Gunns Plains Cave

Gunns Plains Cave State Reserve protects one of Tasmania's most significant limestone cave systems, discovered in 1906 and opened to the public as one of the state's earliest cave tourism attractions. The cave is located in the Gunns Plains area of the Forth River valley on the northwest coast, where Ordovician limestone has been dissolved over millions of years to create a network of chambers and passages adorned with stalactites, stalagmites, and other speleothems. The cave also features a rare glow-worm grotto where larvae of the cave fungus gnat (Arachnocampa tasmaniensis) create a constellation of blue-green bioluminescent light. The reserve protects both the cave itself and the surrounding limestone karst surface landscape.

Gunns Plains Cave supports specialised cave-adapted fauna including significant colonies of glow-worms and various invertebrates adapted to the cave's perpetual darkness and stable microclimate. The cave's glow-worm population is the primary biological attraction, with thousands of larvae of Arachnocampa tasmaniensis creating bioluminescent displays that attract insect prey into their sticky threads. Various bat species roost in the cave, and the cave entrance zone is inhabited by cave wetas and other invertebrates that tolerate some light. The surrounding limestone karst surface landscape supports grassland and dry forest communities harbouring diverse invertebrates, lizards, and small mammals.

The cave surroundings include dry sclerophyll forest and coastal heath typical of the Gunns Plains area, with eucalypts, wattles, and native grasses forming the predominant plant communities on the thin, rocky limestone-derived soils. The cave entrance supports shade-tolerant mosses and ferns adapted to the cool, humid transition between the cave interior and the outside environment. The limestone karst surface, where it is exposed, creates distinctive micro-topographic features including sinkholes, limestone pavements, and elevated rocky outcrops that support specialised plant communities adapted to these unusual substrates.

Gunns Plains Cave was formed in Ordovician limestone approximately 480 million years old by the dissolution of calcite by weakly acidic groundwater percolating through cracks and joints. This process, known as karstification, has operated continuously over millions of years to create the cave passages and chambers visible today. Speleothems including stalactites and stalagmites form where calcite-rich water drips or seeps through the cave walls and floor, precipitating calcite as carbon dioxide is released. The cave system is part of the broader limestone karst of the Forth River valley, which includes multiple cave systems and surface karst features including dolines.

The Gunns Plains area experiences northwest Tasmania's maritime climate, with moderate rainfall averaging around 1,000 millimetres annually and mild, maritime-influenced temperatures. The cave interior maintains a stable temperature of approximately nine degrees Celsius and near-100 percent relative humidity year-round, independent of external conditions. The stable cave microclimate is essential for the glow-worm population and the formation of speleothems. Visitors to the cave should bring a light jacket regardless of external temperatures, as the cave interior can feel cold even in summer.

The cave was known to the local European farming community before its formal discovery and first recorded exploration in 1906. The cave's glow-worms and stalactites quickly attracted public interest, and guided tours were established in the early twentieth century, making Gunns Plains one of Tasmania's earliest natural tourism attractions. The cave has been visited by generations of school groups, tourists, and local families, and it retains a place in many Tasmanians' childhood memories as an early nature experience. The history of the cave as a tourism site reflects the broader pattern of Tasmanian cave tourism development from the early twentieth century.

Gunns Plains Cave was reserved in the early twentieth century, making it one of Tasmania's earliest cave reserves, reflecting recognition of the cave's tourism and natural heritage values from very early in the conservation history of the state. The reserve has been managed for cave tourism for over a century, during which time visitor facilities have been progressively upgraded while maintaining the cave's natural character. The cave is managed as a partnership between the tourism operation and Parks and Wildlife Tasmania.

Guided tours of Gunns Plains Cave are the primary attraction, taking visitors through the cave's chambers and passages to view stalactites, stalagmites, and the celebrated glow-worm grotto. Tours operate at regular intervals throughout the day and take approximately one hour. The glow-worm display, where thousands of larvae illuminate the cave ceiling with bioluminescent light, is a highlight of the tour. The cave temperature remains constant at around nine degrees Celsius, providing a refreshing escape on hot summer days. The surrounding karst landscape can be explored on short walking tracks from the cave entrance.

Gunns Plains Cave State Reserve is located approximately 30 kilometres south of Ulverstone on the road to Gunns Plains via Forth. The cave visitor centre provides ticketing, interpretation, and toilets, and the cave is open for tours throughout the year. A national parks pass is required in addition to the cave tour fee. The surrounding area offers picnic facilities. The cave is easily combined with visits to Leven Canyon, the Dial Range, or other attractions in the northwest region. Ulverstone and Devonport provide accommodation and full visitor services.

Conservation management of Gunns Plains Cave focuses on protecting the glow-worm population and speleothem formations from the impacts of visitor numbers and lighting. Strict protocols limit photography with flash, regulate group sizes and visit duration, and ensure appropriate lighting systems are used within the cave. The glow-worm population is sensitive to disturbance, and maintaining the cave microclimate with minimal ventilation changes is important for both the glow-worms and speleothem preservation. Water quality entering the cave from the overlying karst is monitored, as agricultural chemicals from surrounding farmland can enter the cave system via groundwater.