Climate Change


Weather takes place over minutes, hours, or days; changes in climate are measured over decades, centuries or millenia. The rapid pace of environmental change since industrialzation is threatening what we love most about Acadia. With change inevitably comes loss. Park managers use science-based management approaches to determine what change to resist, what change to direct, and what change to simply accept. In the face of rapid environmental change, what do we stand to lose and what can you do to help?

Acadia's Changing Climate

Acadia's climate has always changed. Melting glaciers, rising seas, forest fires, shifting plant and animal populations, and other changes have been occurring in Acadia for thousands of years. Ancestors of the Native American Wabanaki people lived through and adapted to these changes. They transferred knowledge across generations that sustains their cultural and community connections to the place we now call Acadia, which substantially contribute to our understanding of this place. This change accelerated in the last few centuries as European settlers cleared forests, filled wetlands, built roads and other infrastructure, and as the owners of local and distant industries polluted the air, land, and water

But now, Acadia National Park is a measurably different place than it was at its founding just over 100 years ago. While its beauty endures, its forests, lakes and coasts are being altered by people through land uses, pollution, tourism, invasive species, and climate change. Acadia is seeing longer growing seasons and fewer species that we know and love. Less biodiversity, more invasive species, and extreme weather events are damaging landscapes, cultural resources, and infrastructure.

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Acadia National Park is measurably different than it was at its founding more than 105 years ago. What threats are there to Acadia and how is the park responding.

map of the east coast showing red where ocean waters are warming
In August 2018, scientists using satellite data and sea-based sensors measured the second warmest sea surface temperatures ever observed in the Gulf of Maine. Shades of red and blue indicate how much water temperatures were above or below the long-term average for the region.

NASA Earth Observatory images by Lauren Dauphin, and sea surface temperature data from Coral Reef Watch

Climate Change Impacts

Changing Waters

  • Rising Ocean Temperatures: The normally cool Gulf of Maine, which surrounds Acadia National Park, has risen approximately 3°F over the last century. On the surface, this may seem like a small difference, but it means the Gulf of Maine is warming rapidly and is expected to warm much faster than most of the world’s oceans. The Gulf of Maine is one of the fastest warming areas of the global ocean. Frequent marine “heat waves” are changing how animals feed and migrate and altering tide pool communities.
  • Sea Levels are Rising: Sea levels have risen by eight inches since 1950, and growing seasons have lengthened by more than two weeks. Shorelines are eroding, including Wabanaki heritage sites.
  • The Ocean is More Acidic: Since the industrial revolution began, the acidity of the ocean has increased by 30%, a faster change than any known change in ocean chemistry in the last 50 million years. More acidic oceans make it difficult for ocean, like clams and snails, to form and maintain shells.

Changing Landscapes

  • Rising Temperatures on Land: The annual average temperature at Acadia has risen 3.4°F over the last century. The warming we expect by the end of the century is approximately ~5-13°F; It took only 8°F to transition from the glacial maximum 20,000 years ago (when Acadia was covered by a mile of ice) and the beginning of the century.
  • Increase of Pests and Diesease: Acadia’s visitors are now becoming accustomed to the health risks represented by Lyme and other diseases carried by ticks, with warming implicated in the increase in ticks and these diseases throughout coastal and southern Maine.
  • Longer Growing Seasons: Maine has been experiencing earlier springs, later falls, and much longer growing seasons.
  • Native Plant Decline: One of every six plant species found on MDI when Acadia was founded no longer occurs on the island, and many more native plant species have declined in abundance.
  • Increasing Spread of Non-Native Plants: Non-native plants have become more common and are crowding out native trees, wildlife, and plants.
  • Increasing Plant Drought and Heat Stress: Acadia is mostly forest, and cold-climate red spruce makes up 40% of the forest in Acadia. Red spruce is at risk from summer drought and winter warming and is predicted to lose suitable habitat.
  • Increasing Forest Pests and Diseases: Introduced insect pests threaten trees in park. The Red Pine Scale insect killed all the red pines throughout the park in just a few years. Others, such as Emerald Ash Borer and Hemlock Woolly Adelgid, are expected to spread to Acadia in the near future.

