Forests contribute to the global climate system by both emitting and absorbing carbon dioxide (CO2) from the atmosphere. However, our understanding of the transfer of CO2 between forests and the atmosphere at specific locations has often been hampered by a lack of data. Newly available maps of how much carbon forests absorbed and released between 2001 and 2020 allow more localized estimation of the carbon emitted from and sequestered by forests. Combining these maps from research led by the World Resources Institute with site-level monitoring information from the state of conservation reporting process of the World Heritage Convention and the IUCN World Heritage Outlook of 2020, the gross and net carbon absorbed and emitted by UNESCO World Heritage forests between 2001 and 2020 have been estimated for the first time and the causes of emissions from some sites determined.