Abstract
Protected areas (PAs) remain the cornerstone of global faunal conservation strategy, yet their effectiveness varies
substantially with management quality, size, connectivity, and surrounding landscape context. This study evaluates the
conservation effectiveness of 48 protected areas spanning five IUCN management categories (I-VI) across Sweden,
France, and the Netherlands using standardised multi-taxon biodiversity surveys (birds, mammals, herpetofauna, and
ground beetles; n = 24,817 individual records across 384 taxa), PA governance quality scores, and paired outside-PA
reference site comparisons. Species richness inside PAs exceeded paired outside-PA reference sites by a mean of 38.4
+- 6.8% across all four taxonomic groups (paired t-test t(47) = 8.92, p < 0.001). PA effectiveness -- measured as the
inside-outside biodiversity ratio -- was significantly predicted by management effectiveness score (METT; beta = 0.48 +-
0.08, p < 0.001), PA area (beta = 0.31 +- 0.07, p < 0.001), and connectivity index (beta = 0.24 +- 0.07, p = 0.001). IUCN
Category I/II strict reserves showed the highest mean inside-outside biodiversity ratio (1.74 +- 0.18), while Category V/VI
protected landscapes showed the lowest (1.18 +- 0.12), but Category V/VI sites supported significantly higher functional
diversity of farmland-adapted taxa than strict reserves. Thirty-one percent of PAs scored below the METT threshold
associated with measurable biodiversity benefit (score < 50/100), constituting 'paper parks' with biodiversity levels
indistinguishable from outside. Connectivity to other PAs was the strongest predictor of mammal occupancy within PAs
(beta = 0.54 +- 0.09), underscoring the importance of ecological networks over isolated reserve expansion. These results
support evidence-based target-setting under the Kunming-Montreal Global Biodiversity Framework 30x30 goal.