Study Explains How Acadia National Park Found Success Managing Invasive Plants

According to a 2025 study (attached), Acadia National Park has had tremendous success in their efforts to control invasive plants over the past three decades. The park has less than 1 percent cover of invasive plants, a big accomplishment considering how difficult invasive plants can be to eradicate.

Invasive plants cause plenty headaches for national parks across the country. According to the National Park Service, the spread of invasive species is a major factor contributing to undesirable landscape level change and ecosystem instability in national parks. As of 2022, there were over 2.6 million acres of national park units infested with invasive plants, of which only approximately 57,000 acres are controlled, in which invasive plant infestations have been reduced to a level that can be maintained by park staff.

A study of 39 national parks in the northeastern US from 2007 to 2018 found that 92 percent of the parks had invasive plant species present in more than half of the study plots, and 80 percent of the parks were experiencing increases in abundance of at least one invasive plant species.

This makes Acadia’s success all the more impressive.

The current study, led by research from the Schoodic Institute, points out that part of Acadia’s management success is due to the park’s relative isolation, northern location, and coastal influence, where a cooler climate and rural landscape have meant fewer introductions. However, Acadia's ambitious 35-year effort to inventory and manage select invasive plants within the park's boundaries has also played a key role.

The land that is now Acadia National Park is a part of the homeland of the Wabanaki Nations. Between the 1500s and 1800s, Wabanaki people were displaced, and most of the land that is now in the park was privately owned and managed as homesteads, gardens, woodlots, and pastures. Many of these parcels had been planted with invasive plants prior to NPS involvement.

Acadia was established in 1916, with new parcels having been added since then. After transferring to federal protection, most areas have reverted to forest. These characteristics make parklands especially vulnerable to the impacts of invasive plants, notes the study.

“Following a field survey of nonnative flora in 1986, NPS natural resource staff identified 12 of the ~ 289 non-native plant species on the park's flora inventory as species of management concern based on the best available science,” says the study. “Of these, purple loosestrife (Lythrum salicaria) was identified as the most threatening to Acadia's resources based on the impact of the species in other protected areas.”

The plan that was established in response included management goals, action thresholds, quantitative monitoring methods, and management actions including prevention and early detection, education, and herbicide treatments. In 1996, subject experts confirmed that efforts had achieved NPS goals of preventing invasion of wetlands that had been free of purple loosestrife, and that extant populations of purple loosestrife were being managed below ecological impact thresholds, according to the study.

Resource managers at Acadia then started to target other invasive plant species in the early 2000s, as funding and staff allowed. Expanded invasive plant management required a seasonal crew of 3–6 people, as well as high quality inventory and monitoring data that identified the extent of the threat and past program successes.

Support from park partner organizations, such as Friends of Acadia, played a crucial role in the expansion of the program, as a lack of base funding from the park for invasive species management would have otherwise limited the efforts.

As the researchers point out, as a result of a partnership that provided multi-year funding in 2009, Acadia staff launched an intensive campaign to: (1) control and reduce the extent of cover and abundance of select invasive species, (2) reduce the sources of these species, and (3) detect new occurrences of these species early during their establishment (early detection/rapid response) following established methods.

As a result, invasive plant cover was reduced to less than 1 percent, and by 2011, park staff was managing 20 invasive species.

Since finding success in their management efforts, management teams have shifted from time-consuming initial treatments to surveying for new infestations and working to maintain low densities at management sites.

Unfortunately, Acadia’s success story hasn’t been replicated in other protected areas in the Northeast. The researchers point out that this is due to insufficient staff and financial resources, competing priorities, higher levels of plant invasions, and factors such as overabundant deer or non-native earthworms that enhance plant invasions.

Acadia’s successful management of invasive plants demonstrates that long-term investment, high-quality evidence, clear, achievable goals, and strong partnerships are key factors for success. The study points out that these factors will be even more critical as climate change threatens parks across the United States and makes it potentially more difficult to control invasive plants.

“Responding to these changes requires articulating desired but realistic future conditions for resources in protected areas, then acting (e.g. invasive plant removal, native plant revegetation) to achieve these goals,” write the researchers. “Therefore, continuous management through a flexible experimental approach will be critical to successful invasive plant management in the future.”