jats:pProtected areas (<jats:styled-content style="fixed-case">PA</jats:styled-content>s) are a key tool in efforts to safeguard biodiversity against increasing anthropogenic threats. As signatories to the 2011–2020 Strategic Plan for Biodiversity, 196 nations pledged support for expansion in the extent of the global <jats:styled-content style="fixed-case">PA</jats:styled-content> estate and the quality of <jats:styled-content style="fixed-case">PA</jats:styled-content> management. While this has resulted in substantial increases in <jats:styled-content style="fixed-case">PA</jats:styled-content> designations, many sites lack the resources needed to guarantee effective biodiversity conservation. Using management reports from 2167 <jats:styled-content style="fixed-case">PA</jats:styled-content>s (with an area representing 23% of the global terrestrial <jats:styled-content style="fixed-case">PA</jats:styled-content> estate), we demonstrate that less than a quarter of these <jats:styled-content style="fixed-case">PA</jats:styled-content>s report having adequate resources in terms of staffing and budget. Using data on the geographic ranges of the 11,919 terrestrial vertebrate species overlapping our sample of <jats:styled-content style="fixed-case">PA</jats:styled-content>s, we estimate that only 4–9% of terrestrial amphibians, birds, and mammals are sufficiently represented within the existing global <jats:styled-content style="fixed-case">PA</jats:styled-content> estate, when only adequately resourced <jats:styled-content style="fixed-case">PA</jats:styled-content>s are considered. While continued expansion of the world's <jats:styled-content style="fixed-case">PA</jats:styled-content>s is necessary, a shift in emphasis from quantity to quality is critical to effectively respond to the current biodiversity crisis.</jats:p>