The reported decline in bird diversity tracks birdwatching effort, not birds

Chenchen Ding , Yang Liu, Zhengwang Zhang, Zhiheng Wang

A recent analysis in Science links a photovoltaic policy-stringency index to citizen-science bird records aggregated to county-months and concludes that China’s solar-expansion policy reduced Shannon diversity by 2.10% per standard deviation of stringency. Reproducing that estimate exactly from the replication package and checking its inputs against record-level data from the same platform, we show that the outcome variable measures the observation process rather than bird communities: nearly half of the checklists carry no abundance information, corrupted counts enter the regression unfiltered, and birdwatching effort grew 171-fold while concentrating in accessible, economically developed counties, in step with policy stringency. Once total effort is modeled, the coefficient reverses sign and is null in all 18 effort-adjusted specifications; the preferred estimate,