Bringing Back a Dune Wetland: Indiana Dunes' Restored Panne

Wildflowers in the restored panne — a sign of the biodiversity that has returned. NPS.

A rare dune wetland at Indiana Dunes National Park has been restored after being overrun by invasive plants — the work of the park and the NPS Great Lakes Invasive Plant Management Team (IPMT).

What's a panne?

A panne is a wetland between sand dunes — an intradunal wetland. Wetlands are among the most biodiverse ecosystems, supporting many plants and animals, cleaning water, and controlling floods and erosion. Pannes are globally vulnerable and home to many endangered and at-risk species, so they're a priority at Indiana Dunes.

The odds

One of the pannes at popular West Beach was overwhelmed — and as a seed source, it threatened the park's healthy pannes. Small pockets of native plants gave hope.

• 2005: the park began monitoring and inventory.
• 2009: the park partnered with the Great Lakes IPMT to control the invaders: common reed (Phragmites australis), hybrid cattail (Typha × glauca), purple loosestrife (Lythrum salicaria) and nonnative thistles.

Common reed swallows a member of the Great Lakes Invasive Plant Management Team. NPS.

• Common reed: a grass 1–6 meters tall (up to 20 feet), forming a dense monoculture through rhizomes — underground stems that sprout new plants and make non-chemical control nearly impossible in established stands. Dead reeds had to be knocked down each year to reach the next season's growth.
• Hybrid cattail (a cross of narrow-leaved and broad-leaved cattail) and purple loosestrife also spread by rhizomes into dense stands, and leave seeds that last decades in the soil.

The strategy

Weighing the species' traits, the surviving natives and the site's remoteness, the team chose to apply herbicide over multiple consecutive years. The key was coming back every year — through heat, humidity and rough ground — to treat what regrew from rhizomes and the seed bank. After nearly two decades of consistent effort, park staff could begin restoration and replanting.

The same West Beach panne in 2009, choked with common reed (top), and in 2022 after restoration (bottom). NPS.

Mission accomplished

• A healthy panne: native species replace the invasive monoculture, and wildflowers bloom where a wall of grass stood.
• Ongoing care: park staff monitor the panne every year to keep it a high-quality, biodiverse example.
• Fast, by nature's clock: in less than two decades, decades of damage were repaired. Partnerships like this can turn restorations once thought impossible into successes.

Sources

Based on "Great Lakes Invasive Plant Management Team Successfully Restores Intradunal Wetland," Indiana Dunes National Park, National Park Service; a work of the United States government in the public domain.