Solar farms reduce bird diversity, a Chinese study published last week in the international, peer-reviewed journal Science, announced. But the country’s scientific community has contested the reliability of its birdwatching data and the significance of its statistical findings.

The study, published Aug. 21, was led by researchers at Nanjing University of Information Science and Technology, in collaboration with other researchers from China, Vietnam, and the United States. 

Examining 2,344 Chinese counties from 2014 to 2023, it found that cutting carbon emissions may come at the cost of protecting biodiversity, as birds’ cropland and grassland habitats are converted for solar projects.

China has been expanding solar power to meet its targets of peaking carbon emissions by 2030 and reaching carbon neutrality by 2060. By 2024, solar facilities covered an estimated 4,520 square kilometers of land and are projected to make up nearly 45% of the country’s electricity generation by 2060.

“The research is not against solar expansion but rather offers policy recommendations on how to do it better,” Li Shanjun, one of the study’s corresponding authors and a professor at the Stanford Doerr School of Sustainability, told Sixth Tone.

The authors suggested developing solar projects in areas where solar panels cause lower ecological impact, such as in deserts; promoting phased rollouts rather than sudden large-scale expansion; and assessing ecological recovery beyond vegetation density, as they found uniform vegetation inferior for housing bird habitats.

However, experts from the China Ornithological Society said “flaws” in the study’s bird observation data could undermine its conclusions, according to a Tuesday article published on the society’s official WeChat account. The academic group includes ornithologists from universities, research institutes, and conservation organizations nationwide.

The crowdsourced dataset from the China Birdwatching Record Center contained missing bird counts, erroneous records, and reporting differences driven by the growing popularity of birdwatching, the Society wrote.

Among the issues, over 40% of the over 500,000 reports collected during the nine years recorded the presence of species, indicated using the number “1.” However, the Society noted that this is commonly used as a placeholder when the observer did not enter a count, rather than that only one bird was seen, making the data unreliable.

The analysis also said the data had not been properly cleaned. One record from 2015, for example, reported over 2 billion little egrets at a single location. The record was retained in the dataset, contributing to bird totals “beyond a reasonable range.” 

Meanwhile, the original study may have removed some migratory waterbirds’ records at wintering sites as statistical outliers, as they recorded tens of thousands of birds at a given location, “potentially underestimating true bird diversity,” the analysis said.

The analysis also noted that birdwatching records surged between 2021 and 2023 amid a growing birdwatching boom in the country, just as authorities were introducing significant solar policies. This, it argued, makes it difficult to determine whether changes in biodiversity data were driven by increased birdwatching or photovoltaic development.

Chinese ecologists generally agree that amid cutting carbon emissions, biodiversity can be protected through careful planning, Ma Zhijun, deputy director of the China Ornithological Society and a co-author of the analysis, told Sixth Tone. Ma is also a professor at Fudan University’s School of Life Sciences.

Such planning means avoiding key wildlife habitats when building solar, wind, and other renewable energy facilities, Ma said. 

He added that the “easy availability” of birdwatching datasets has led researchers without a background in bird ecology to use them without “fully understanding their limitations.” 

“This paper is a typical example of the problem,” he said. The analysis recommended cross-checking data from different sources and cleaning datasets before using them to assess large-scale changes.

A separate statistical analysis of the study’s data also found that birdwatching duration — where longer sessions correlate with more species detected — had a significantly greater effect on measured bird diversity than solar policy.

That analysis, published Sunday, was conducted by Lai Jiangshan, an ecology professor at Nanjing Forestry University, and Zhang Shuang, an associate researcher at the Chinese Academy of Sciences.

“This (comparison of birdwatching duration and solar policy) was not reflected in the Science paper, meaning its conclusion is not statistically supported,” Zhang told Sixth Tone. 

Li, one of the Science paper’s corresponding authors, responded that the two measures were “not comparable” and that the comparison was not informative for policymaking.

“Policy variables typically account for only a small share of variation in environmental outcomes,” he said. “But policies remain among the few tools people can actively change.”

Li also rejected any suggestion that the team had concealed metrics, noting that the full data and code used to run the statistical models were publicly available. Regarding the birdwatching data, he said the findings were tested using different statistical methods, and outliers were removed.

Editor: Marianne Gunnarsson.

(Header image: Solar panels cover the mountains in Anshun, Guizhou province, Aug. 4, 2024.)