Why removing sheep off Scotland's uplands could hinder climate goals -

For years, removing sheep from Britain’s uplands has been viewed as a simple way to lock up carbon, restore nature and help meet net-zero targets.

But new research suggests that, at least in Scotland’s grasslands, taking livestock off the hill entirely could have the opposite effect where it matters most.

A major study spanning the length of the UK — from Dartmoor to Aberdeenshire — has found that excluding grazing animals can reduce the most stable and climate-resilient form of soil carbon, raising questions about one of the Britain’s widely adopted, and often viewed as progressive, land management policies.

Read more: Beloved feral goats on Langholm Moor nature reserve to be culled by rewilding company

The findings are detailed in the paper ‘Grazer exclusion is associated with higher fast-cycling carbon pools but lower slow-cycling mineral-associated carbon across grasslands’, published in PNAS. | Katharine Hay

The research, led by the University of Manchester and published in the Proceedings of the National Academy of Sciences, examined 12 upland grassland sites across an 800-kilometre south–north gradient, including Glensaugh in Aberdeenshire.

Read more: Wildlife photographer Hamza Yassin campaigns to bring back shop and petrol station to a village he calls home

At each location, scientists compared land that had been ungrazed for more than a decade with neighbouring areas that continued to support sheep or other livestock.

Their conclusions showed that while ungrazed land often stores more visible carbon in plants and plant litter — the layer of dead organic material that accumulates on top of the soil surface — it can lose a more stable and far more important form of carbon hidden underground.

Read more: Ministers set to double organic land in Scotland ahead of Holyrood election

This long-lived carbon, known as mineral-associated organic carbon (MAOC), is bound to soil minerals and can remain locked away for centuries. It is this “slow-cycling” carbon that offers genuine long-term protection against climate change, and it appears to decline when grazing is removed altogether, the authors said.

“Grasslands store around a third of the world’s terrestrial carbon, most of it in soils,” said Dr Luhong Zhou, the study’s lead author. “But not all carbon is equal. Our results show that total grazer exclusion does not necessarily increase the forms of soil carbon that are most resistant to warming.”

The findings are particularly relevant for Scotland, where vast tracts of upland grassland are central to government-backed rewilding, peatland restoration and agricultural transition schemes, where removing sheep is often framed as an unambiguous environmental good.

The authors emphasise that their findings do not argue against reducing overgrazing. Rather, they call for more balanced grassland management approaches that account for both total carbon stocks and carbon persistence. | Katharine Hay

The researchers stress that they are not advocating a return to overgrazing, which can damage soils, hinder growth and impact biodiversity. Instead, they argue for balanced management that reflects the complexity of upland ecosystems.

In Scotland’s uplands, the removal of grazing animals tends to trigger a shift in vegetation. Species-rich grasslands are gradually replaced by dwarf shrubs such as heather. Researchers said while this change can increase plant biomass, it also alters what happens below ground.

Heather and other shrubs form close relationships with specialist fungi that slow the decay of plant litter, they said. This leads to a build-up of short-lived carbon at the surface — but at the same time stimulates the breakdown of older, mineral-protected carbon deeper in the soil as fungi scavenge nutrients to support growth.

Wetter soils, common in northern uplands, can further weaken the mineral bonds that normally protect MAOC, leaving long-stored carbon vulnerable to loss, the study found.

“Viewing livestock removal as universally beneficial overlooks the fact that carbon exists along a spectrum of durability,” said Dr Shangshi Liu of Yale University, who co-led the study.

“When slow-cycling carbon declines, grassland carbon stocks may become more vulnerable to future climate change.”

The findings come at a critical time for environmental management policy in the UK and globally, as governments develop land-use frameworks to meet net-zero targets. For decades, land managers have assessed climate benefits by measuring “total carbon stocks”. Authors said the new research shows that this approach can be misleading, as increases in fast-cycling carbon may mask declines in the forms that matter most over time.

Professor Richard Bardgett of Lancaster University, who initiated the study, said the results pointed towards a more nuanced approach.

“Maintaining low-intensity grazing in upland grasslands — which cover large areas of Scotland and the wider UK — appears important for protecting the most stable forms of soil carbon,” he said.

The study was funded by the UK Natural Environment Research Council (NERC), the Biotechnology and Biological Sciences Research Council (BBSRC), the European Research Council (ERC), and Yale Center for Natural Carbon Capture fellowship.