A Cambridge-led research team has transformed laser scans collected from a light aircraft into detailed three-dimensional maps of Scotland's Cairngorms National Park, and the resulting images capture something rarely documented at this scale: native woodland creeping back across ground where trees have been absent for centuries.
The survey covered 569 square kilometers (km²) of the national park and identified more than 6 million individual trees, recording the exact height of each one. Some 2.65 million of those trees — just over 40 percent of the total — stand less than 5 meters (16 feet) tall, marking them as young, naturally regenerating specimens rather than remnants of older forest.
The work documents an early success story for the Cairngorms Connect nature restoration partnership, whose landscape-scale approach to deer management spans 60,000 hectares. According to the team, millions of young trees have established naturally following an increase in deer culling across the partnership area.
How the Cairngorms survey was carried out
The raw data came from LiDAR, a laser-scanning technology that measures distance by timing how long pulses of light take to bounce back from whatever they strike. The equipment was mounted in a light aircraft that flew 600 meters (about 2,000 feet) above the ground, sweeping over a huge swath of the park and building up a dense cloud of measurement points below.
Turning that point cloud into a tree-by-tree inventory required a new analytical approach. The Cambridge team developed an AI-supported method for processing the scans, which allowed them to distinguish individual trees from surrounding vegetation and terrain across the entire survey area — a task that would be impractical to attempt manually at this resolution and scale.
To check that the automated results were trustworthy, the researchers took point measurements on the ground and compared them with what the maps showed. Those field checks validated the accuracy of the mapped trees, giving the team confidence that the digital inventory reflects what is actually growing in the park.
What the maps show
The resulting images are unusual in their level of detail. Rather than depicting woodland as a generalized green patch, they resolve each tree and its height, making it possible to see where regeneration is concentrated and where it is only just beginning.
- More than 6 million individual trees identified across the 569 km² survey area.
- Every tree measured for height, not merely counted.
- 2.65 million trees — a little over 40 percent — under 5 meters tall, indicating recent natural regeneration.
- Ground-based point measurements used to validate the accuracy of the mapped results.
Regeneration clusters at the forest edge — and beyond
The small, regenerating trees are found mostly near the edges of existing forests, which is where seeds are most likely to land. That pattern is what ecologists would expect from natural seed dispersal, and it suggests the new growth is radiating outward from established woodland rather than appearing at random across the landscape.
But the maps also revealed a more surprising detail: some new trees had established more than half a kilometer from the nearest forest edge. Those outliers point to how far seeds can travel, and they hint at the potential for woodland to spread into open ground well beyond the current tree line.
Habitat type shapes where trees take hold
Not every patch of ground proved equally receptive. The survey found that fewer new trees had established in boggy areas than on dry heathlands, indicating that local habitat conditions play a meaningful role in determining where regeneration succeeds. That distinction matters for anyone trying to predict how quickly a landscape will recover, because it means restoration progress will not be uniform across a park of this size.
Deer management at landscape scale
The recovery documented in the maps did not happen on its own. It followed a coordinated approach to deer management across the Cairngorms Connect partnership's 60,000 hectares, an area far larger than a single estate or reserve. The increase in deer culling is associated with the natural establishment of millions of young trees now visible in the LiDAR data.
That landscape-scale framing is central to the result. Because the partnership operates across a contiguous sweep of the national park rather than isolated fragments, seedlings that germinate in one area have room to spread into neighboring ground. The maps offer a tree-level view of what that approach has produced so far.
A new tool for monitoring nature restoration
Beyond the specific findings in the Cairngorms, the project demonstrates a monitoring method that could be applied to restoration efforts elsewhere. Dr. Aland Chan of the University of Cambridge described the precision and scale of the mapping as a breakthrough.
"The ability to map regenerating trees so precisely, at such a huge scale, is a breakthrough for monitoring nature restoration at a landscape scale," Chan said. "It means we can effectively map young trees, assess whether restoration targets are being met, and inform future restoration work."
That capability addresses a long-standing problem for large restoration programs. Counting young trees by hand across hundreds of square kilometers is not feasible, and satellite imagery often struggles to pick out small individuals beneath or beside taller vegetation. Airborne LiDAR combined with automated analysis offers a middle path: wide coverage with enough resolution to isolate individual saplings and record how tall they have grown.
Repeated surveys could turn those snapshots into a moving picture, allowing land managers to track whether regeneration is accelerating, stalling, or shifting into new habitat types over time. The height data is particularly useful in that context, since a growing cohort of trees would show up as a rising distribution of measurements from one survey to the next.
What the Cairngorms result means
The headline number — more than 6 million trees — is striking on its own, but the more consequential finding may be the pattern behind it. Regeneration is happening naturally, at scale, and mostly in places where conditions are right: near seed sources, on well-drained heathland, and within a management area large enough to give young woodland room to expand.
The Cairngorms maps do not represent a finished forest. They show the beginnings of recovery, concentrated in young trees that will take decades to mature into closed woodland. Yet they provide something restoration partnerships have often lacked: a precise, verifiable baseline showing that a landscape-scale intervention is producing measurable results on the ground.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
