Caves and Karst on the Hoosier National Forest

The Hoosier has special underground values that are largely hidden from view and unrecognized by most Forest visitors. The Forest is located on an area rich in caves and karst features.  Karst is a term that comes from an area in Yugoslavia called the Carso Plateau where scientists first documented these features, and it typically refers to a landscape pockmarked with sinkholes, may be underlain by caves, and has many large springs that discharge into stream valleys. 

Karst landscapes form when rain water seeps down through a relatively thin soil cover and into fractured and soluble bedrock.  Weak acids in rain water that filter down through vegetation and soils easily erode limestone.  The acid slowly dissolves the limestone and creates voids.  These voids gradually enlarge as underground watermoves through them.  Over time, the interaction of water and stone creates blind valleys, caves, gulfs, rises, sinkholes, sinking streams, springs, swallow holes, and other karst features.

Caves and Karst

Cave environments, by their very nature, provide a unique ecological system.  Indiana has one of the best-known karst areas in the United States.  Well over 100 studies have been published on karst features within the State, many of these in the area of the Forest.  Additionally, caves provide excellent natural classrooms for environmental education of unique underground resources and the interrelationships between the surface and subsurface. 

Entering caves on the Hoosier National Forest is prohibited between the dates of September 1 and April 30th each year. These restrictions are necessary to protect federally endangered bat species who hibernate in the caves during this time of the year. While white nose-syndrome has spread through bat populations in Indiana, these closures are in place to protect habitat for these species during this sensitive time. 

Indiana's Karst Regions

The karst region in southern Indiana is divided into two parallel areas called the Mitchell Plain (the eastern one third) and the Crawford Upland in the west.  The Upland is technically less than 100 feet higher than the plain, so the division is not obvious to most; but underground the rock layers are significantly different. 

Layers of rock (limestone, sandstone, and shale) over 400 feet thick were built up by ancient seas that once covered this part of Indiana.  The lowest and thickest layers are limestone up to 170 feet thick.

Over time, massive rock beds tilted and developed cracks and faults.  Erosion has worn away the upper layers in the Mitchell Plain, exposing the geologically older limestones.  Here the karst features such as sinkholes and disappearing streams are common elements of the landscape.  It is here that towns such as Bedford, Bloomington, Mitchell, and Oolitic developed around the limestone quarry industry.  It is also here one can find the majority of Indiana's 2,500 caves.

Plants and Animals of Karst Areas

Several uncommon plants and animals have at least part, if not all, of their life cycle dependent on the environment provided in caves.  Cave life exists in a finite space without light.  Caves provide air, food, humidity, temperature, and water in a normally steady state.  Major changes to this delicate environmental balance are disastrous to many of these uncommon plants and animals.

Cave environments provide habitat for a considerable number of invertebrate species. The description and inventory of karst fauna on the Hoosier is a distinctly recent achievement.  Undertaken to acquire baseline inventories, this work continues to describe species new to the scientific literature and to document new distributions of previously described species. 

While this work represents a remarkable achievement in the description of karst species and their distribution, science still knows little of their life histories and vulnerabilities.  Due to the extreme isolation and harsh conditions of the cave environment, many of the species, especially cave obligates, are rarely found. 

Why Protect Caves?

Caves provide a source of recreation for people that enjoy the dark mysteries of the underground world. Yet, caves are Indiana most remote and fragile ecosystems harboring a variety of wildlife species. Cave formations, such as stalactites and stalagmites, take centuries to form and just seconds to destroy.

Due to the extreme isolation and harsh conditions of the cave environment, caves provide habitat for an array of unusual and rare animal species, including federally endangered species. Perhaps the most fascinating of all animals found in caves are troglobites those that live permanently and exclusively in caves. These unique animals often have no pigment in their skin and lack eyes.

During inventories of caves on the Hoosier National Forest, over 54 troglobitic species were found and over 30 species new to science were discovered. If the cave environment is damaged or altered, the survival of these species is threatened. Caves are intimately linked to the surface. Delicate cave ecosystems require water, air, and nutrients in constant quantities from surface sources. Because caves are connected to the surface, we can not protect them without protecting the lands that contribute water and nutrients to them.

Protecting Our Drinking Water

Everyone knows the saying, what goes up, must come down; But have you heard, what goes down, must come back up?; In karst terrains, rivers and streams often continue underground, draining rapidly into caves with virtually no filtering. This water and the contaminants it carries such as human and animal waste, fertilizers, and pesticides, often travel great distances underground. Eventually, this water emerges back at the surface at springs, seeps, and wells. To protect our drinking water, we must wisely manage the relationship between karst and water by keeping pollutants from entering into caves.

The cave and karst program on the Hoosier National Forest is committed to cave conservation, and minimum-impact caving techniques to protect caves and valuable cave resources for future generations. The Federal Cave Resources Act of 1988 states that federal agencies will, secure, protect, and preserve significant caves on Federal lands for perpetual use, enjoyment, and benefit of all people. As directed in the act, the location of all known caves is kept confidential to protect sensitive resources. This program provides for intensive survey and study of caves for effective management and protection.

Partnerships

Volunteers are the backbone of the cave and karst program on the Hoosier. The Indiana Karst Conservancy and Indiana Cave Survey volunteer thousands of hours each year surveying and mapping caves. They also assist with a variety of cave projects including the film, Caves: Life Beneath the Forest.

Volunteer cavers prepare to descend into a cave on the Hoosier National Forest to collect data on the geology, biology, mineralogy, hydrology, and scientific value of the cave.

Contact

Steve Harriss - Wildlife Biologist/Karst Coordinator, Hoosier National Forest; scharriss@fs.usda.gov; 812-276-4759