The importance of private land for biodiversity conservation is highlighted by rapid, broad‐scale sampling using citizen science

Abstract With the majority of terrestrial land privately owned and the Earth in a biodiversity extinction crisis, it is vital to improve our understanding of biodiversity on private lands. However, documenting biodiversity on private lands is challenging due to the time and financial constraints in gaining access, hindering our understanding of the value of private lands for conservation. In recent decades, citizen science has offered a unique opportunity to obtain biodiversity data on private lands through engaging landholders and encouraging participation in biodiversity documentation. To determine the value of citizen science for biodiversity sampling on private lands and enhance our understanding of the importance of private lands, we leveraged nearly 500,000 frog occurrence records from across New South Wales, Australia, from the Australian citizen science project, FrogID. Pairing this data with land tenure data, we found that private land was relatively better sampled than public land by citizen science data, with 86% of records from private lands. Private and public lands supported moderately different biodiversity, and frog species richness was predicted to likely be higher on private land once aridity and sampling density were accounted for. Citizen science offers a novel technique to supplement biodiversity data collection by rapidly amassing occurrence data on broad scales. Private lands are essential for global biodiversity conservation, encompassing the majority of land and providing vital habitat for both threatened and non‐threatened taxa.