© T. Eglin et al., Published by EDP Sciences 2025

1 Introduction

The deployment of floating Photovoltaïc (FPV) is accelerating worldwide. The first FPV plants were installed in 2007 and, by 2016, cumulative installed capacity reached nearly 1 GW globally (Rodríguez-Gallegos et al., 2024). By 2023, FPV capacity reached 7.7 GW, with ∼90% of the capacity operating in Asia. The Netherlands and France are the largest markets in Europe (Selj et al., 2025), with respectively ∼4% and ∼1% of the global capacity set up in 2022 (Rodríguez-Gallegos et al., 2024).

In the meantime, the deployment targets for ground-mounted solar PV are significant. In France, the installation of 1,8–2,7 GW per year is expected between 2023 and 2028 (Ministère de la Transition Ecologique et Solidaire, 2018). It is equivalent to ∼3 500–∼5 200 ha.year⁻¹, assuming 1.93 MW.ha⁻¹ (Blaydes et al., 2025). This puts pressure on land availability. Like agrivoltaics, FPV could partially address the need for land. Within the national support mechanisms for industrial projects, waterbodies are empirically considered as low risk sites for land-use conflicts, similar to old quarries and polluted sites (Commission de Régulation de l'Energie, 2025). There is thus an urgent and crucial need to better understand the potential impacts of the development of FPV on these ecosystems.

A research workshop entitled “Floating Photovoltaics (FPV) and Biodiversity: What Effects on Lake Ecosystems?” was held on June 19, 2025, at the Institute of Fluid Mechanics of Toulouse in France, with the support of the European Life Program “Biodiv'France”. Organized by the Research Center on Biodiversity and Environment (CRBE), the Occitanie Region, the French Biodiversity Office (OFB) and the French Agency for Ecological Transition (ADEME), the event brought together scientists, public authorities, NGOs, and industry stakeholders (i) to share the ecological implications of FPV on lake ecosystems and (ii) to discuss on FPV eco-design and to identify future perspectives for research.

To meet these objectives, the workshop was structured around three problematics. The first one was focused on the assessment of FPV deployment potential and on how to integrate biodiversity conservation issues. This topic was discussed around a case-study conducted by the French Occitanie Region (AREC Occitanie, 2021). Second, research perspectives on the ecological impacts of FPV plants on waterbodies ecosystems were discussed based on a recent literature review (e.g., Nobre et al., 2023; Nobre et al., 2025c) and on ongoing projects and their associated research questions. Third, the possibility to develop eco-designed FPV was discussed, based on a review of the potential sources of pressure exerted by floating photovoltaic (FPV) systems on lake ecosystems, as well as the associated risks of impact on their physical, chemical and biological components. The workshop then explored possible mitigation strategies through the lens of eco-voltaic principles developed for ground-mounted solar PV (Tölgyesi et al., 2023).

This workshop was part of a national initiative to reconcile the deployment of renewable energy and biodiversity conservation, in line with the 2030 French Biodiversity Strategy and the development of the French Renewable Energies and Biodiversity Observatory (https://observatoire-energies-renouvelables.biodiversité.gouv.fr/) officially established by the French law No. 2023-175 of March 10-2023, on accelerating the production of renewable energies. Overseen by the Ministries responsible for Energy and Ecology, this Observatory was implemented in 2024 by the French Office for Biodiversity (OFB) and the French Agency for Environment and Energy Management (ADEME). It aims to inform public and private decision-making by providing clear and objective knowledge on the impacts of renewable energies on biodiversity, soils, and landscapes, as well as on the effectiveness of proposed mitigation measures. The work of the Renewable Energies and Biodiversity Observatory is based on the review of scientific knowledge, evaluation and harmonization of monitoring protocols and technical guidelines for stakeholders (Tab. 1). It is co-funded by the European Union under the LIFE program BIODIV'FRANCE (https://www.ofb.gouv.fr/le-projet-life-biodivfrance#::text=Le%20projet%20LIFE%20BIODIV'FRANCE%20a%20pour%20finalit%C3%A9%20d'accompagner,de%2050%2C45%20M%E2%82%AC).

2 Assessment of FPV deployment potential and integration of biodiversity conservation issues

According to Rodríguez-Gallegos et al. (2024), FPV capacity could reach up 22 TW globally, if installed on 10% of the area of 249 717 inland natural and artificial water bodies documented in the SERIS (Solar Energy Research Institute of Singapour) database, which is a combination of the Global Reservoir Dam Database v1.1 (GRanD − https://www.globaldamwatch.org/grand), the Global Lakes and Wetlands Database (GLWD − https://www.worldwildlife.org/pages/global-lakes-and-wetlands-database) and FAO's AQUASTAT database on dams (https://www.fao.org/aquastat/en/databases/dams/). In France, AREC Occitanie's regional government has identified a significant potential for FPV deployment in the Occitanie Region, owing to its favorable geography and high solar irradiance. Over 520 water bodies larger than 10 hectares were identified as potentially and technically usable for FPV deployment. After applying environmental exclusion criteria − such as UNESCO sites and waterbodies included in the Natura 2000 protected areas network (European Environment Agency, 2023), and assuming a coverage rate of 30% and a conversion ratio of 1 MW per hectare, the regional FPV potential was estimated at ∼1 GW.

