Beginning about 4000 years ago, American Indians began controlled burning in the Mammoth Cave area. Scientists can see evidence of these burns by examining plant pollen preserved in pond sediments which provides a record of vegetation types through time. This practice of controlled burning was commonly done to improve grazing and therefore hunting. American Indians also burned on the uplands in oak-hickory forests, thinning the stands enough to let sunlight in for the growth of plants that they had domesticated for food and other uses. False Foxglove, a flowering plant, must attach its roots to oak tree roots to live, but it also needs sunlight to grow tall. Stems of this plant were used to make torches to light the way in caves where prehistoric people mined sulfate minerals.
As forests were partially replaced with grasslands, a tremendous variety of prairie grasses and broadleaf plants spread into the area. Annual burning of these grasslands by American Indians continued until the mid 1700s, when the area was settled by people of European and African descent. Longhunters, who came over the Appalachians before European settlement to hunt large game, thought the treeless areas were infertile and so they called them “Barrens”. Part of Mammoth Cave National Park is in Barren County, which got its name from this misunderstanding. The soil was not infertile; there were treeless areas because of annual burning, which killed back saplings and maintained the more open Barrens grassland. As settlement progressed, fire was used less and the native grassland species in pastures were replaced with non-native grasses.
In prehistoric times, Barrens covered thousands of square miles in central Kentucky and Tennessee. Today, the park has two small remnants of Barrens that are being maintained by prescribed fire. You can see the Barrens in the park along sections of the Mammoth Cave Railroad Bike and Hike Trail, to the south and north of Diamond Caverns.
2020 Burn the Barrens Prescribed Fire
March 2020 - Wildland firefighters set a prescribed fire in the barrens area of the park.
NPS Photo/ Rick Olson
September 2020 - Native plants return stronger after the prescribed fire.
NPS Photo/ Rick Olson
Today, we use prescribed fire for multiple reasons:
Maintenance of the tremendous diversity of grasses and wildflowers in the Barrens
Preventing oak-hickory forests from being taken over by beech and maple trees
And reducing hazardous fuels such as downed trees, branches, and leaf litter
Prescribed fires are carefully planned, and monitoring plots are established before the burn so that the effects of the fire can be measured. Goals are set for the prescribed fire, and then fire effects monitoring data tell us if the goals were reached.
Exotic Invasive Plants and Fire
Exotic invasive plants are plant species that are non-native to the area and have arrived to the park by some means such as wind, water, wildlife, or humans. The park knows of about 170 species of plants that arrived from somewhere else, and roughly 100 of those are considered invasive. Invasive species will displace and outcompete native species.
Fire in some cases can remove exotic plants, but in other cases the growth of these plants can actually be promoted by fire activity. Fire managers take special consideration of exotic species when planning prescribed fires. Some species of exotic plants can be controlled by using prescribed fire during the early growing season to burn before the plants have set seed. For example, controlled burns in late September can be good for wiping out Microstegium, an Asian grass, while it is still in its growing season and before it sets seed in October. Other times, applications of chemical spot treatment of exotic plants may be used in the early green-up stages and again during post burn when the plants are small and easy to spot.
Wildfire and Safety
The Mammoth Cave region has not had a catastrophic wildfire in documented history. However, that does not mean it cannot happen. Major wildfires have long been a problem in the western U.S., but in recent years there have been significant wildfires in the East. For example, in November 2016 the Chimney Tops 2 Fire started in Great Smoky Mountains National Park and spread to areas outside the park.
Mammoth Cave National Park has agreements with local fire departments to work together in response to wildfire. This can mean putting out small wildfires, or it may mean containing it so that further risk is prevented. In some cases, if a wildfire does not pose a threat to life or property, if weather conditions are preferable, and the fire can be contained, the park management may choose to allow the wildfire to burn for the benefit of the parks resources. This decision would be made via recommendations from fire professionals to the Park Superintendent.
Wildfires can be both natural or human caused, intentional or otherwise. Lightning is a major cause of ignitions in the western united states, but in this area’s humid midwestern climate, lightning is more often accompanied by rain, so lightning strikes have rarely caused fires, and none of record spread. That being said, the Mammoth Cave region has had severe droughts in recent decades and climate change models indicate that both storms and droughts could increase in severity. Looking to the future as our climate changes, fire management will continue to play a role in preserving Mammoth Cave National Park.