In Europe, and particularly in the Mediterranean Basin, the abandonment of traditional land-use practices has been reported as one of the main causes of decline for open-habitat species. Data from large-scale bird and butterfly monitoring schemes in the north-east Iberian Peninsula were used to evaluate the impact that land abandonment has had on local biodiversity. Species’ habitat preferences, along a gradient from open to forest habitats, were significantly related to population trends: for both birds and butterflies, open-habitat species showed the most marked declines while forest species increased moderately. Multi-species indicators for tracking the impact of land abandonment on bird and butterfly populations were developed using habitat preference estimates and population trend indices. The patterns shown by these indicators were in line with the changes occurring in forest cover in the monitoring sites. This study reveals that multi-species indicators based on monitoring data from different taxonomic groups (here, birds and butterflies) may usefully be employed to track impacts of environmental change on biodiversity.