Mount Rushmore National Park plays host to a rich and diverse ecosystem, yet it grapples with a wide selection of environmental stressors. From disturbances like air tour noise and air quality concerns to the persistent threats of forest fires, Mountain Pine Beatle infestation, and invasive species, the park confronts a range of conservation challenges. Moreover, Mount Rushmore faces inherent natural geological issues, which, in turn, threaten the structural integrity of the iconic national monument of the four presidents.
Biodiversity on Mount Rushmore
Within the scenic expanse of the Black Hills in South Dakota lies Mount Rushmore National Park, a haven for wildlife, characterized by a varied terrain of forests, rocky outcrops, streams, and wetlands. Taken together, the diverse terrain of Mount Rushmore collectively nurtures a vibrant ecosystem.
Notable features of Mount Rushmore’s terrain include pristine old-growth Ponderosa Pine Forest and the Starling Basin wetland complex. These areas serve as vital habitats for the conservation of various species, such as amphibians, bats, butterflies, and reptiles. Of particular note is the continued presence of the Northern Leopard Frog, a species in decline across much of North America but still common in the Starling Basin. Similarly, the forests of Mount Rushmore harbor a plethora of birds. The Red-Breasted Nuthatch, Yellow-Rumpled Warbler, and the continued presence of the Brown Creeper – according to the USDA Forest Service (2005) – indicate an abundance of mature, healthy, coniferous forest.
Environmental Stressors
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Sign up to our Free Weekly NewsletterWhen it comes to conservation and the challenge of environmental stressors, several concerning indicators, such as the condition of old-growth Ponderosa Pine, land cover (encompassing forests and rocky outcrops), and the health of native fish populations, have drawn the attention of scientists.
Mount Rushmore National Memorial is almost entirely surrounded by National Forest. The invaluable stock of live Ponderosa pine trees, like many neighboring National Forests in the Black Hills face a moderate to high risk of infestation by Mountain Pine Beatles – the effects of which can be devastating.
Moreover, the park contends with a further range of environmental stressors including the disturbance caused by air tour noise, air quality issues, the impact of commercial horse trails, and the proliferation of invasive species such as exotic fish and non-native plants. The risk of fires in the park has escalated since the suppression of natural surface fires by European settlement, leading to unnatural tree densities and fuel loads.
Geological issues
The geological formation of the Black Hills, an isolated mountain range in the Great Plains of South Dakota, is the product of the “Laramide Orogeny” – a period of mountain building that began in North America between 60-65 million years ago. Mount Rushmore is among the oldest geological structures of the uplift.
The selection of the vast Harney Peak Granite in the southern Black Hills for the Mount Rushmore Memorial was based on its substantial size, uniformity, and the minimal presence of joints and fractures. For the US National Park Service, preservation of the geological features of the memorial is paramount.
Natural processes such as weathering, and erosion, compounded by human activities such as mining, have led to significant geological challenges. The primary erosive forces acting on Mount Rushmore are wind, precipitation (rain, snow), chemical weathering, and frost wedging. Taken together these erosive forces jeopardize the integrity of the Mount Rushmore National Monument.
Preserving the Monument
The main risks to the monument stem from potential shifts in the granite rockface of Harney Peak and the persistent challenge of frost wedging. Since 1998, Mount Rushmore has had a “Rock Block” monitoring system, designed to detect temperature fluctuations and potential movement within the granite.
Through the identification of twenty-one crucial “key blocks” on the sculpted heads of the four presidents, geologists send data from electronic instruments affixed directly to the sculpture, to a central computer system four times daily. This setup ensures that any movement is promptly detected, thus managing potential risks to the structural integrity of the monument.
Frost wedging poses a more significant threat. As water seems into minute cracks in the granite, it freezes, expands, and exacerbates fractures in the rock. To address this issue, a maintenance crew conducts yearly inspections. Any cracks are promptly filled with silicone sealant to present water infiltration and mitigate risk.
