Cave clean up

Removing toxic waste to help unique creatures of the underworld

In Croatia, there is a huge network of submerged caves that is recognized as a global hotspot for subterranean biodiversity. The animals that have adapted to live in this underground world are unlike anything you may find above the surface. For centuries, waste has been dumped into some of these caves, seriously threatening its precious inhabitants and contaminating an important source of drinking water. Our goal is to start reversing the damage and safeguard the future of these unique species, as well as prevent further contamination. Partnering with expert cave biologists and cave divers from the Croatian Institute for Biodiversity, we will undertake a two-part operation to remove the most dangerous materials. Find out more on why we are doing this to save miraculous animals like the olm.


Project Timeline

June 2021

Cave clean up operation takes place

The Intervention

Arrive at the site of this project and it‚Äôs easy to image you‚Äôve deliriously found yourself at the aftermath of a tsunami. The shocking scene of waste and scrap that is tangled and stacked forms a mountain at the cave‚Äôs mouth. Our team we were compelled to act. This project will fund an operation to remove the most hazardous items of waste from the cave ‚Äď home to an array of fascinating threatened cave animals.

The history of this site and how it came to accumulate about 16 cubic m3 of solid waste, is a familiar one of neglect of the natural world. Rummage through the mess and you will find an assortment of modern society’s mark: plastics, metals, rubber, wood, and domestic appliances. In the past, attempts at gaining funding for this set of magnificently unique species have failed.

Local cavers, who have witnessed the wreckage first-hand, want to take matters into their own hands. They are going to remove the waste that is currently above the water level, using ropes and winches if necessary.

For submerged waste, a more complex operation involving cave divers will be required to bring these large objects to the surface. Much has already been done by the team of divers to reach this point - from research and monitoring to describing new species and direct conservation. They bring a wealth of knowledge, skills, and passion to protect the unexplored underworld - all will be central to this project’s success.

A cave diver partially out of water, with full equipment, putting solid waste into a bag inside a cave. Credit: PROTEUS project team.
Some of the waste in the cave is submerged and will have to be removed by experienced divers. Photo credit: PROTEUS project team.

What your Contribution will do

As Mossy Earth Members you will be supporting the teams of volunteer cavers and cave divers by

  • paying for their¬†food and transport¬†and
  • purchasing their¬†equipment

Given the amount of waste, the intervention is likely to take several days. Even so, it is unlikely that we will be able to remove all the waste in which case the objects deemed more likely to be contaminating will be removed first. Once removed, the waste will be transported to an appropriate recycling plant by truck.


The olm is reliant on clean pure water and water pollution is one of its main threats

Sir David Attenborough in Attenborough's Story of Life, BBC Earth

Learn More About the Context Behind this Project

The Dinaric arc is a cave biodiversity hotspot

The Dinaric arc in South-Eastern Europe is a region characterised by stunning landscapes, from impressive mountain peaks to cascading turquoise waterfalls and a wild Mediterranean coast. Easier to miss however is the fact that this region hosts the largest network of subterranean rivers in Europe and that it is a global hotspot for cave biodiversity. Because it is difficult for cave-adapted animals to move between caves many species have a very narrow distribution and some exist only in a single cave. This is just one of the highlights of a hidden world that deserves to be uncovered and valued instead of disregarded.

A large waterfall of 2 steps ending in a turquoise body of water. The waterfall is surrounded by lush green vegetation.
The karst landscape of the Dinaric ark is stunning with impressive waterfalls and lakes creating a fairy-tale-like scenery.