Changing Skies

  • Bird Populations Under Stress: There are fewer birds now than there were 50 years ago, and populations of some birds are shifting. Some species, like boreal chickadees, no longer breed in Acadia, and others have newly arrived to breed here. Recent studies have shown bird populations have dropped nearly 30% in North America since 1970, almost 3 billion birds. This includes common species dramatically declining at Acadia too, NPS data has shown significant declines in the last 15 years.
  • More Rain: Acadia is now seeing six inches more precipitation each year on average. Warmer and wetter springs and winter are changing Acadia's plants, animal feeding patterns, and visitation patters.
  • More Intense Storms: Acadia is experiencng bigger storms, more rain, and less snow. Mountain summits, carriage roads, and trails have been eroded, washed out, and flooded by these new storms. Strong winter storms in New England, called Nor'easters, are causing heavy damage to Acadia's coastline and operations.
A June 2021 storm dropped a record-breaking 5+ inches of rain in less than 3 hours and damaged Acadia's 45-mile historic carriage road system, as well as trails, streams, and paved roads. The storm caused over $1.5M in infrastructure damage and repair costs, not including the environmental costs.

Why Is This Rapid Change Happening?

Like a sleeping bag on a cold night, natural greenhouse gases perform the essential function of trapping enough heat in the atmosphere to support life on Earth. However, fossil fuel burning, deforestation, large-scale live-stock farming, and other human activities have produced historically high levels of carbon dioxide, methane, and other greenhouse gases in the atmosphere—carbon dioxide levels today are at their highest in three million years. While Earth does go through natural warming and cooling cycles lasting tens of thousands of years, the vast majority of scientists agree that recent changes in Earth’s climate are caused by human-produced greenhouse gases that trap heat close to the planet’s surface.

What Do We Stand To Lose?

Acadia has already seen the loss of some of its major species, without a significant reduction in greenhouse emissions, there is a chance that some of these fragile pieces could be lost forever:

  • Native Animals- Native species in the Gulf of Maine have adapted over long periods of time to thrive within a certain temperature range. When the temperature increases, the environmental conditions to which they are adapted are suddenly gone and for many species, warmer waters are completely inhospitable.

  • Native Plant Communities- Acadia’s plant communities have already changed dramatically, with one in five of the species documented a century ago by the Champlain Society no longer found in the park. While our forests are likely to adapt over time with a new mix of species, the transitions can be disruptive. Trees under stress may be killed more easily by pests and pathogens, including invasive species. A recent example is the widespread and unexpected death of many of Acadia’s red pines.

  • Recreation Opportunities- in the Northeast of the United States, winters are projected to warm three times faster than summers resulting in less snow coverage and fewer temperatures below freezing. This means fewer days of ice skating, snow shoeing, cross country skiing and other cherished winter activities in Acadia.
  • Thunder Hole- Carved naturally out of the coastal rocks, waves have been battering this tiny inlet for centuries. There is a small cavern at the bottom of the inlet and the combination of the waves hitting the rocks and the release of air from the cavern cause a thunderous boom to happen. Often, visitors say a trip to Acadia is not complete without a visit to Thunder Hole. If global warming and sea level rise continues unabated, it is very likely Thunder Hole will be covered and other portions of Maine's coastline will be forever changed.
  • Coastal Buffer Zones- Rising sea levels put the very existence of the marshes in the park such as Pretty Marsh, Bass Harbor Marsh, and Northeast Creek at risk. Marshes like act as natural water filters and provide a habitat for fish and birds and other wildlife; they are nursery grounds for fish species and they serve as buffers between the ocean and the upland area, mitigating wave and wind impact during storms. Most importantly, marshes absorb carbon dioxide from the atmosphere, something they do better than any other type of habitat.

  • Lobster- Significant species migration due to climate change is already occurring in the Gulf of Maine. As the Gulf continues to warm, there is a possibility that the lobsters could eventually migrate beyond the reach of Maine’s lobstermen and women.

Thunder hole on a stormy day
Thunder hole on a stormy day

NPS photo by Kent Miller

What's Next?

Without a major reduction in these global greenhouse gas emissions, scientists project increasing changes in Acadia’s climate over the next century. These types of changes are likely to continue and even accelerate, with dramatic impacts on the park.

  • Faster warming: In the next 50-60 years, average summer and winter temperatures in Maine are projected to increase by over 5°F (2.8°C) relative to pre-industrial levels.

