UNESCO International Day of Caves and Karst

News

• IDCK Celebration ¡Call for Abstracts!

Join us in Postojna, Slovenia, for the international scientific conference:

"Explore, Understand and Protect: Towards Sustainable Management of Caves and Karst", 10–13 September 2026

The conference is part of the first celebration of the UNESCO International Day of Caves and Karst (IDCK) and will bring together researchers, cave and karst experts, educators, managers, and conservation professionals from around the world.

Keynote speakers include:

• John Gunn (UK),

• Zoran Stevanović (Serbia),

• Ilias Valiakos (Greece),

• Marlene Liddle (Haida Gwaii, Canada),

• Franci Gabrovšek (Slovenia)

Abstract submission deadline extended to July 10

Registration remains open until 1 September 2026

For more information: izrkp.zrc-sazu.si/en/dogodki/international-day-of-caves-and-karst-idck 

The program includes scientific sessions, excursions to some of Slovenia’s most important karst sites, and participation in the first official celebration of the UNESCO International Day of Caves and Karst in Postojna Cave on 12 September 2026.

IMPORTANT: Accommodation availability in Postojna is becoming limited. Participants are encouraged to register and book accommodation as early as possible. If you need assistance finding accommodation, please contact the local travel agency Kompas Postojna:  https://www.kompas-postojna.si/index.html

¡We look forward to welcoming you to Postojna!

• Invitation to the First Celebration of the International Day of Caves and Karst (IDCK)

Dear colleagues,

We are pleased to invite you to participate in the events marking the first celebration of the UNESCO International Day of Caves and Karst, to be held in Postojna, Slovenia, from 10 to 13 September 2026.

These events represent the symbolic and official launch of the global observance of the International Day of Caves and Karst, proclaimed by UNESCO in 2025. Please find attached the invitation and the preliminary programme of events, which will be held under the honorary patronage of the President of the Republic of Slovenia, Dr Nataša Pirc Musar, and under the patronage of UNESCO, with the support and cooperation of the Slovenian National Commission for UNESCO, Postojna Cave, Škocjan Caves Park, the Municipality of Postojna, the Municipality of Pivka, and the Speleological Association of Slovenia.

For more information and registration for the scientific conference and the official ceremony in Postojna Cave, please visit:

https://izrkp.zrc-sazu.si/en/dogodki/international-day-of-caves-and-karst-idck 

Information on registration for the accompanying events and their detailed programme will follow.

We look forward to your participation and to celebrating the beginning of this important global initiative together.

Kind regards,

Nadja Zupan Hajna

on behalf of the Organising Committee

Karst Research Institute ZRC SAZU and International Union of Speleology (UIS)

• The First Celebration of the International Day of Caves and Karst (IDCK), proclaimed by UNESCO will be in Postojna, Slovenia: 10–13 September 2026

Following the proclamation of the International Day of Caves and Karst (IDCK) by UNESCO, the first official celebration is planned to take place in Postojna, Slovenia, in September 2026. The central date of the celebration will be 13 September 2026, with a series of scientific and outreach events planned in the days leading up to it.

Preliminary programme outline (subject to confirmation): 

• • 10 - 12 September 2026 – International conference in Postojna.

Theme: Sustainable management of caves and karst, with a focus on protection, education, and research as a foundation for sustainable development, and scientific excursion to selected karst and cave sites 

• • 12 September 2026 (Saturday evening) – Official IDCK celebration event in Postojna Cave (to be confirmed)

  •  13 September 2026 – International Day of Caves and Karst.

Details regarding the conference programme, invited speakers, co-organisers, and registration will be announced in due course.

Organisers (preliminary): with the support of the Slovenian National Commission for UNESCO,  International Union of Speleology (UIS),  Karst Research Institute ZRC SAZU, Slovenia .....

We warmly invite all supporters of the International Day of Caves and Karst initiative, as well as the wider scientific, educational and policy communities, to save the date. A formal announcement, registration form and detailed programme will follow.

• UNESCO proclaims the International Day of Caves and Karst!

At the General Conference of UNESCO in Samarkand (12 November 2025), 13 September was officially proclaimed the International Day of Caves and Karst — a global recognition of the significance of the hidden world beneath our feet.

The initiative was proposed to UNESCO by the Republic of Slovenia, following the proposal of the International Union of Speleology (UIS), in close cooperation with the Slovenian National Commission for UNESCO, the Permanent Delegation of Slovenia to UNESCO, and the Karst Research Institute ZRC SAZU, where the UIS headquarters has been based in Postojna, Slovenia.