Unique but forgotten about species

The Rupeńćica-҆mitovo cave system, which is the one we are focusing on, provides habitat for some remarkably interesting species. The¬†olm¬†is probably the most famous among them. It‚Äôs a¬†blind cave salamander¬†that can¬†live up to a century¬†and¬†survive for a decade without feeding. It is among the most evolutionarily distinct amphibians known to science meaning that there is nothing else like it on earth. It is also¬†one of the 10 species that David Attenborough would select to be saved from extinction¬†if he had to choose. Another interesting species found here is the¬†Croatian dace¬†a small freshwater fish species that rely on this habitat to sustain its last remaining population. And a final species that needs mentioning is the¬†Ogulin cave sponge. This is the world‚Äôs only known species of cave-dwelling freshwater sponge and it is known only from a few caves around this area. The importance of saving such species can be likened to our own survival, a more diverse world is a more adaptable one. By protecting all evolutions on the tree of life, we increase our chances of one day benefiting from their distinctiveness. ¬†¬†

Photo of the olm, a blind pale-pink coloured salamander with red protruding gills and a slender body. The animal is resting on a rock in a submerged cave. Photo credit: PROTEUS project team.
Because it has adapted to live in complete darkness, the olm has lost the sense of sight. To hunt small crustaceans it relies on an acute sense of hearing and smell. Photo credit: PROTEUS project team.

Risk of extinction

The current situation is grave: the entire community of organisms in this cave is under threat. This is especially concerning if we consider that many of them are at considerable risk of global extinction.

  • The olm, Proteus anguinus, is classified as vulnerable to extinction, mainly due to the threat posed by water pollution and cave habitat degradation throughout its range
  • The Croatian dace, Telestes polylepis, is classified as critically endangered and appears to be on the verge of extinction with the last small population found inside this cave.
  • The cave sponge, Eunapius subterraneus, was previously classified as endangered and exists only in this part of Croatia but more data is needed about its conservation status.
Ogulin cave sponge, a white living organism attached to a rock with a protruding central opening. Photo credit: PROTEUS project team.
The Ogulin cave sponge used to be present at nearby caves but has recently disappeared. It is thought that water pollution may have been responsible for the loss of those populations. Photo credit: PROTEUS project team.

Water pollution

The lack of awareness of this cave’s (and many others) wonderful and rich biodiversity, has sadly meant local people have treated it as a waste disposal site for centuries. Without this intervention, toxic chemicals will continue to degrade water quality and once these chemicals enter the cave system through the water they can no longer be physically removed and may continue affecting the ecosystem for a long time. On top of this, the submerged caves in this region provide drinking water for the surrounding area and if they continue being contaminated this could end up having negative health consequences.

As improvements in waste disposal and collection in Croatia occur, there is hope that the efforts of the teams involved in this cave clean up will not go unrewarded further down the line. The best we can aim for is not only a turnaround in the security of biodiversity but also a turnaround in mindset towards it.

A caver in a full red suit and helmet abseils over a huge pile of solid waste inside Rupeńćica cave. Photo credit: PROTEUS project team.
The grim situation of the cave entrance in a photo taken a few years ago. Photo credit: PROTEUS project team.

Curious to learn more?

If the world of cave biology intrigues you and you haven’t yet read our article about cave dwelling animals you should check it out!

If you want to learn more about the backstory of why we think it is important to protect bizarre creatures like the olm you can listen to our podcast episode about Mossy Earth‚Äôs ‚ÄúUgly ones‚ÄĚ programme.

Sources & further reading

Peer Reviewed Research Section
  1. ‚ÄúSubterranean Biodiversity Patterns from Global to Regional Scales‚ÄĚ - Zagmajster, M., Malard, F., Eme, D., & Culver, D. C. (2018)External linkIcon Peer Review
  2. ‚ÄúThe morphological variability, distribution patterns and endangerment in the Ogulin cave sponge Eunapius subterraneus Sket & Velikonja, 1984 (Demospongiae, Spongillidae)‚ÄĚ - BilandŇĺija, H., Bedek, J., JalŇĺińá, B., & Gottstein, S. (2007)External linkIcon Peer Review
Heart Image

the team behind the project

Team Member

Tiago de Zoeten, conservation biologist at Mossy Earth

Team Member

DuŇ°an Jelińá, researcher at the Croatian Institute for Biodiversity