  • Extreme weather: More intense storms threaten and associated heavy rainfall have caused damage to some historic trails, carriage roads, hiking trails, and even park motor roads

Still other changes are driven by complex interactions between climate and fire management practices, natural drought, animal behavior, invasive species, and human use of the park. By studying the shifts we are already seeing in Acadia, we can better understand the meaning of conservation in a time of change.

A New (RAD) Approach

Park managers traditionally sought to preserve parks based on historic conditions. To restore things to the way they were. Now, managers must consider both the changes that have already occurred and future changes expected in the coming years and decades. The focus has shifted from “restoration” to a previous state to actively managing for future health.

This new management approach— called RAD for short—requires choosing when and where to

  • Resist environmental change—meaning to preserve habitats and cultural resources as they currently exist at all costs;
  • Accept change, by allowing plant and animal populations to expand, contract, or shift and by accommodating the impacts of changing weather and storms on infrastructure and cultural sites; or
  • Direct change by adapting habitats and species and infrastructure through anticipated radical change.

This new flexible framework allows us to be forward thinking and fiscally responsible, proactive instead of reactive, and provides us with the best chance to save what we love and value about Acadia.


Leading the Way

Together with our partners in science at the Friends of Acadia and Schoodic Institute, Acadia National Park is leading the way by studying and applying this framework in three key pilot projects:

  1. Great Meadow Wetland near Sieur de Monts Spring and visible from the Park Loop Road is a familiar spot to many visitors. We’re replacing an undersized culvert with a bridge to improve water flow and reduce flooding. Adding the bridge accepts and adapts to the heavier rain events driven by climate change.

  1. Cadillac Summit, one of the most popular and iconic spots in the park, lost plants and soil to trampling and erosion. Park managers are evaluating how to restore plants and soil given the rapidly changing climate on the summit and increases in visitation. Scientist are experimenting with planting new native species and restoring soils that are more resilient to future conditions. This is an example of how to direct change toward desired future conditions.

  1. In Bass Harbor Marsh, we’re focused on removal of invasive plants that have crowded out native plants and wildlife—an example of resisting an undesired change

Through these and other scientific studies we're discovering the ways that Acadia's summit can provide refuge to threatened species during climate change and Acadia science can help other land managers manage for changes and impacts in the future. Other climate studies include:

  • Scientists are studying how strong winter storms known as Nor'easters are damaging the coast of Acadia National Park as well as other national parks in New England.
  • Studying sediments in ice cores in Acadia's lakes and ponds.
a researcher stands at a table surrounded by green plants, rocks in the background
Science at the Summit

Learn about the ways climate change is challenging researchers to rethink how they manage Acadia's fragile mountain summits.

blue sky reflects in standing water below green hills
Great Meadow Wetland

Learn about this expansive wetland ecosystem and the steps scientists are taking to restore its health in the face of change.

sunset reflected in water amongst wetland grasses
Bass Harbor Marsh

Learn more about beautiful Bass Harbor Marsh and efforts by researchers and volunteers to stem the tide of invasive species.

Two visitors watching the sunset from the top of a mountain
Two visitors watching sunset from the top of Cadillac Mountain

NPS Photo/Victoria Stauffenberg

How You Can Help

You are a part of this equation, too. Visits to Acadia—now up to an estimated 4 million per year—are strongly influenced by weather, and therefore, over the long-term, the changing climate. The park now experiences a longer busy season. With a workforce composed largely of seasonal employees, it is difficult for the park to adjust to the longer season. The increase in visitation is contributing to crowding, sometimes unsafe conditions, and damage to natural resources at favorite destinations such as Cadillac Mountain. The park worked with its partners and the surrounding community to create a transportation plan in hopes of resolving some of these challenges and continuing to provide high-quality experiences for visitors.

Whether it's helping out with citizen science while hiking a trail, choosing a bike over a car to explore the park, or reducing your carbon footprint of your house... check out what you can do while you're here and at home to continue caring for Acadia National Park and green spaces everywhere. Visit our Get Involved page to learn more and visit the National Park Service Climate Change page to learn more about what parks are doing across the country to combat climate change.

Visit our partners at Friends of Acadia and Schoodic Institute to learn more about how you can help protect Acadia for future generations.


More About Climate Change at Acadia

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    Last updated: May 10, 2024

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