The UNESCO World Heritage List comprises 1223 sites of outstanding universal value classified as natural, cultural, or mixed. However, only 40 sites (3%) are classified as mixed, highlighting a persistent challenge within the World Heritage Convention to recognize the interconnection between nature and culture. Furthermore, although 129 (11%) of sites are designated as Cultural Landscapes, exemplifying significant human-environment interactions, only 10 of these are mixed, reflecting a stronger emphasis on the cultural criteria. To address this nature-culture divide, we evaluated the explicit recognition of biocultural value within the World Heritage Sites. Using a recent definition of biocultural heritage, we leveraged large language models (LLMs) to reassess the classification of sites based on their official descriptions in the World Heritage List. Our findings reveal that up to 26% of the sites could be reclassified as biocultural, indicating that a substantial number of sites hold previously unrecognized biocultural value. Therefore, we advocate for a comprehensive biocultural reclassification of the World Heritage Sites, and suggest this effort could advance UNESCO's vision toward a representative, balanced, and credible World Heritage List, which has not been achieved so far.