The Dirt on Acadia

It was a gorgeous morning in late June, and we were in what might be the most idyllic section of Acadia National Park. We stood at the edge of Hemlock Bridge, one of the park’s famous stone archways, listening to the waters of Maple Spring Brook trickle below. A light breeze rustled the canopy of hardwoods and conifers overhead, and sunlight speckled the crushed gravel of the carriage road.

It was a perfect day, but I wasn’t there to enjoy the views. We had work to do. Just behind us, a trail cut 2 miles steeply uphill through forest and boulders and ultimately to the granite summit of Sargent Mountain. The National Park Service wanted to bring thousands of pounds of soil up to the peak to help save the park’s most imperiled ecosystem, and managers had determined that the best way to do it was for us, a group of regular people, to lug the dirt there on our backs.

So instead of enjoying the breeze or taking pictures of the stream, we paced and fretted, wondering how much extra weight we could each carry along with the water and snacks in our daypacks. Nearby, park staff carefully weighed plastic bags of dark soil, each between 5 and 20 pounds, and asked us how much we wanted.

Feeling macho, I opted for 20 pounds and tested the feel of the deadweight in my backpack. Unpleasant. I arranged and rearranged the soil until it was tolerably comfortable, while the 20 or so volunteers went through their own rejiggering process. Once all the clips were clipped and the straps were strapped, it was time to hike.

The goal of the Save Our Summits project is to restore native vegetation atop Acadia’s famous granite peaks. Conditions are tough up there: Glacial scouring and a punishing climatic rotation of wind, ice, fog and sun have historically left the soil on top of the park’s mountains thin and nutrient-poor. Yet patches of mountaintop soil, which resist erosion when sheltered by boulders or squeezed into crevices, host remarkable communities of subalpine plants. More than 100 species of plants grow on Acadia’s peaks, most of them typically found much farther north or on higher mountains.

“The types of plants that grow here don’t really grow anywhere else on the Eastern Seaboard,” said Jesse Wheeler, Acadia’s vegetation biologist, who was hiking with us.

Unfortunately, these stalwart plants have to contend with more than just harsh winters. Humans have added what Wheeler calls “erosion vectors” to the summits, putting increased strain on an already fragile ecosystem. Hiking trails get lost on the open, rocky peaks, and hikers tramp through the plant communities, creating social trails and breaking up the soil with their footsteps. Climate change, too, has caused an uptick in erosion with more rainfall, stronger storms and increasingly fluctuating temperatures.

As far back as the 1990s, Park Service staff knew they had to act to protect their mountaintops, but they weren’t sure how aggressive to be. They piloted a project on Cadillac Mountain in 2000 to test how well soil patches on the park’s most-visited summit would regenerate if hikers were kept out. Park staff roped off certain areas and then monitored them for years to see whether the eroded sections would restore themselves naturally. Fifteen years later, they had their answer: Nature didn’t work quickly enough. “If the soil is gone, it’ll take centuries for it to return, even if people stop hiking up there,” Wheeler said.

Park managers saw they needed to be more proactive if they wanted to ensure the future of this rare ecosystem. The Park Service partnered with local organizations, including the Schoodic Institute, Friends of Acadia and the Native Plant Trust to brainstorm solutions. Ultimately, the group members decided to replenish the soil themselves. Their Save Our Summits project began in 2023, when hikers carried 3,750 pounds of soil to the tops of Penobscot and Sargent mountains. The total was enough to cover 29 individual plots with about an inch of dirt, just enough to give native plants a foothold.

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Getting those plants to grow, however, is another challenge. The Park Service learned from experimentation that pampered greenhouse-grown plugs don’t work, Wheeler said, because they aren’t able to survive the brutal freeze-thaw cycle on the peaks. But researchers found little difference between test plots that had been seeded by biologists and others that were left to reseed on their own. Once all this year’s soil has been carried up Sargent Mountain, the biologists will spread it into the areas they want to reestablish and hold it in place with biodegradable erosion control fabric. They are continuing to test planting methods: This fall, half of the plots will get a mix of fast-growing native plant seeds, while the other half will be left to reseed naturally.

But the most difficult part is still getting the soil up there. The team originally considered using a helicopter to transport the soil but believed it to be too expensive and environmentally disruptive to be a real option. They went instead with volunteers. They piled up mounds of dirt — sourced locally and sterilized to prevent the spread of unwanted plants and microbes — near trailheads and asked park visitors and community members to haul it up one backpack at a time.

Last year, they held only one public event, dubbed a “hike-a-thon,” which brought almost 100 volunteers into the park on a single, hectic day of soil hauling. Park employees, school groups and some others also transported soil that summer, and leaders ultimately decided those smaller, semi-regular efforts were easier to manage. With that in mind, the project hosted weekly public soil hikes between June and September this year.

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Ours was the first hike of the season, and we started together single-file up through the forest. It was tough going from the start: The trail was steeper than I expected, and we had to pick our way carefully over roots and rocks. I was already starting to regret my 20-pound choice, which seemed to get heavier by the step. I chatted with my neighbor to keep my mind off the strain.

John Baird, a regular trail-work volunteer with Friends of Acadia, told me he’s trying to be a more conscientious hiker. “Lots of hikers aren’t really aware of how harmful it can be to walk off of the rock surfaces at the summits,” he said. He’d noticed the increasing amount of erosion on the mountains and was excited to help remedy the problem. “Plus,” he said, “I’ve accidentally carried enough soil out on my shoes over the years that it’s about time I put some back.”

The forest thinned as we continued uphill, depriving us of shade. The rocks were larger here, and we worked hard to find footholds and pull ourselves up and along the trail. We were all breathing pretty heavily by then, and my back was aching, but we kept on.

Acadia’s mountaintop geology revealed itself as we climbed. We eventually emerged onto the lower ridge, a broad gray whaleback rolling toward the summit. The stone expanse was dotted with small islands of vegetation — examples of the very habitat we were working to restore. Wheeler and the other biologists pointed out various rare native plants, including three-toothed cinquefoil and poverty oat grass, which are both on the list of plants they hope to reestablish.

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And then: After a final push, we made it. The volunteers eagerly removed the soil bags from their backpacks and handed them over (some after taking a quick dirt-sack selfie first). The biologists collected the cargo, a total of 265 pounds of dirt among us, and piled up the bags to await spreading in the fall. The hope was to have 4,000 pounds of new soil on top of Sargent and Penobscot mountains by the end of September — a goal I later confirmed they exceeded by several hundred pounds — and eventually, to expand the effort to other parts of the park, and even to other parts of the National Park System. But those were jobs for other volunteer pack animals. For the day, our work was finished, and there was nothing left to do but eat lunch and take in the view.

Our packs unburdened and our good deed done, we practically floated downhill.