What 10 Years of Research Tells Us About Protecting Our Peatlands
- Rob Beeson
- Mar 25
- 7 min read
Beneath our moorlands lies a hidden treasure: peatlands. These unassuming ecosystems are actually powerhouses when it comes to storing carbon, playing a crucial role in the fight against climate change.
Think of peat soil as a super-efficient carbon sponge. Despite covering only a tiny fraction of the world's land (about 3%), it holds a whopping 30% of all the organic carbon found in soil. That's a massive amount of carbon locked away, preventing it from contributing to greenhouse gases in the atmosphere.
And here's a fascinating fact: the UK is particularly important in the peatland story. We hold a large chunk of a rare type of peat bog known as blanket bog. In fact, around 15% of the world's blanket bog can be found right here in the UK uplands. This gives us a unique responsibility and opportunity to protect these natural carbon vaults.
But keeping these peatlands healthy isn't as simple as leaving them untouched. For centuries, these landscapes have been shaped by human management, often involving practices like heather burning. This brings us to a crucial question: how should we manage our moorlands in the face of a changing climate?
For the past decade, a significant research project called PEATLAND-ES-UK has been digging deep into this very question. This long-term study has been meticulously comparing different approaches to managing heather moorland: traditional burning, alternative mowing, and simply leaving areas unmanaged. The goal? To understand the impact of these methods on everything from biodiversity and carbon storage to water regulation and greenhouse gas emissions.
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The PEATLAND-ES-UK Project: A Decade of Discovery
Why was this project so important? Well, despite a lot of interest and debate around moorland management, there was surprisingly little solid scientific evidence about what actually works best. Existing studies often had limitations, like being too short-term or not properly accounting for factors like historical drainage. This led to conflicting findings and a lot of uncertainty.
Natural England, the government's advisor on the natural environment, highlighted these knowledge gaps in a 2013 report. They called for robust research to investigate the long-term effects of heather burning and other management techniques on key aspects of peatland health.
The PEATLAND-ES-UK project rose to this challenge with a rigorous study design. Here's what made it stand out:
Multiple Sites: The study spanned several locations across northern England, representing a range of peatland conditions.
Paired Catchments: At each site, similar areas (catchments) were chosen and monitored to ensure fair comparisons between different management approaches.
BACI Design: This stands for Before-After Control-Impact. Researchers carefully monitored the sites before any management took place, then implemented different treatments (burning, mowing, no management), and continued monitoring afterwards. Crucially, they also included unmanaged control areas to see what would happen naturally.
Long-Term Monitoring: The ten-year duration (and ongoing nature) of the project is vital for understanding the full impact of management practices over time.
This thorough approach allows scientists to be much more confident that any changes they observe are actually due to the management techniques being studied, rather than other factors.
Key Findings: Peeling Back the Layers of Moorland Management
So, after a decade of careful observation and data collection, what has PEATLAND-ES-UK revealed? The findings offer valuable insights into the complex world of moorland management.
Vegetation: A Dynamic Landscape
One of the study's aims was to see how burning and mowing affected the plant life, particularly in areas dominated by heather.
Reducing Heather Dominance: Both burning and mowing were effective in reducing the amount of heather cover, creating space for other plant species to thrive.
Boosting Biodiversity: Interestingly, both management approaches appeared to support a healthy bog vegetation. They helped open up the dense heather canopy, allowing Sphagnum mosses (important peat-forming species) and other mosses, shrubs, herbs, and sedges like cotton-grass to increase.
Short-Term Changes: In the initial years after management, burnt areas had more bare ground, while mown areas had more cut heather (brash). However, these effects were temporary, and after about four years, the managed plots looked similar again.
Heather Regrowth: Heather regrew after both treatments, initially slightly faster on mown plots, but by the four-year mark, height and cover were similar.
The Heather Beetle Wildcard: A significant and unexpected event occurred during the study: severe heather beetle attacks. These outbreaks, unrelated to the management being studied, caused extensive damage to the heather, particularly on burnt plots at wetter sites and mown plots on the driest site. This had a big impact on carbon levels.
Carbon Storage: The Balancing Act
Peatlands are carbon powerhouses, so understanding how management affects their ability to store or release carbon is crucial. The study looked at various aspects of the carbon flux, including carbon released during burning, decomposition of cut heather, carbon absorbed by growing plants, and carbon released from the peat itself.
