Scottish Pinewoods Study Reveals Vulnerability of Ancient Forest

Scotland's unique Caledonian pinewoods stretch back in time to the last Ice Age. These majestic woodlands survive in fragments across the country, hosting a wide range of wildlife and creating a very special environment.

Once covering much of the Scottish Highlands, this forest is a huge part of Scotland's culture but has now diminished to small pockets of habitat over 42,000 acres in total—an area just 2% of its original size.

Now, a new study—the first such study into this globally significant ancient woodland in 60 years—has revealed that these pinewoods are "on a knife-edge" and that bold action is required to save them from being lost forever.

Over the past four years, Trees for Life, partnering with Forestry and Land Scotland, NatureScot, Scottish Forestry, Scottish Land & Estates, and Woodland Trust Scotland, assessed the state of 72 of the remaining 84 fragments, which are scattered across the Highlands from Loch Lomond, northwards to near Ullapool, and eastwards to Glen Ferrick near Aberdeen.

In one of the most comprehensive surveys of the pinewoods ever undertaken, the team carried out detailed studies of more than 1,200 half-acre plots in total across the sites.

Scotland’s national tree, the Scots pine, was found to be in serious decline at a quarter of the plots.

Threats to Scottish Pinewoods

The analysis brought to light the main threats to the precious Caledonian forest. The first of these is high deer numbers—with deer preventing young tree growth and regeneration. Deer eat pine saplings, strip important vegetation, and lead to some pinewoods being replaced by birch. High deer populations are one of the main barriers to the recovery of the habitat.

Herbivore impacts, primarily from deer, were determined as high or greater in 63% of Caledonian pinewood. Caledonian pinewood plots could have at least twice as many tree species regenerate successfully if not for over-browsing, and selective over-browsing suppresses more tree diversity overall than blanket over-browsing. Tree species most severely impacted by over-browsing are especially important for leafy lichens, pollinators, and berry-feeding animals.

The study found that despite efforts made in the 1990s to protect pinewoods with deer fencing, this was not particularly effective. Often, fencing protected only small areas, and deer could frequently get through or breach fences before they had the 30 years required for successful establishment.

The spread of non-native conifers is another major threat to these native ecosystems. Non-native conifers, originally planted in the 1950s, are still present in a third of the plots. The main culprit is Sitka spruce, which crowd and slowly kill Scots pine—a risk that increases year-on-year, with mature conifers an acute threat to Scots pine and other native trees. Non-native trees, primarily Sitka spruce, were recorded in 32% of Caledonian pinewood and considered abundant in 7%.

Lack of long-term management for protected areas and the emerging impacts of climate breakdown are also key factors in these pinewoods' vulnerability.

The is fact that remaining pinewood areas are often small in size—only 11% of the remaining sites are over 500 hectares in area. Isolation reduces biodiversity and therefore reduces resilience in the face of our warming climate.

“In the worst cases, the pinewoods have suffered non-native conifer planting or fire followed by grazing pressure, with the impacts of climate breakdown a growing threat,” said Trees for Life’s Senior Ecologist James Rainey, who led the study.

23% of remaining Caledonian pinewood is now critically threatened and will be lost without urgent action.

The few areas that are doing well are those that are benefitting from landscape-scale action, including the reduction of deer pressure and the removal of non-native conifers.

Protecting Scotland's Ancient Forest

The study’s findings will be used by Trees for Life to develop a follow-up project with landowners and land managers for practical action to protect, expand, and reconnect the most threatened pinewoods. Additional conservation is already underway at 12 sites.

Caledonian pinewoods are best recovered through natural regeneration and expansion and help maintain genetic diversity, distinctiveness, and structural variability that contribute to the trees' health, resilience, and character.

As James Rainy stated: “These pinewoods should be playing a key role in Scotland’s fight-back against the climate and nature emergencies, but right now most are on their last legs. It’s not too late to turn this around, but that means seriously stepping-up restoration and rewilding action.”

To learn more and download the full report, visit Trees for Life.