Long-term biodiversity monitoring data from two hydroelectric dam projects in northeast Portugal, 2006–2023

This Data Descriptor provides a harmonised biodiversity data compilation derived from 149 datasets collected between 2006 and 2023 during environmental impact assessment and ecological monitoring of two hydroelectric developments in Portugal. The input datasets were collected under standardised field protocols and curated jointly by private consultants, academic institutions and two successive dam operators (EDP and Movhera). Datasets were standardised to Darwin Core and published on the Global Biodiversity Information Facility (GBIF). Their validated records were harmonised across datasets into a single compilation accessible as a citable GBIF occurrence download. Overall, the compiled dataset contains 1,989,401 biodiversity records, including occurrence and abundance data for nearly 3,800 taxa from terrestrial and aquatic ecosystems spanning six biological kingdoms. Here we detail the spatial, temporal and taxonomic coverage of the compilation, the workflow used for data harmonisation and quality control, and the structure of the published files. The dataset supports research on hydropower impacts, long-term biodiversity trends and conservation planning, and illustrates a practical model for transparent biodiversity data sharing by the private sector.