Nest-box provisioning as an offset or greenwashing practice in renewables projects

The global expansion of renewable energy, particularly photovoltaic plants (PV), aims to meet rising energy demands while lowering carbon emissions and addressing climate change. In Spain, these projects threaten biodiversity, especially in steppe environments. Spanish law encourages energy companies to implement biodiversity offsets, such as nest-box installation, which is a vastly applied measure (in up to 85.6 % of photovoltaic plants). This study critically examines the ecological suitability of nest-box installation in PV developments and assesses its effectiveness in biodiversity conservation. Through a comprehensive review of Environmental Impact Assessments (EIAs) for PV plants across Spain, the most biodiverse country and one where more renewables projects are planned in the EU, we identify recurring flaws in their design and implementation, including the inappropriate application of nest-boxes in areas where target species do not reside, poor nest-box placement, and lack of post-installation monitoring. Furthermore, the use of nest-boxes often bypasses the IUCN mitigation hierarchy, contributing to misleading perceptions of environmental responsibility—known as greenwashing—while failing to address the true ecological consequences of PV infrastructure. We argue that a more scientifically rigorous approach is needed, including compliance with the mitigation hierarchy, fitness assessments for species using nest-boxes, and regulation of their installation. A national coordination and advisory center should be established to standardize practices, ensure effective monitoring, and provide scientific oversight of nest-box use in PV projects. This will help optimize biodiversity conservation efforts and reduce the risk of ecological harm.