This is an international caving expedition, aiming to explore and study the caves in Mulu National Park, Sarawak, Malaysia. We are going to investigate the connection between caves, underground rivers, and rainforests. The expedition will be held from 1 to 26 July 2019 in Mulu National Park, Borneo Island, Sarawak Province, Malaysia, and is organized by Speleo Club NEPIAST – Bourgas and Bulgarian Federation of Speleology.

Situated in the Malaysian part of Borneo Island, Mulu National Park preserves some of the last unexplored rain forests. The park is extremely difficult to access because of the lack of roads and requires excellent physical training due to the heavily terraced terrain ranging from 50 to 2377 m. The caves of the Mulu Park are characterized by a large volume, labyrinthine nature, and large underground rivers. The largest described cave system is Clearwater with over 227 km of mapped parts by 2018, ranking it third in the world. The Sarawak Hall in the Deer Cave Cave is one of the world’s largest cave chambers. Its size is so great that it’s easy to fit 40 474 boating aircraft. In the caves of the park, there are huge colonies of bats and swifts – several million bats come out each night from the cave Deer cave, representing one of the largest mammalian aggregations, known to science. Despite the numerous studies of the area, much of the park is still unknown, and new discoveries continue to be made annually. Only 10% of the park and 5% of the caves are open for visitors. The remaining 90% of the park territory is still the subject of studies, with some of which we will also contribute with our expedition.

The purpose of the expedition is to explore caves in the karst area of ​​the Mulu National Park in Malaysia, where some of the longest and largest caves in the world are located. The cave systems “Deer cave”, “Clearwater”, “Good luck cave” and others will be visited during the expedition, and a survey of underground ecosystems will be carried out. In addition to exploration, an ecological groundwater study will be conducted during the expedition. Our goal is to trace nutrients from underground rivers to their assimilation into the rainforest. The expedition is part of an international groundwater research project and is supported by international foundations – “National Geographic”, “Bat Conservation International”, “The Explorers club” in partnership with the Bulgarian Federation of Speleology.


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