Global impact of the COVID-19 lockdown on biodiversity data collection.

The COVID-19 pandemic triggered different governmental responses across borders, with cascading effects on people's movements and on biodiversity data collection. We quantified changes in the number of species occurrence records collected during the first global lockdown (March 15th to May 1st 2020) relative to pre-pandemic levels using data from the Global Biodiversity Information Facility (GBIF). We modelled how such changes relate to the stringency of governmental policy responses, changes in human mobility, and countries' population size and economic class across 129 countries. We further focused on data from the community science project eBird, which constitutes the largest dataset in GBIF, to investigate changes in participation and activity patterns of individual observers (eBirders) during the lockdown. We found that the decreases in GBIF records correlated with declines in numbers of visitors to parks and outdoor areas, and were significantly larger in developing countries compared to developed ones. While the activity ranges of eBirders shrunk across all countries analysed, the number of eBirders in developing and least developed countries declined more than in developed countries, as the lockdown disrupted the influx of international visitors. Our results suggest that community-based, local monitoring programmes are essential to reduce biases in global biodiversity monitoring.