Mountain areas of Italy experienced substantial socio-ecological changes over the last four decades. Partly due to outmigration, traditional agro-forestry activities and cultural landscapes were progressively abandoned and forest expanded substantially. Biodiversity trends observed during the last 30 years of rewilding are unlikely to continue under climate change. Understanding the decadal impacts of rewilding remains challenging. Biodiversity monitoring data are scant, scarcely integrated and scattered. Some vegetation plot time-series do exist, but they are essentially point observations in space. Achieving a complete picture of biodiversity change requires integrating different data, expertise, and mostly, viewpoints. Integrating biodiversity surveys with data that is available with complete spatial coverage, such as remote sensing, is a necessary first step. But interpreting biodiversity changes also requires considering people’s perceptions and knowledge. Only a qualitative-quantitative approach allows us to understand not only the patterns and trends of biodiversity change, but also the reasons why it changed. This study proposes an interdisciplinary, data-driven approach to understand historical and future trends of plant biodiversity in Italian rewilded mountain areas. We produced spatially explicit assessments of vegetation change between 1990 and 2020 in three mountain protected areas spanning the Italian Peninsula: 1) Eastern Alps (Lagorai mountain range); 2) Northern Apennines (Foreste Casentinesi Monte Falterona e Campigna NP), and 3) Central Apennines (Velino Massif). To do so, we used generalized dissimilarity modelling (GDMs) to model the dissimilarity of plant assemblages as a function of their geographical distances, ecological dissimilarities, and differences in land cover derived by remote sensing. After calibrating the GDMs with historical and newly collected vegetation plot data, the maps of predicted species composition at different times were created, whose comparison allowed highlighting areas where change in land cover induced the largest changes in species composition, and quantified the consequences for regional plant diversity.