Samenvatting
Habitat loss is the single most important driver of global animal biodiversity decline, yet the dose-response relationship
between habitat area reduction and species richness loss varies substantially across taxa, landscape contexts, and
spatial scales. This study quantifies the impact of habitat loss on animal diversity across four taxonomic groups -- ground
beetles (Carabidae), breeding birds, amphibians, and small mammals -- in agricultural landscapes spanning a 10-92%
natural habitat loss gradient in Germany, Sweden, and Denmark (n = 72 study sites, 2020-2023; n = 18,641 individual
records across 312 taxa). Species-area relationships (SARs) were modelled for each taxon using the power function (S =
cA^z); z-values ranged from 0.18 (small mammals) to 0.41 (amphibians), with amphibians and birds showing the
steepest diversity-area declines. Threshold analysis identified non-linear diversity collapses at 68-74% habitat loss for
birds and amphibians, consistent with habitat amount thresholds documented in global meta-analyses. Functional
diversity (functional richness, evenness, and divergence) declined more steeply than taxonomic diversity across the
habitat loss gradient for all four groups (mean Hedges' g = -0.84 vs. -0.61 for taxonomic), indicating disproportionate loss
of functionally unique species. Landscape connectivity (measured as the proportion of natural habitat within 2 km radius)significantly moderated the habitat loss-diversity relationship for mobile taxa (birds: interaction term beta = 0.31, p =0.004), but not for amphibians (p = 0.18), underscoring the dispersal barrier created by intensively managed agricultural matrices for low-mobility species. These findings quantify evidence-based habitat retention thresholds applicable to landscape planning under the EU Nature Restoration Law targets.