Pinhook Bog Restoration Project

A small pond at Pinhook Bog surrounded by a forest in mid-August.

NPS photo by Wesley Butler

Pinhook Bog is a 580-acre unit of Indiana Dunes National Park (INDU). Pinhook Bog and the hills surrounding it are part of the Valparaiso Moraine which was left by retreating glaciers some 10,000 years ago. As the glacier was retreating, a block of ice broke off and created a kettle lake. This kettle lake is fed solely by precipitation and the resulting runoff from the surrounding hills. There is no outlet to release the water. The slow decay of plants and retention of water due to there being no outlet has allowed the water to acidify dramatically. The water within Pinhook Bog has a pH around 4 where most lakes and streams in the area have a pH between 7 and 9.

The acidification of the water allowed sphagnum moss to grow and eventually cover most of the surface of Pinhook Bog. The sphagnum mat encouraged other acid-loving plant species to flourish. Many of the plants residing in the bog are more commonly found in northern bogs and even on the Arctic tundra. The floating bog portion of Pinhook Bog supports 167 native species. Many of the species are rare in Indiana but more commonly found hundreds of miles to the north where bogs are far more abundant.

The bog (110 acres) is an example of a quaking bog for how its surface trembles under foot. This is one of the southernmost quaking bogs in North America. In 1965 the bog portion was designated a National Natural Landmark. The Pinhook Bog Unit was purchased by the federal government in 1976 and efforts to protect and preserve this unique habitat began.

 

A closeup of Sphagnum moss in front of a forest of twigs and other plants.

NPS photo by Wesley Butler

Prior to purchase by the federal government, the upland area was a mix of forest and row crop fields. The former landowner operated a U-pick blueberry farm on the floating bog. Blueberry bushes thrive in acidic conditions making the floating bog ideal for blueberry production. The formerly farmed upland areas are now fallow fields which have transitioned to grasslands and new-growth forest. Meanwhile, the blueberry plants on the bog continued to flourish.

Botanical studies performed in 1984 and repeated in 1999 revealed that there was a decline in population size of the rare and unique species on the bog which were being monitored. This change was attributed to competitive pressure from highbush blueberry (Vaccinium corymbosum). It was hypothesized that the decline of bog species and an increase in highbush blueberry and red maple (Acer rubrum) was resulting in a transition of the floating bog to a mesophytic forest which is a broadleaf and mixed forest. The rapid increase in blueberry is not reflective of its behavior at other bogs. The tree community of a bog is typically dominated by tamarack (Larinx laricina) and some spruce and pine species.

 

Park employee pollinating a Pink Lady's Slipper flower.

NPS Photo by Zachary Lindeman

As the unnatural blueberry shrubs and red maple trees increased, the amount of sunlight decreased. This encouraged more shade-loving species at the detriment of the sphagnum and rare plants naturally found on the bog which require abundant sun. There is also a drying effect as the shrubs and trees pull water from the floating mat which inhibited sphagnum growth.

Staff at INDU are charged with protecting the natural resources in the park to insure they are unimpaired for future generations. Resource managers actively manage and mitigate the negative impacts of habitat degradation. National Park employees take this job very seriously and have initiated several projects to protect the unique habitat and rare plants at Pinhook Bog.

INDU is working with a contractor to increase light levels by removing blueberry bushes and red maple trees from the bog. As visitors utilize the boardwalk, they can observe what the bog looks like with the impenetrable and unnatural blueberry thicket versus areas that have been cleared. It is easy to see how light can now reach the floating mat of the bog in the areas where blueberry has been removed which benefits the plants which were formerly suffering from the shade. The red maple trees are girdled to kill them, and most are left standing to provide habitat for wildlife. If they are at risk of falling onto the boardwalk, they are removed.

 

The bog is home to several rare orchid species. When growing under the dense layer of blueberry shrubs, the orchids that rely on insect pollinators suffered because the insects could not easily fly to the flowers. The pink lady’s slipper orchid was one such species on the decline. To assist the species, the lady’s slipper has been hand pollinated by INDU staff for several years. The hope is that by opening up the bog mat by removing blueberry bushes the insects which pollinate the lady’s slipper will again perform the task naturally and the orchid population will increase without human assistance.

Invasive plant species such as reed canary grass, cattail, and phragmites have dominated many wetlands in the area. While these species may not thrive in the highly acidic nature within the bog mat, they have been found around the periphery of the bog where the water is near neutral. Treatments are regularly performed to eliminate or keep these populations in check to preserve the habitat quality of Pinhook Bog.

Prevention efforts are also important in maintaining the quality of the bog and surrounding land. Clean boots and clothing free of plant seeds can reduce the risk of introducing new invasive species to the property. Do not harvest plants from the area or introduce new plants onto the property. To protect fragile plants and the incredible diversity at Pinhook Bog and for your own safety, please stay on the boardwalk onto the quaking bog and the hiking trails throughout the unit. The bog trail and boardwalk onto the bog have restricted access and are only open during ranger-led open houses on summer weekends. For habitat protection, dogs are not allowed on the bog trail and boardwalk and hiking off the boardwalk is strictly prohibited. Dogs on a leash are permitted on the upland trail. Bicycles and motorized vehicles are prohibited on all trails at the Pinhook Bog Unit. The parking lot and upland trail are open daily from 6am to 11pm.