Tropical insect biodiversity loss from forest-pasture conversion is substantially underestimated across spatial scales

Understanding how biodiversity responds to forest conversion across spatial scales is essential for designing effective conservation and monitoring strategies. Using abundance-based models at a spatial resolution of 2 × 2 km, we analyzed 243 dung beetle species sampled across 865 sites within 13 Colombian ecoregions and found that biodiversity loss is substantially amplified at broader spatial scales under simulated scenarios. Biodiversity loss, measured as the proportion of species negatively affected by conversion, increased by 25% at a near-national scale compared with local-scale assessments, while the abundance ratio of the median-sensitivity species declined by 42%, revealing pronounced erosion that remains hidden at local scales. Estimates based on a single ecoregion underestimated biodiversity loss by a factor of 1.65, with at least five to six ecoregions required for estimates to converge toward near-national patterns. These results show that reliance on limited spatial coverage can obscure the magnitude of biodiversity erosion in heterogeneous tropical systems, pointing to the need for broad, regionally representative sampling to generate reliable biodiversity indicators and inform conservation decision-making. Local management decisions must therefore be interpreted within a regional context, as sites showing weak or no local declines may still contribute substantially to broader-scale biodiversity loss.