The peatlands of Dartmoor

Hidden amongst Dartmoor’s rugged expanse lies an ecological treasure – peatlands. Areas of peat, predominately formed by blanket bogs, are estimated to cover 158 ± 101 km² of Dartmoor National Park, and contain 13.1 megatonnes of carbon. But over decades, if not centuries, vast expanses have been degraded due to pressures such as: drainage or extraction for agriculture, overgrazing, burning, or cutting for fuel. In fact, 29 km² has been mapped as significantly and directly ecohydrologically degraded.

Restoring Dartmoor’s peatlands

Since 2009, the Dartmoor Mires Project, now the South West Peatland Partnership have been working on the huge undertaking of restoring Dartmoor’s peatlands. The partnership is a collaboration between local and regional government agencies, non-governmental organisations, businesses, landowners, commoners, and farmers. A team of researchers from the University of Exeter have been working alongside the restoration practitioners for over a decade, co-creating research questions and building a story about the impacts of peatland restoration on Dartmoor.

Flat Tor Pan: a case study

A key part of the story comes from Flat Tor Pan, an area located on Dartmoor’s high moor. The site has peat depths between 3.6 and 4.0 metres thick, and has dendritic and gully erosional features. In 2012, monitoring equipment was installed by the University of Exeter team to quantify the impacts of restoration work. After two years of monitoring baseline conditions, restoration work was carried out in 2014, setting the foundations for what we hope becomes an inspiring tale of recovery. In our paper, we present the data collected between 2012 and 2018, capturing the short-term response to the restoration works.

Transforming the hydrology

Restoration activities at Flat Tor Pan sought to alter the way water flowed through the landscape. To do this peat, from nearby borrow pits or small protuberances, was used to block gullies and disconnect flow pathways between dendritic erosional features. The impact on how water moves around the site was astounding. Peak storm flow was reduced by a staggering 49%, reducing the erosive power of rainfall events and the risk of further erosion of the peat.

The rise of water tables and methane’s paradox

The blocks have also immediately transformed the sparsely vegetated and bare peat areas within the dendritic erosion pathways into pools, increasing mean water tables from 0.3 cm below the ground level before restoration to 6.4 cm above after. In the surrounding areas, water tables have stabilised following restoration. And, critically, the water tables in the surrounding are now 6 cm closer to the surface during dry periods, decreasing the volume of peat that is able to oxidise. These raised water tables have led to an increase in methane emissions. However, this isn’t an unexpected outcome of restoration. Pristine peatlands emit methane, while a more potent greenhouse gas than carbon dioxide, it has a shorter residence time in the atmosphere.

The long road to recovery

Despite significant hydrological improvements, our study found minimal impact on both fluvial and gaseous carbon exports. The absence of immediate change stems from the relatively healthier starting condition of the peatland in this Dartmoor region, when compared to other locations. Here, substantial shifts in vegetation communities are likely the key to altering carbon production and cycling. Given the decadal to centennial timescales of these ecosystems, patient and realistic expectations from all stakeholders are essential, allowing these landscapes the time and space they need to rejuvenate.

Peatland restoration matters

While restoring the tiny imbalance between the carbon dioxide (CO₂) drawn down through photosynthesis and the CO₂ released by respiration, is a key driver of peatland restoration, these landscapes are also sanctuaries for rare and specialist wetland species. As the peat dries out and their habitats are lost, the conditions become less favourable to these specialist species and they are outcompeted by generalists. By restoring and safeguarding these habitats, we are also creating a more resilient space for nature.

Looking to the future

It’s now 5 years after the data presented in our paper was collected, and there is exciting news. Significant vegetation change is occurring on the site. While altering the hydrology is key, vegetation is a key driver of the carbon cycling of peatlands. To better understand how these landscapes recover over longer timescales, we are revisiting the site as part of a broader project. So, stay tuned for updates as we build a picture of what the story of peatland restoration looks like for Dartmoor.