4.16—Biodiversity and endemism

Biodiversity is the variety of life at three linked levels: genetic diversity within species, species diversity within communities, and ecosystem or habitat diversity across a region. Endemic species occur naturally in only one area.

Greater variety can give ecosystems resilience because different genes, species and habitats provide alternative responses to disturbance. Low diversity can make a population or ecosystem more vulnerable to one pathogen or environmental change.

A coral reef may contain many habitats and niches, while an isolated island species may have high uniqueness but a small range and high extinction risk. “More species” alone does not describe all biodiversity.

Species richness counts species; species diversity also considers abundance. Genetic diversity is variation in alleles, not simply the number of visible body forms.