Fowl and floating photovoltaic farms – is a joint existence possible?

Floating photovoltaic (FPV) farms are being presented as an idea for producing renewable energy without taking up valuable land. Researchers at Cornell University decided to investigate how their development could threaten birds in the northeastern U.S. states, a key region for avifauna migration.

Renewable energy and environmental costs

Float-mounted and anchored to the bottoms of bodies of water, FPV panels can, according to previous analyses, generate up to 25 percent of regionally used solar energy in the northeastern United States. At the same time, studies indicate that even a small coverage of water bodies (as little as 1 percent) can change the temperature and oxygenation of the water and affect the local microclimate. A systematic review of the literature has shown that most of the environmental changes resulting from FPV installations have a negative impact on aquatic ecosystems.

The authors of the study, the results of which were published in late December 2025 in the journal Environmental Science & Technology, set out to see what risks FPVs might pose to birds. The analysis covered 14 states lying within the Atlantic migration route. Based on hydrographic data and technical criteria (including a minimum area of about 2 hectares, distance from transmission lines <1.6 km and roads <0.8 km), 16,620 water bodies potentially suitable for FPV installations were selected.

The behaviors of 291 bird species were studied, whose occurrence within a 5 km radius of these reservoirs was determined using data from eBird, a scientific project of the Cornell Lab of Ornithology, It estimates the relative abundance of birds with high spatial (3 × 3 km) and temporal (weekly) resolution based on the reports collected. Both water and land birds are included in the study.

Vulnerability index – which species are most at risk?

Since there is a lack of direct data on bird collisions with FPV, the authors created a vulnerability index (VI) based on three equivalent components:

• Collision risk (dependent on flight maneuverability and visual acuity);
• degree of protective threat (based on population size and abundance trends);
• Habitat susceptibility (based on habitat preferences and requirements and dependence on open water).

The distribution of values was strongly skewed, with a median VI of 0.07, meaning that most species were rated as not very sensitive to the presence of floating photovoltaic farms. The highest possible level of sensitivity (VI = 1.00) was reached by the horned grebe(Podiceps auritus) and the black scoter(Melanitta americana). High index values in the range of 0.85 to 0.9 were also identified for the red-breasted darter(Calidris canutus), the long-winged darter( Calidris bairdii), the American merganser(Limosa haemastica) , and the sea darter(Calidris maritima).

These species had very high average risk scores measured on a scale of 1 to 5: flight maneuverability 4.3 (±0.2), visual acuity 4.7 (±0.2), protective concern index 4.9 (±0.1) and maximum habitat vulnerability (5). They are mainly water birds requiring an open surface for takeoff and landing.

Floating photovoltaic farms by geography – where is the risk greatest?

The highest risk of conflicts between birds and floating PV farms has been identified in the Finger Lakes region of New York State, along the Delaware River (Delaware-New Jersey border), in the Roanoke River basin in Virginia, and in known migration hotspots such as Cape May and Cape Cod.

Importantly, there was no significant statistical relationship between estimated energy production from FPV and the level of risk to birds. In other words, a high energy potential of a reservoir does not automatically mean a high risk to avifauna – and vice versa. This suggests that, in many cases, sites can be selected that provide good energy output with relatively low wildlife risk.

At the same time, the analysis showed that there were specific reservoirs where both indicators – energy production potential and risk to vulnerable species – reached high values. In such places, a decision-making dilemma arises: the choice of location can bring significant climatic benefits (high energy production), but at the same time increase pressure on species most vulnerable to collisions and habitat loss.

Biofouling and biodiversity – the hidden costs of floating PV plants

The analysis showed a very strong positive correlation between the occurrence of threats to birds and the risk of so-called biofouling, i.e. fecal soiling of panels. 103 species of waterbirds were evaluated, using the relationship between their body weight and defecation rate. In practice, this means that the most important reservoirs for sensitive species are at the same time the most vulnerable to a decline in plant performance. This risk was particularly high near large bodies of water – along the Atlantic coast and on the Great Lakes.

Reservoirs with a high risk of bird collisions with FPV were also more likely to have high social and recreational value. Avoiding such locations can therefore have a double benefit – for nature and local communities.

Interestingly, the reservoirs whose energy use was considered most risky to sensitive bird species were not those ranked as most valuable in terms of habitat and species diversity and potential to withstand environmental pressures. Avoiding the erection of FPV installations on reservoirs important to sensitive birds will not necessarily translate into the protection of areas of highest value for the resilience of entire freshwater ecosystems. Therefore, the authors emphasize that the existence of automatic benefits for various conservation goals should not be assumed – they must be analyzed and taken into account in the decision-making process each time.

Small tanks – big impact

About 80 percent of the highest-risk reservoirs are dammed reservoirs or small ponds. This is important, because it is precisely such bodies of water that are most often used today for floating photovoltaic farms and are often covered to a higher degree with panels. At the same time, they act as migration stops and habitat connectors.

The authors emphasize that while some species – especially waterbirds: plovers and gulls – may be particularly vulnerable, there is generally ample room to minimize conflicts through appropriate site selection. The strong coincidence of the occurrence of threats to birds and the risk of biofouling provides an additional economic argument for avoiding the most sensitive water bodies.

The results of the study allow for the first such broad spatial mapping of the risk of interactions between birds and floating photovoltaic farms in the region, and propose an analytical framework that can be applied beyond. Implementing FPV installations on water surfaces in a careful, monitored manner and with an adaptive approach can combine climate goals with biodiversity conservation, provided that siting decisions are based on ecological relationships and not solely on energy potential.

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Source:

Potential Interactions Between Birds And Floating Photovoltaic Solar Energy: Spatially Informed Species Vulnerabilities, Techno-Ecological Risks, And Sustainability Trade-Offs, Allison D. Binley, Adam Gallaher, Amanda D. Rodewald, and Steven M. Grodsky, Environmental Science & Technology 2026 60 (1), 510-521, DOI: 10.1021/acs.est.5c09819