Nadja Zupan Hajna, Karst Research Institute ZRC SAZU, International Union of Speleology (UIS)
On 12 November 2025, the UNESCO General Conference proclaimed 13 September as the International Day of Caves and Karst (IDCK). The new International Day provides a permanent global platform for raising awareness of the importance of caves and karst for biodiversity, water resources, geodiversity, scientific research, cultural heritage and sustainable development. Caves and karst systems are often hidden from view, yet they contain unique natural archives and support highly specialised ecosystems, including many endemic and cave-adapted species that depend on stable subterranean environments.
This makes the International Day particularly relevant to the LifeWatch ERIC community, where biodiversity research, long-term observation, data integration and the study of specialised habitats are central themes. Subterranean ecosystems are especially vulnerable to environmental change, pollution, changes in groundwater conditions, land use and other human pressures. Better knowledge of these environments is therefore essential not only for understanding their exceptional biodiversity, but also for their effective conservation.
The initiative for the International Day originated within the International Union of Speleology (UIS) and grew out of the successful International Year of Caves and Karst 2021–2022. The process was led by Nadja Zupan Hajna of the Karst Research Institute ZRC SAZU, who, as UIS President from 2022, made formal UNESCO recognition of caves and karst one of the main goals of her mandate and coordinated the preparation of the proposal, its scientific justification and the building of broad international support. The Republic of Slovenia subsequently submitted the UIS proposal through the formal UNESCO procedure. The initiative ultimately received wide international support and established 13 September as an annual day dedicated to caves and karst.
The first global celebration of the UNESCO International Day of Caves and Karst took place in Postojna, Slovenia, from 10 to 13 September 2026. It was jointly organised by the Karst Research Institute ZRC SAZU and the International Union of Speleology (UIS), with the support and cooperation of the Slovenian National Commission for UNESCO and Slovenian partner institutions. The events were held under the patronage of UNESCO and the honorary patronage of the President of the Republic of Slovenia, Dr Nataša Pirc Musar, who personally attended the central ceremony in Postojna Cave and addressed the participants.
At the heart of the programme was the international scientific conference “Explore, Understand and Protect: Towards Sustainable Management of Caves and Karst”, which brought together around 160 participants from 35 countries on five continents. Scientific sessions addressed biodiversity and geodiversity, cave and karst protection, groundwater management, climate change, pollution, geohazards, new research technologies, education and sustainable management. The central celebration in Postojna Cave brought together participants and invited guests from 43 countries.
The first celebration in Postojna was only the beginning. The aim is for 13 September to become an annual global opportunity to explore, understand and protect caves and karst, connecting researchers, cavers, conservationists, educators, local communities and decision makers. For biodiversity initiatives such as LifeWatch ERIC, the IDCK also offers an important opportunity to make the often-invisible diversity of subterranean ecosystems more visible and to strengthen cooperation between research, monitoring and conservation.
Text by Nadja Zupan Hajna, Group picture by Valter Leban, taken during the first global celebration of the UNESCO International Day of Caves and Karst in Postojna, Slovenia.
More info and gallery: https://izrkp.zrc-sazu.si/en/novice/the-main-ceremony-marking-the-first-celebration-of-unesco-international-day-of-caves-and









