Caves and karst in global sustainability: The case for an international day

Karst landscapes and cave systems are among the most ecologically, hydrologically, and culturally significant environments on Earth. They supply drinking water to nearly 20 % of the global population and preserve invaluable records of palaeoclimate, archaeology, and biodiversity. Yet these subterranean systems remain largely invisible in environmental governance and sustainability discourse. Karst aquifers represent critical but overlooked nature-based solutions for water security and climate resilience, buffering floods, sustaining dry-season flows, and supporting unique subterranean ecosystems. However, they face growing threats from land-use change4, pollution, infrastructure development, and climate change, exacerbated by limited legal recognition and monitoring. In response to this policy gap, the International Union of Speleology (UIS) launched the initiative for an International Day of Caves and Karst (IDCK), following the success of the 2021 International Year. As of 2025, the proposal is endorsed by more than 70 national institutions, international organisations, and UNESCO site managers, with increasing support from governments and Indigenous nations. A formally recognised IDCK would mainstream caves and karst into global environmental agendas, strengthen science–policy interfaces, and advance protection of subterranean environments across biodiversity, water, and heritage frameworks.