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Portugal — Local bird richness rose as rural land use retreated, but open-land specialists did not share the gains

A 20-year resurvey found a 28% rise in local bird richness driven mainly by forest species and generalists.

Evidence
Peer-reviewed
Geography
Côa River basin, Portugal
System
Mediterranean upland mosaics

WHAT THE EVIDENCE SAYS

Resurveys of 213 four-square-kilometre cells found mean local richness rising from about 21 to 27 species between the early 2000s and 2023–2024. Forest-associated and generalist birds drove most gains while farmland specialists showed little net improvement or slight declines.

WHY IT MATTERS / OUR READ

Land abandonment and passive woody recovery can produce genuine local biodiversity gains while simultaneously shifting community composition away from species tied to long-maintained open agro-pastoral habitats.

CAVEATS / UNCERTAINTY

Historical transect locations were not known precisely and observer teams differed between periods. Regional richness stayed similar; the major change was redistribution and local occupancy, not a large gain in the total regional species pool.

SOURCE

Oecologia · Original evidence
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