Floral resource diversity supports pollination function and is increasingly threatened by global environmental change. Using long-term data on native insect-pollinated plants across 200 landscapes in southern Sweden, we assessed changes in taxonomic and functional diversity over 26 years in relation to land cover heterogeneity. Species richness declined significantly, while the three functional diversity measures (functional richness, functional evenness, and functional dispersion) remained stable, suggesting that declines are not particularly associated with certain floral trait combinations. This suggests some degree of functional resilience in floral trait composition despite ongoing species loss. However, spatial and temporal variation was substantial, with some landscapes experiencing increases in floral diversity, while others showing a decrease. Landscapes with greater land cover heterogeneity supported higher levels of floral resource diversity, but this diversity was found to decline over time, potentially due to reduced management of semi-natural grasslands and transfer to conifer plantations. Initial diversity did not buffer against losses but rather indicated higher potential for decline. Our findings highlight the complex interactions between landscape heterogeneity, biodiversity loss, and ecosystem function. Conserving structurally heterogeneous landscapes and maintaining diverse floral traits are critical to supporting pollinator communities under global change. Our study underscores the need for landscape-scale strategies to preserve pollination services and ecosystem resilience as the human pressures on biodiversity intensify.