Up to third of Slovenian caves polluted, but situation improving

According to the Slovenian Speleological Association, 14,695 caves were registered in Slovenia in July and every year at least 300 new ones are discovered. In recent years, more than 500 new caves have been discovered a year.

The cave registry, managed by the association and the ZRC SAZU's Karst Research Institute since 1947, is one of the oldest such projects in the world.

Tičar from the ZRC SAZU's Anton Melik Geographic Institute studied data from the archives using modern technology about the situation in 6,965 caves in 17 Slovenian regions finding that more than 2,500 of them, or 20% of all caves in the country, are polluted.

He warns that the actual share is almost certainly much higher, as in some areas, for example north of the Celje basin, as many as 57.5% of the caves are polluted. He estimates the realistic share of polluted caves could be up to 30%.

"In general, caves were used as waste dumps and are more polluted if located near villages and roads," he told the STA.

The first records of cave pollution date back to 1689, when the celebrated polymath Janez Vajkard Valvasor wrote about it in his Glory of the Duchy of Carniola.

With the turn of the 19th century, this problem began to increase and after WWII people suddenly had more goods while there was still no systematic waste collection.

When litter started piling up, people found the most convenient solutions and karst caves and pits unfortunately proved to be very handy.

The most waste was dumped into the caves until the 1990s, but the garbage remains there and is still an issue, Tičar said.

It includes everything from household waste to construction material and even vehicles. Potentially the most dangerous waste are pesticides, electronic devices, industrial oils and other fluids, and unexploded ordnances.

Absolutely the most polluted cave is Ravnica near Pivka in the southwest, where as many as 4,000 cubic metres of waste have been dumped. The cave is to be cleaned soon, which will be an important step, he said.

Although caves are no longer being polluted to such an extent as in the past, individual cases of pollution still occur. Once such example is a waste water treatment plant in Bloke, which occasionally releases access water into a local underground water source.

"That is when we have problems in Križna Cave, an underground gem, which we very much protect and which is a very well preserved cave. In this case, foam shows in the water in the cave, which indicates pollution," said Tičar, calling for systemic solutions.

The process of cleaning caves is very demanding and must be conducted by well trained cavers. They are mostly volunteers, cleaning the caves as part of annual clean-up campaigns organised by local caving associations.

However, caves that have been polluted for decades do not get cleaned as more people, infrastructure and financial support would be needed for such projects. "This is why we are striving to find systemic solutions at the state level, which would allow for part of the funds to be allocated to returning these habitats into their original state and tackling even the most critical cases of cave pollution."

According to Tičar, the legal foundation for this already exists in the 2004 underground cave protection law, a unique piece of legislation in the world, which defines caves as a natural asset of national importance, which is a very high level of protection.

The law also includes provisions on monitoring the situation in the caves and punishing polluters, and defines the need for an operative clean-up programme.

Although a direct connection between cave pollution and underground water pollution has not been experimentally confirmed yet, experts agree this connection is very probable. In a time when the supply of clean, drinking water is becoming a growing global issue, a systematic clean-up of polluted caves is becoming a must.

As part of his PhD theses, Tičar created a model for a priority clean-up of caves, which enables a systematic system to solve the most critical pollution issues caused by cave pollution. It envisages making a list of the most critical sites of the 2,500 polluted caves that should be cleaned up as a priority to prevent major contamination of underground water.

It also gives guidelines for clean-up campaigns organised by caving associations or others and proposes cooperation with the Environment Ministry.