Outside of Baxter State Park, John Hagan trudges through debris from a recent timber cut. At the crest of a steep bank the woods thicken, hiding stumps from logging 30 years ago.
"A lot of what we end up doing is being forest detectives, trying to reconstruct what happened here," he said.
He's looking for tell tale markers of much older woods. That means a lot more naturally fallen logs and a lot fewer signs of human disturbance.
Descending to a stream bed, Hagan consults a map on his tablet computer. It displays the forest in vivid color. Greens and yellows mark logging areas. Dark blues and magentas show the much older, taller trees Hagan's headed towards.
"It's kind of like a CAT scan for the forest," he said.
Maine is the most heavily forested state in the country. But after generations of logging just a few stands of valuable old growth trees remain across its vast north woods.
Now, for the first time, airborne imaging data allows researchers to find those old trees with incredible precision.
Hagan’s nonprofit, Our Climate Common, used light detection and ranging, or LiDAR, elevation data collected from flights over Maine. That mapped out old forest across 10.3 million acres in Maine’s unincorporated townships. Almost all that land is privately owned and logged repeatedly. The method, which maps the height of trees, is 94% accurate, according to Hagan.
"So now we've got a map. We know where it is. We know who owns it. We know how fast we're losing it. So now we're pivoting to OK, how are we going to conserve it?" Hagan said.
Just 3% of the north woods can be considered late successional or old growth forest, according to Our Climate Common's research. The tool isn't perfect. For example, it didn't map out wetland forests that could contain old trees that aren't very tall.
But it's still a way to reveal secret pockets of untouched forest.
Descending down the wooded bank, the landscape transforms. Generously spaced spruce, hemlock and white pine tower above. Moldering trunks lay under a blanket of saplings gently swaying in the wind.
It’s a rare glimpse of what Maine’s forest looked like before Europeans showed up.
"You know, 300 years ago or so, probably 70% to 80% of Maine's Forest was in a what we would call a late succession, or old growth condition, probably 150, 200, 300 year old forest," Hagan said. "That's just what it did before we came along and figured out so many things to use wood for."
Old growth forest are critical to biodiversity. Fallen trees provide unique habitat. And some species of beetles, lichen and fungi need aged trees to survive.
Hagan had a mission for this patch of woods. Based on his LiDAR mapping, it might hold the tallest white pine on record in the state.
Following the map, he navigates directly to a tiny black spot on the screen. In real life, it’s a huge white pine surrounded by similarly gigantic trees. And after some calculations, Hagan confirms — at 155 feet, roughly 14 stories, it's likely the tallest in Maine.
And no one was going to find it without this technology, he said.
"Imagine crisscrossing Maine looking for the tallest tree when you got nothing to go on," Hagan said. "So we had LiDAR, and as you saw, we walked right up to the tree in the middle of nowhere, and it was right where it's supposed to be."
The mapping project comes amid increasing focus on the value of old forests for ecological balance and as a tool to store climate-warming carbon dioxide pollution.
Outside of state-owned lands, northern Maine's old forest is disappearing. Hagan’s research predicts losing half of the 148,000 acres that remain on commercial timberlands in two decades. That's an area not quite as big as Baxter State Park.
Ecologist Janet McMahon, who helped with the study, said a lot of managed forest is harvested every 40 to 60 years. So when old trees are gone, there might not be anything growing to replace them.
"A forest can never grow to be a forest anymore. It can produce timber, obviously, but there's not much of an overstory left anymore," McMahon said.
Old trees store three to five times as much greenhouse gas emissions as younger ones. So preserving them is critical to curbing climate warming pollution, said Jon Leibowitz, CEO of the Northeast Wilderness Trust.
"Old forests store immense amount of carbon, and if they get harvested or logged, you lose that carbon in various ways, so ensuring that these remaining old forest stands remain standing is really essential," he said.
The trust works to conserve land from any logging and development. Leibowitz thinks widespread LiDAR mapping could be a game changer for acquiring and protecting parcels across New England.
"While our area is divided by political lines, it's one large ecosystem and connectivity is absolutely essential," he added.
There’s an ongoing debate about how much old forest should be conserved, according to the Maine Forest Products Council trade group. Major landowners including The Weyerhaeuser Co. and JD Irving Woodlands are council board members. They also approved funding for the mapping project, said director Patrick Strauch.
"It's not an us versus them relationship," he said.
Even in small patches, old forests are beneficial to wildlife and the entire landscape, Strauch said. Mapping could open the door to new targeted easements or other forms of protection. But maintaining those stands will have a cost.
"The trouble is, if it's large timber up to a certain point, it has even more value. So they become more expensive," Strauch said.
Conservationists suggest that old trees might now be worth more left alive. Landowners could get the same or better returns by selling their value as carbon credits to offset greenhouse gas emissions.
Andy Cutko, Maine Bureau of Parks and Lands director, isn't so sure. State lands, including Baxter park and ecological preserves hold about 107,200 acres of old forest. Some of that is protected, but public land parcels outside of state parks depend on timber harvesting for revenue.
And shifting to carbon storage presents unknowns, Cutko said. Does a carbon offset allow for more pollution? And will it just wind up leading to cutting more trees somewhere else?
"Those are some pretty heavy questions," Cutko said. "So we're not diving headlong into carbon markets just yet."
Back in the woods, Hagan took a moment to marvel at his surroundings. Pale November sunlight graces tree crowns. The forest was quiet, except for a rushing stream and a breeze through the limbs.
"I'm not that comfortable with the word spiritual, but many people are fine with it, and they would look at the stand like this and be spiritually moved," Hagan said.
Maine Public’s Climate Desk is made possible by Androscoggin bank, with additional support from Evergreen Home Performance, Bigelow Laboratory, & Lee Auto Malls.
