WHAT THE EVIDENCE SAYS
Researchers synthesized population trends from 129 studies spanning 4,748 sites. Formerly common species declined more strongly than rare species in terrestrial and marine assemblages; freshwater assemblages showed no clear directional pattern. Rare species present at the start also declined, while colonizing species partly compensated within the rarest abundance class.
WHY IT MATTERS / OUR READ
Stable local species richness can coexist with substantial community reorganization and loss of numerically dominant species. Because common species often carry a large share of biomass and ecosystem function, conservation dashboards that emphasize richness alone can miss meaningful functional erosion.
CAVEATS / UNCERTAINTY
The synthesis pools heterogeneous monitoring programs, taxa and time series. Abundance rank is relative within assemblages, and the study does not imply that rare species are secure; many rare species also declined.
SOURCE
Nature Communications · Original evidence
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