Comparative Diversity Indices Across Protected Areas

Abstract

Protected areas -- the primary tool for in situ biodiversity conservation globally -- vary enormously in their biodiversity value, management effectiveness, and representativeness of regional species pools, yet systematic comparative assessment of protected area biodiversity using standardised diversity indices across multiple taxonomic groups and protected area categories is rarely conducted at the regional scale required for strategic conservation planning. This study computed and compared eight widely used diversity indices (Shannon H', Simpson D, Margalef d, Chao1 richness estimator, Faith's PD, functional richness FRic, functional dispersion FDis, and the Berger-Parker dominance index) across 42 protected areas in the Baltic States (Estonia, Latvia, Lithuania) spanning four IUCN management categories (I-II: strict reserves n=10; III: natural monuments n=8; IV: habitat/species management n=12; V-VI: landscape/resource reserves n=12) and four taxonomic groups (vascular plants, birds, beetles, and bats; 2,840 species-site records; 2019-2022). Diversity indices showed category-specific patterns: strict reserves (IUCN I-II) showed the highest phylogenetic and functional diversity (Faith's PD = 284 +/- 48 Ma; FRic = 0.724 +/- 0.084) but not the highest species richness -- with habitat/species management areas (IUCN IV) showing the highest mean species richness per site (Shannon H' = 3.84 +/- 0.48) through active management maintaining diverse structural habitats. Index congruence analysis (Kendall's W) showed high concordance between taxonomic richness indices (W = 0.874) but low concordance between taxonomic and functional/phylogenetic indices (W = 0.424-0.584), confirming that species richness alone is an inadequate surrogate for functional and phylogenetic diversity across protected areas. A Protected Area Biodiversity Integration Index (PABII) combining all eight indices weighted by their independent information content (from PCA) predicted protected area management effectiveness ratings (METT scores) with r = +0.84 and provided a more complete biodiversity summary than any single index.