How is biodiversity best defined?

Biodiversity is best defined as the variety of life in a particular habitat or ecosystem. This definition encompasses not only the different species present but also the genetic diversity within those species, and the variety of ecosystems themselves. Biodiversity is crucial for the resilience of ecosystems, supporting processes such as productivity, nutrient cycling, and providing ecosystem services like pollination and clean water.

The total number of individuals in an ecosystem gives a measure of abundance but does not account for the variety of species or genetic diversity. The distribution of species across geographical areas speaks more to biogeography than biodiversity itself. Evolutionary adaptations of organisms over time are related to biodiversity but do not capture the current state or variety of life existing within ecosystems at a given time. Thus, defining biodiversity with a focus on the variety of life in a specific habitat or ecosystem captures the essential elements that contribute to biological richness and ecological health.