Biodiversity & ecosystems
Gamma Diversity
Definition
Gamma diversity is the total species diversity across all communities within a larger region — the pooled or regional species richness. In Whittaker's 1960 framework it complements alpha diversity (diversity within a local site) and beta diversity (turnover between sites), with multiplicative beta expressed as the ratio of gamma to mean alpha richness.
References
framework and definitions
alpha–beta–gamma relationships
Overview
What it means
A region's gamma diversity reflects both how rich its typical sites are and how much those sites differ from one another. Two regions can share the same gamma diversity with very different structures — a few rich sites or many distinctive ones — which is why conservation planning considers the three scales together.
How it is used
Ecologists partition diversity into alpha, beta, and gamma components to compare regions, assess habitat fragmentation effects, and set priorities for protected-area networks; gamma diversity is the currency of regional-scale biodiversity targets.
Why it matters
It connects plot-level ecology to landscape and biogeographic questions, and clarifies whether diversity loss stems from local degradation or homogenisation across sites.