributed among those species, and diversity indices such as the Shannon and Simpson indices that combine both measures. Current estimates suggest roughly 8.7 million terrestrial species and 2.2 million oceanic species exist, though most remain undocumented. Biodiversity underpins ecosystem services that sustain human welfare, including provisioning of food, water and materials, regulating functions such as climate control and pest management, and cultural benefits such as recreation. Roughly half of pharmaceutical compounds derive from biological sources, and about 80 percent of the global population relies on natural medicines. The economic value of the resources biodiversity provides has been estimated at around 150 trillion dollars a year, about twice global GDP, and its ongoing loss threatens all of these systems.