Clearing Glossy Buckthorn from Acadia's Great Meadow

Mention Acadia National Park and most people think of mountains, coast, forest and lakes. Wetlands rarely make the postcard, yet they cover 20% of the park — and they are among the most biodiverse ecosystems on Earth.

Why wetlands are worth the work

• They clean water. Wetland plants slow moving water so that sediment, nutrients and pollutants settle out.
• They absorb floods and droughts. One acre of wetland can hold more than a million gallons of water.
• They store carbon. Wetlands cover only 5% of the Earth's surface, but the partly decayed plant matter in their soils holds 25% of the carbon in the world's soil.
• They shelter rare life. Acadia's wetlands support most of the park's rare plants — species that have vanished from other parts of Maine.

Those benefits come largely from native plant communities adapted to local conditions over thousands or millions of years. For a long time, though, wetlands were treated as wasteland: many of Acadia's were dredged, ditched or filled before the park existed, and roads and development still send runoff into them and choke their flow. When habitat is broken up, water and air are polluted, and soil is compacted, native plants struggle — and invasive species, brought in by people to places where no pests or predators hold them in check, flourish.

Image from the National Park Service's page.

The crew and its main target

Acadia began managing invasive species in 1989, when purple loosestrife started threatening its wetlands. Twenty years later the park set up a dedicated invasive plant program. Each year a team of seasonal National Park Service employees finds, removes and studies invasive plants across the park. In 2022 the four-person crew searched almost 1,000 acres for 25 target species — and one of them, glossy buckthorn (Frangula alnus), took more time, more ground and more treatments than all the others put together.

The Great Meadow is one of more than 150 sites the team returns to year after year. When the work there began, thick stands of mature buckthorn had been dropping fruit for a long time. The seeds stay alive in the soil for several years, and even first-year shoots from that seed bank can bear fruit, so clearing the big shrubs once is never enough.

Image from the National Park Service's page.

Many tools at once

The crew uses integrated pest management — several methods in combination:

• Cutting mature shrubs with hand saws and pruners. Cutting alone makes buckthorn grow back, so each stump is then treated with herbicide or covered with a black bag.
• Hand-pulling seedlings once the tall shrubs are gone. It suits a large group of volunteers, but for a small crew it is slow, it disturbs the soil, and it can leave pieces that resprout.
• Spraying seedlings' leaves with herbicide, after weighing the site, the season and the weather to limit harm to native plants and other resources.

Removal is only part of the job. The team surveys wide areas for new infestations, rechecks study plots every year, and records the location and estimated size of every plant it treats, along with the area searched on each visit.

The results

Those records show the payoff. In the Great Meadow, the buckthorn the crew treated in 2016 would have covered .54 acres (about 23,000 square feet). In 2022, searching a similar area, it found only .05 acres (2,200 square feet). That drop is what made the 2023 goal realistic: surveying and treating all 116 acres of the Great Meadow, part of the Wild Acadia project and the wider effort to restore the meadow.

Invasive plants will never be wiped out; they are part of a world people have changed. The real aim is to bring back native plant communities, because when they are pushed out of a wetland, its water filtering, soil building and wildlife habitat decline with them. As wetlands disappear worldwide and the climate changes, healthy ones are both more vulnerable and more valuable than ever.

Sources

• National Park Service, Acadia National Park: "Removing Invasive Plants from the Great Meadow."