Biodiversity is defined as "the variability among living organisms from all sources including, inter alia, 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." In simple terms, it can be described as the "diversity of life on Earth." 'Biodiversity' can be used as a synonym for living nature, with an emphasis on its complexity, at genetic, species and ecosystem levels. This complexity is vital in the maintenance of healthy ecosystem functioning, and it is important to recognize this when developing policies to protect the natural environment.

The direct drivers of biodiversity loss and degradation of ecosystem are habitat change, climate change, invasive alien species, overexploitation, and pollution. These elements are influenced by a series of indirect drivers of change, including governance, institutions and legal frameworks, science and technology.

According to UN Environment Programme, although much debate on biodiversity focuses on 'species', it is important to note that this is not a standard unit. The way species are defined differs between groups and between taxonomists. However, despite these ambiguities, measures of species richness and distribution are important tools in assessing the state of the environment and the direction and speed of change. The number of described species is now around 1.7 million. The estimated total number of species in existence ranges in order of magnitude from around 10 million to 100 million.

The greatest threats to biodiversity are the unsustainable harvesting of natural resources, including plants, animals and marine species, and the loss, degradation or fragmentation of ecosystems through land conversion for agriculture, forest clearing etc., pollution, and climate change.

The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is widely recognized as the most comprehensive, objective global approach for evaluating the conservation status of plant and animal species. The IUCN guides conservation activities of governments, NGOs and scientific institutions. The introduction in 1994 of a scientifically rigorous approach to determine risks of extinction that is applicable to all species, has become a world standard. The IUCN draws on and mobilizes a network of scientists and partner organizations working in almost every country in the world, who collectively hold what is likely the most complete scientific knowledge base on the biology and conservation status of species.

Direct threats to species are the proximate human activities or processes that have impacted, are impacting, or may impact the status of the taxon being assessed (e.g., unsustainable fishing or logging). Direct threats are synonymous with sources of stress and proximate pressures. Threats can be past (historical, unlikely to return or historical, likely to return), ongoing, and/or likely to occur in the future.
GEF benefits index for biodiversity (0 = no biodiversity potential to 100 = maximum)
GEF benefits index for biodiversity is a composite index of relative biodiversity potential for each country based on the species represented in each country, their threat status, and the diversity of habitat types in each country. The index has been normalized so that values run from 0 (no biodiversity potential) to 100 (maximum biodiversity potential).
The Global Environment Facility's (GEF) benefits index for biodiversity is a comprehensive indicator of national biodiversity status and is used to guide its biodiversity priorities. 

For each country the biodiversity indicator incorporates the best available and comparable information in four relevant dimensions: represented species, threatened species, represented ecoregions, and threatened ecoregions. To combine these dimensions into one measure, the indicator uses dimensional weights that reflect the consensus of conservation scientists at the GEF, and International Union for Conservation of Nature (IUCN), WWF International, and other nongovernmental organizations.

Reporting the proportion of threatened species on the Red List is complicated by the fact that not all species groups have been fully evaluated, and also by the fact that some species have so little information available that they can only be assessed as Data Deficient (DD). For many of the incompletely evaluated groups, assessment efforts have focused on species that are likely to be threatened; therefore any percentage of threatened species reported for these groups would be heavily biased (i.e., the percentage of threatened species would likely be an overestimate).

The index has been normalized so that values run from 0 (no biodiversity potential) to 100 (maximum biodiversity potential).