The global push for solar energy could come with a hidden biodiversity cost, a study of more than 2,300 Chinese counties reports. According to the findings, stronger policies promoting solar development were associated with a decline in bird diversity, largely because ecologically diverse croplands and grasslands were converted to developed land. The expansion of renewable energy can help combat climate change, but large-scale solar development may create a new environmental trade-off by converting or fragmenting habitat and contributing to biodiversity loss. Because birds are relatively well monitored across large areas and respond sensitively to changes in vegetation, breeding habitat, and food availability, shifts in their diversity can reveal ecological impacts that conventional measures may overlook. In China, where rapidly growing solar capacity is expected to become a major component of the energy system, photovoltaic installations already cover thousands of square kilometers; they may increasingly affect bird populations and their habitats. Moreover, China’s solar power infrastructure has been strongly shaped by government policies, which have largely determined its location and scale.

Here, Huiming Zhang and colleagues investigated the ecological consequences of solar expansion. Zhang et al. assembled a large dataset covering 2,344 counties across China from 2014 to 2023. Their dataset combined bird observations, solar-energy policies, environmental conditions, and socioeconomic information. This allowed the authors to assess the relationship between solar-promoting policies and local bird diversity. They also looked at impacts of changes in land use, vegetation, and agricultural productivity. The findings revealed that stronger policies promoting solar expansion were associated with significant declines in bird diversity – a one-standard-deviation increase in policy intensity corresponded to a 2.10% reduction in the bird biodiversity index. These effects were strongest in wealthier and non-desert regions and disproportionately affected geographically widespread species. This was largely due to rapid land conversion, particularly the transformation of cropland and grassland into developed areas, which reduced vegetation diversity. Zhang et al. also identified a paradoxical pattern they call “inferior greening,” in which landscapes appeared greener based on higher Leaf Area Index but became ecologically poorer overall. “The next step is to move from biodiversity measurement to valuation by linking changes in bird diversity to ecosystem services and conservation values,” writes Yuanning Liang in a related Perspective. “Without such valuation, policy analysis gives insufficient weight to conservation, and benefit-cost analysis can understate the social cost of development. Just as climate policy requires credible estimates of climate damages to inform the social cost of carbon, credible estimates of biodiversity values are needed when sustainable development policies alter ecosystems.”

For reporters interested in topics on research integrity, co-author Kai Wu notes; “In our field, scientific integrity increasingly depends on transparent data practices, reproducible analytical frameworks, and responsible integration of interdisciplinary methods. As research increasingly connects climate change mitigation and adaptation, modern energy systems, and ecological processes with socioeconomic systems, developing shared standards for data validation and model transparency will be essential to ensure that scientific evidence can reliably inform global sustainability policies.”

Dense evergreen forests in Canada’s snow-covered boreal regions can absorb enough sunlight to offset 6 to 20 percent of their reported carbon benefit, according to a new publication by the UN University. Researchers warn that Canada’s carbon accounting largely overlooks this warming effect, potentially overstating the climate value of reforestation and carbon credits. They call for a new Net Cooling Standard that accounts for surface reflectivity, wildfire risk and long-term carbon storage, while prioritizing mixed-species forests that deliver more durable climate cooling.