Regarding the potential impacts on biodiversity Nobre et al. (2024) showed that FPV systems are currently predominantly installed on small artificial water bodies—such as ponds, gravel pits, and reservoirs—with high average coverage rates (mean 34%, up to ∼90% in some cases). The study also showed that FPV coverage tends to be higher on water bodies with regular morphologies, where installation is technically easier and more cost-effective. These small water bodies were found to be particularly vulnerable to ecological disruption due to their limited buffering capacity and high area-to-volume ratios. This previous study has highlighted the importance of improving and sharing knowledge on small waterbodies sensitivities to FPV, pleading for a better integration of biodiversity issues early in the development and the conception of FPV plant (e.g., coverage rates, floating system).

3 Research perspectives on the ecological impacts of FPV systems on waterbodies

The ecological impacts of FPV plants remain poorly quantified by robust empirical studies despite their rapid expansion across the globe. According to (Nobre et al. 2023, 2025c), FPV installations can potentially (i) reduce light penetration, wind mixing-effect, and water temperature, thereby altering primary production and energy transfer within lake food webs, (ii) modify thermal stratification and oxygenation of the water column, with cascading effects on the waterbody metabolism, (iii) create artificial habitats that may benefit or disrupt native species, potentially altering community composition, trophic interactions, and greenhouse gas balances (e.g., Ilgen et al., 2025- https://doi.org/10.1051/kmae/2025008; Vouhe et al., 2025 − https://doi.org/10.1051/kmae/2025005). Recent studies are beginning to demonstrate the existence of physical effects (e.g., Nobre et al., 2025a) and to identify impacts on biological compartments (e.g., Nobre et al., 2025b). Notably, the impacts should vary with lake size and morphology, FPV design, and environmental conditions in the lake ecosystems (e.g., productivity, nutrient level). However, robust experimental studies on these effects are still lacking. Moreover, a significant part of the published literature has inadequate experimental design, potentially producing misleading results: lack of control, limited number of replicates, configuration not representative of a commercial-scale installation (e.g., pilot PFV plant). Based on existing knowledge, several research directions were identified (Tab. 2).

4 Eco-design of FPV: toward a shared reference framework

Main ecological pressures and potential impacts caused by FPV projects include (i) construction-phase disturbances (e.g., anchoring, traffic, land clearing, sediment resuspension), (ii) operating phase disturbances (e.g., coverage by panels, cables, anchors, fencing), (iii) alteration of air-water exchanges, temperature and light regimes, (iv) modification of physical, chemical and biological properties (e.g., primary production) of the lake ecosystem and (v) habitat modification and potential suitability for invasive species. The concept of eco-voltaic proposes a structured approach to minimize the ecological footprint of ground-mounted solar PV systems (Tölgyesi et al., 2023). Application of this concept to FPV was discussed with 20 stakeholders from diverse backgrounds, grouped by professions: FPV industrials, environmental consulting firms, French state representatives, Angling Association and NGOs. A draft of an FPV eco-design technical guide, expected to be published in 2027, was reviewed. This guide proposes a step-by-step framework covering i) the site selection and the project sizing based on the ecological sensitivity of the lake (e.g., coverage ratio), ii) the platform design (e.g., layout, site plan, anchoring), iii) the ecosystem design (e.g., identification of ecological functions or ecosystem services to be preserved/restored, riparian restoration), and iv) the management of the park (e.g., maintenance, monitoring, adaptive management) (Tab. 3). Importantly, all participants supported the development of a shared and evolving reference document that facilitates dialogue among stakeholder groups. All participants also emphasized that recommendations should be based on scientific evidence and supported by real-world examples.

5 Conclusion

The workshop offered a unique opportunity to provide a comprehensive overview of the current knowledge and challenges for FPV systems and their ecological impacts on lake ecosystems. FPV deployments are accelerating worldwide, notably on small waterbodies that are vulnerable to environmental perturbations. The prospects of deployment are significant. Hence, biodiversity considerations should be better included in potential assessment, and early in the sitting and conception of FPV plants. FPV plants may influence multiple environmental parameters in the water column − light, temperature, dissolved oxygen, wind fetch, gas exchange with the atmosphere, primary producers, carbon cycling, … − with effects varying significantly across lake types and environmental conditions. The effects on some of these physical parameters have already been demonstrated on some biological communities, but there is a need for pursuing the study of biological consequences of these physical shifts at the ecosystem level, on the habitats (e.g., rest, breeding and feeding areas for birds and bats) and in the long-term. To do so, experimental design is determinant: standardized BACI design must be privileged. Data from regulatory environmental monitoring could also be used, but monitoring methods need to be harmonized. However, these previous guidelines would not replace research projects with dedicated experimental designs. Future research projects should promote interdisciplinary collaborations (i.e., ecological, technical, and social sciences) to have more integrated assessment at the ecosystem level, and to develop FPV eco-design. Potential contamination (e.g., microplastic, degradation products, heavy metals) and ecotoxicological risks assessment should also be carefully assessed.

Acknowledgements

We thank Julien Cucherousset, Régina Nobre and Sophie Bernard for their feedback and contributions in improving the draft of this paper. We are also grateful to all those who participate to the workshop. Finally, we would like to thank the journal editors and the two anonymous reviewers.

References

All Tables