Caves and karst cover nearly one quarter of the Earth’s land surface and provide drinking water to over a billion people. They preserve unique subterranean biodiversity, geological archives, and invaluable cultural heritage. Yet, they remain among the least understood and most fragile ecosystems on our planet.

The International Day of Caves and Karst will help raise global awareness, promote research, education, and international cooperation in science, environmental protection, culture, and sustainable tourism.

The UIS warmly thanks all UNESCO Member States that supported the initiative, as well as the UNESCO scientific programmes (IGGP, MAB, IHP) and international partners including the International Science Council (ISC), IUCN, and more than 150 organizations worldwide that endorsed the proposal. Our sincere appreciation goes to the Slovenian National Commission for UNESCO and the Permanent Delegation of the Republic of Slovenia to UNESCO in Paris for their dedicated diplomatic efforts and continuous support.

From now on, September 13 will unite the global cave and karst community in celebrating and protecting these vital landscapes — for science, for nature, and for humanity.

Don’t forget, in 2026 we will celebrate the first ever International Day of Caves and Karst on 13 September!

Nadja Zupan Hajna, UIS Past President
November 12, 2025

• PAPER ON IDCK
  A paper about the IDCK initiative by Nadja Zupan Hajna has been published in Nature-Based Solutions (Elsevier):Caves and karst in global sustainability: The case for an international day
  The article highlights the vital role of caves and karst systems in water security, climate resilience, biodiversity, and cultural heritage, while emphasizing their limited visibility in global sustainability policies. It presents the initiative for the International Day of Caves and Karst (IDCK), coordinated by the International Union of Speleology (UIS) with the support of the Slovenian National Commission for UNESCO, and endorsed by many national and international institutions.
  October 27, 2025

• OUTLOOK
  The official proclamation of the IDCK by the UNESCO General Conference is expected in November 2025 in Uzbekistan.

• GOOD NEWS OF UNESCO EXECUTIVE BOARD
  I am very pleased to share that the UNESCO Executive Board has today adopted the decision on the International Day of Caves and Karst (IDCK) — co-sponsored by 59 countries! The final proclamation will take place at the UNESCO General Conference this November in Uzbekistan. Let’s keep our fingers crossed for a positive outcome and for global recognition of caves and karst!
  October 9, 2025  Nadja Zupan Hajna, UIS Past President
  
  

• UNESCO UPDATE
  The Slovenian Embassy intends to submit the proposal for the International Day on the agenda of the UNESCO Executive Board meeting by the end of this week. They are continuing intensive lobbying with States for both support and co-sponsorship. The initiative will be considered by the Member States of the Executive Board (58 members) at their autumn session, which will take place between 1 and 16 October 2025.
  We kindly ask you to inform your UNESCO Delegation and/or Ministry(Ministries) about the importance of this initiative and to encourage them to vote in favour of the IDCK proposal at the UNESCO Executive Board in October and, if approved, also at the UNESCO General Conference in Uzbekistan this November (more information see Support).
  September 11. 2025
  
  

• IDCK VIDEO
  The official video for the International Day of Caves and Karst will be published on this website on September 13, 2025. Stay tuned.
  September 5, 2025
  
  

• START
  The International Union of Speleology (UIS) proposed to the UNESCO Secretariat the proclamation of the International Day of Caves and Karst. On 29 May 2025, the Government of the Republic of Slovenia officially decided to support the UIS Initiative. The Republic of Slovenia is actively lobbying to secure co-sponsorship from other UNESCO Member States.
  The Proposal is scheduled to be submitted to the UNESCO Executive Board by the Government of Slovenia. A final decision is expected during the UNESCO General Conference in November 2025.
  July 27, 2025

Support

Inform your national UNESCO delegations or government authorities about the proposal and kindly request their support during the voting process.

Explanatory note

How to contact UNESCO delegations
Support letter example 

List of supporting organizations

Impact 

• Raise global awareness of karst systems and caves

• Support of all UN Sustainable Development Goals (SDGs), especially
  - SDG 6 Clean water from karst aquifers
  - SDG 11   Safer urban development in karst-prone zones
  - SDG 13 Climate action via paleoclimate records
  - SDG 15 protection of subterranean biodiversity

• Inspire youth education, public outreach, and science diplomacy

• Strengthen international partnerships and knowledge sharing

• Encourage policy reform and cross-sectoral cooperation

• Promote sustainable tourism

September 13

• The proposed date does not favour any nationality, country, or professional association that already celebrates cave- or karst-related events on other dates.

• It celebrates the founding month of the International Union of Speleology (UIS).

• Weather conditions in early September support global events. The date is not already assigned within the UN system.

• It commemorates the historic first UIS presentation at UNESCO in Paris on 13 September 2021.