Cave micro-climate and tourism: towards 200 years (1819 – 2015) at Postojnska jama (Slovenia)

: Modern tourism at Postojnska jama (the Cave of Postojna) is approaching its 200th anniversary. Besides being an iconic trademark of destination tourism, the cave has a rich history of karstological and speleological investigations, and is also known as the cradle of speleobiology. Since 2009 systematic studies of cave microclimate and biology have been taking place to help provide guidelines for sustainable use of the cave and to mitigate the side effects of long-term tourism. Natural and anthropogenic impacts on cave micro-climate are being evaluated. The entrance to the cave used by tourists was artificially opened in 1866, and this has caused the cave to be well ventilated deep inside. This has both positive and negative influences on the cave environment, allowing the outside climate to impose a strong influence on the cave micro-climate. Statistical comparisons between historical cave air temperature (1852; 1933–1937) and the results of modern monitoring (2009–2013) show that the former average daytime cave air temperature for the inner part of the cave of between 7.5–8.4°C was about 2°C lower than present temperatures. The increase is mostly attributed to changes in natural climatic conditions, because the mean annual exterior air temperature has been increasing for several decades. To a lesser degree the cave air temperature increase can also be attributed to the higher number of tourist visits, when cumulative effects were observed. Successful management of the show cave must combine communication and interaction between researchers, cave owners, cave managers, the public and the State government