Fig. 1

Open in situ forest data are critical for the monitoring and mitigation of deforestation, forest degradation, biodiversity loss, and climate change (a), but sampling density of in situ forest data across the world, in number of sample plots per 1000 square kilometers, is generally low (b). Sampling density was calculated at the ecoregion²⁵ level, based a global database compiled by the Global Forest Biodiversity Initiative (GFBI, https://www.gfbinitiative.org/). Containing approx. 1.3 million sample plots, GFBI is one of the largest in situ forest datasets.