The Impact of Heather Beetle: The actual measured data showed that both burnt and mown areas released more carbon than they absorbed over the ten years, largely due to the heather beetle damage. Uncut plots, which weren't as affected by the beetles, actually took up carbon overall.
Predicted Carbon Balance (Without Beetle Effects): When researchers accounted for the beetle outbreaks, the picture changed significantly. Their predictions suggest that all three management approaches would likely result in a net uptake of carbon over ten years. Uncut areas were predicted to absorb the most, followed closely by burnt areas, with mown areas absorbing the least.
Long-Term Trends: Unmanaged heather areas, while initially a strong carbon sink, showed a slowing rate of carbon uptake over time as the heather aged and the peat became slightly drier.
Burnt Areas: Burning initially releases a lot of carbon, but as vegetation regrows, these areas quickly become carbon sinks, potentially absorbing the most carbon per year in the long run. The stable carbon in charcoal left after burning may also play a vital role in long-term carbon capture.
Mown Areas: Mowing avoids the immediate carbon release of burning, but the decomposing cut heather releases carbon gradually over a longer period. Mown areas take longer to become carbon sinks compared to burnt areas.
Greenhouse Gas Emissions: Beyond Carbon Dioxide
While carbon dioxide is a major greenhouse gas, the study also looked at methane, which has a much stronger warming effect over shorter timescales.
Methane Release: Uncut areas released significantly more methane than managed areas, particularly during warmer and wetter periods. Mown areas released an intermediate amount, and burnt areas released the least.
Reasons for Differences: The higher methane emissions from uncut areas are still being investigated. The lower emissions from burnt areas may be due to charcoal, which can help convert methane to CO2 in the soil. Mown areas had more sedge cover, like cotton-grass, which can act as a pathway for methane to escape from the peat.
Water Dynamics: Keeping Peatlands Wet
A high water table is crucial for healthy peat formation and carbon storage. The study monitored water table depths across the different management areas.
Unmanaged Areas: Water tables in unmanaged heather gradually dropped over the study period, leading to drier peat.
Mown Areas: Mowing initially led to slightly wetter conditions, but this effect decreased over time, and eventually, these areas also became drier.
Burnt Areas: Burnt areas were initially slightly drier but became wetter in the longer term.
The 12cm Threshold: The study supports the idea of a critical water table depth of around 12 cm below the surface. Peatlands wetter than this are more likely to absorb and store carbon, while drier areas are more prone to releasing it.
Water Quality and Flow: Minor Management Impacts
The study found that the differences in water flow and quality (specifically dissolved organic carbon) between burnt and mown areas were relatively small compared to the influence of pre-existing site characteristics like rainfall and drainage. Mowing might slightly slow down water flow due to the presence of brash.
Wildfire Risk: A Growing Concern
With climate change increasing the risk of wildfires, the study considered how different management approaches might affect this.
Unmanaged Heather: Leaving heather unmanaged leads to a build-up of dry vegetation (fuel load) and a gradual drying of the peat, significantly increasing the risk of large and damaging wildfires.
Managed Areas: Both burning and mowing reduce the fuel load. However, cut heather left after mowing can also become dry and act as tinder. Prescribed burning is typically done under controlled, wet conditions.
Looking to the Future: Informed Decisions for Our Moorlands
The PEATLAND-ES-UK project provides valuable insights, but it's important to remember that these are findings from the first decade of a long-term study. To truly understand the full picture and inform effective moorland management policies, continued research over at least a complete management cycle (around 20 years) is essential.
However, even at this stage, some key takeaways are emerging:
Active Peatlands: All three management approaches can support active and healthy peatlands capable of storing carbon.
Trade-offs: Both burning and mowing have initial carbon costs but can lead to increased carbon absorption later on.
Site Matters: The best management approach likely depends on the specific conditions of the site, particularly its wetness. Prescribed burning may be more suitable for wetter sites, while mowing could be a better option for drier areas. The threshold of a water table around 12 cm below the surface seems important here.
Unmanaged Areas: While unmanaged areas initially act as strong carbon sinks, the slowing carbon uptake, increased methane emissions, and high wildfire risk suggest potential long-term negative impacts.
The complexity of these ecosystems highlights the need for careful consideration and the use of robust scientific evidence to guide moorland management decisions. Projects like PEATLAND-ES-UK are crucial for moving beyond opinion and towards informed strategies that protect these vital landscapes and the crucial role they play in our environment.
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