The mire at Westhay Moor National Nature Reserve is one of the largest remaining fragments of lowland raised bog in the South West. Yet over a century ago the peat there was hand cut for fuel. In recent decades, the areas around it have been excavated on an industrial scale to the underlying clay for compost production.
Right Tree, Right Place: Restoring Somerset’s Peatlands
The right tree in the right place can provide many benefits to nature and help in the fight against climate change. However, the wrong tree in the wrong place can actually cause more harm than good.
Landscape view of Westhay Moor nature reserve, 2023. Photo: Sian Russell
The result? Well, the result has been a struggling, rare habitat at risk of drying out when it should comfortably be wet and boggy. Where drainage has dried out the peat, trees and scrub have been moving in. However, years of dedicated scrub removal by our Reserves Team and volunteers have not quite managed to turn the tide on this intrusion.
Peat forms over many years when plants die and fall into waterlogged conditions. Those wet conditions halt the decay process and over time layers upon layers of dead plants, and the carbon they took in from the atmosphere when they were alive, are stored as peat. The process is very, very slow.
In some places on the Somerset Levels and Moors, the peat can be more than five metres deep. The peat started forming over 6000 years ago, but since Roman times people have been gradually draining this wetland habitat, reclaiming the land and using the peat - originally for fuel and more recently for compost.
Draining peatlands allows oxygen in and kickstarts the decay process meaning that the carbon that has been locked up for millennia is being released to the atmosphere. We estimate that 10% of Somerset’s carbon emissions come from the Levels and Moors.
Drier conditions on the surface peat allow non-peatland species to move in like bracken, bramble and scrub — followed by larger trees.
Westhay - Sam Glasspole
Unfortunately, trees can damage peat in two ways. First, they act as water pumps, removing water from our wetland habitat and transpiring it to the air. Second, their leafy canopy acts as an umbrella, stopping rain from reaching the surface of the peat and shading out rare, low-growing peatland species. This pushes the balance further toward drier conditions, allowing other non-peatland species to move in, and so conditions spiral further away from the waterlogged state a peatland needs to stay healthy.
The right tree in the right place is key. Trees and scrub damage the hydrology of a peatland. Although they lock up carbon from the atmosphere, they are only decades old. By comparison, the carbon stored in peatlands in areas like Westhay Moor is over 3,000 years old.
So what about carr or wet woodland? Yes, there are some types of wet woodland that are peat forming, some of which we had at Westhay Moor up until around 2000BC, with species like alder and willow, which can cope with being permanently waterlogged. This is where the right tree in the right place comes into consideration. Peat forming wet woodland exists in times of very wet climate with year-round waterlogged ground conditions, this balances out the drying effect of trees. However, on our damaged peatlands the water drains away too quickly, accelerating the drying effect of the trees on what should be a wetland habitat.
Pioneering tree species like birch are typically some of the first species to invade dry, degraded peatlands as they can cope with some waterlogging for part of the year, so it is not a surprise to find them on the remaining damaged peatland areas at Westhay Moor. Where the birch trees have made conditions dry enough, species like oak have been able to move into places they simply shouldn’t be and counter the efforts of decades of conservation management to preserve the peat that remains at Westhay Moor. Thankfully, with funding from the Nature for Climate Peatland Grant Scheme and via the Valencia Communities Fund (through the Landfill Communities Fund) Somerset Wildlife Trust has been able to make some bold moves over the past 18 months to remove the trees and scrub which have been damaging the peat on some areas of Westhay Moor.
Peatlands have been exploited and misunderstood for too long. Many people think that peat in compost is a thing of the past, because there has been talk of banning it for over a decade – but this is simply not the case. The last government promised a ban on peat compost sales before the end of 2024 but this did not happen.
At Somerset Wildlife Trust, we will continue to campaign for a complete ban on all peat-containing products, including peat compost, but in the meantime, it’s really important that we continue to raise awareness about our precious peatlands and their incredible ability to store carbon when left untouched.