The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus, initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness.

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1. Documentation of carry-over effects (COEs), defined as effects resulting from events that occurred in a previous time period, has largely been observational and understanding of specific mechanisms underlying COEs is still lacking. To investigate this, we simulated an environmental perturbation during the spring migration of a long-lived bird species and looked at the subsequent effects on various breeding parameters.2. We captured female greater snow geese Anser caerulescens atlanticus on their spring staging sites and maintained individuals in captivity for up to 4 days before releasing them. We re-observed females 3000 km North, on their Arctic breeding grounds, to estimate their breeding propensity (i.e. probability of initiating a reproductive event for a given year), and measured their arrival date, laying date, clutch size and nesting success.3. Only proxies of breeding propensity were affected by our manipulation, which decreased as the time spent in captivity increased. However, females were able to overcome the effects of captivity in two out of the 3 years of experimentation with normal or good environmental conditions at the breeding site. 4. When facing the additional challenge of poor environmental conditions, many individuals manipulated during migration apparently curtailed their reproductive effort by skipping breeding. This experiment is the first to show that breeding propensity is an important parameter affected by COEs resulting from stressful events prior to reproduction in long-lived species.