A large number of small forests typically harbor higher biodiversity than a small number of large forests totaling the same area, suggesting that small patches are disproportionately valuable for biodiversity conservation. However, policies often favor protection of large forest patches. Here we demonstrate a global trend of higher deforestation in small than large forest patches: the likelihood that a randomly selected forest plot disappeared between 1992 and 2020 increased with decreasing size of the forest patch containing that plot. Our results imply a disproportionate impact of forest loss on biodiversity relative to the total forest area removed. Achieving recent commitments of the post‐2020 Global Biodiversity Framework will require revision of current policies and increased societal awareness of the importance of small habitat patches for biodiversity protection.