Background and Funding
Established in 2011, this experiment addresses identified gaps in relation to the relatively scarce (and sometimes conflicting) evidence for the impacts of current and possible alternatives to burn-rotation grouse moor management of heather-dominated blanket bog on carbon, water and biodiversity. It is conducted across three peat bog sites in north-west England: Nidderdale and Mossdale in North Yorkshire, and Whitendale in East Lancashire.
map of sites in north-west England [Maps downloaded from MiniScale®; Ordnance Survey data using the EDINA Digimap Ordnance Survey Service
The project follows on from the previously Defra-funded peatland project BD5104 'Restoration of blanket bog vegetation for biodiversity, carbon sequestration and water regulation'. The project's initial phase ran from 2011 to 2017, with a second phase until 2022. Phase 2 funding reflected a multi-funder consortium consisting of Yorkshire Water Services (YWS), United Utilities (UU), the Moorland Association (MA), the British Association for Shooting and Conservation (BASC) and the Yorkshire Peat Partnership (YPP). The YPP and Natural England (NE) also support two NERC-funded PhDs and provided valuable guidance within this project. The consortium met at least annually as the Project Advisory Group. More recently, the MA has provided bridge-funding, which together with NERC funding (as part of a Highlight Topic project) now extends the project until 2026.
ground-level images taken winter 2012, showing dominance of heather & sedge (chiefly cottongrass)
Rationale
Over 25% of the UK land area is covered by uplands, a large proportion of which comprises blanket bog. Blanket bogs are wetlands forming under high precipitation and predominantly cool conditions, where high water tables and acid conditions suppress decomposition and favour Sphagnum moss growth and ‘active’ peat formation. This peat accumulation of active bogs in the uplands represents a major UK carbon (C) stock which is linked to a range of key ecosystem services, particularly C storage, flood prevention, drinking water provision and biodiversity. Although active blanket bogs are a long-term C sink, they have the potential to emit large amounts of methane, potentially causing a net positive contribution to greenhouse gas (GHG) emissions. Importantly, the UK has about 15% of the globally rare blanket bog habitat, containing many specialist species of birds, invertebrates and plants. These upland habitats also attract many visitors and support local economies including through livestock farming and game management.
mossdale
About 5-15% of the UK upland area, and 30% of UK blanket bog, is managed for red grouse by encouraging ling heather (Calluna vulgaris). Since around 1850, with the onset of driven shoots, grouse moors have been managed by drainage and rotational heather burning to encourage heather dominance over other bog vegetation and their management has been linked to adverse conditions of blanket bogs with negative impacts on key ecosystem services linked to carbon, water and biodiversity. Moreover, climate change poses another challenge, as changes in rainfall patterns with an increasing frequency of summer droughts, are a threat to future bog development.
Recently, there have been considerable efforts to reverse this degradation and increase resilience to climate change impacts by blocking drainage grips and using alternative mowing management to encourage ‘active’ blanket bog vegetation. Despite the ecological and economic importance of blanket bogs, few robust data are available on UK blanket bog C balance, net GHG emissions and their controlling factors, and on how heather burning or alternative mowing managements affect C storage and other key ecosystem services, and if and how mowing differs in its effects on vegetation composition and structure compared to burning and leaving bog ‘unmanaged’.
cottongrass - eriophorum vaginatum - AT MOSSDALE SITE, THREE YEARS AFTER MOWING
Aims
The overall purpose of the project is to assess the ecological and environmental impact of different management techniques on areas with predominant heather coverage. This is based on including feasible grouse moor management techniques (i.e. burning, mowing and uncut) as part of a manipulative experiment to provide scientifically sound and meaningful data upon which to base policy advice and subsequently inform management decisions, considering both, environmental and socio-economic implications.
Experimental Design
The project monitors changes in peatland habitat status indicator variables in response to different management (i.e. treatments). The main treatment is to mow/cut heather areas in-line with current large-scale mowing management techniques and then compare that to control areas that have undergone the ‘business as usual’ burning regime.
Our experimental design incorporates two statistical approaches:
large catchment-scale (most policy-relevant) manipulations and monitoring;
small plot-scale (most scientifically-relevant) manipulations and monitoring.
The Before-After Control-Impact (BACI) approach - comparing the time series behaviour of pre-treatment versus post-treatment - allows us to establish a robust, replicated experimental study. Two major catchment-scale treatments and several additional restoration plot-level treatments are therefore being applied across three sites.
See further information on the three bog sites and additional detail on the experimental design.
![burning & mowing treatments at the three sites [from left to right, Nidderdale-mossdale-whitendale]](https://images.squarespace-cdn.com/content/v1/54f09635e4b02703b86201fa/1539269522893-TY7O0CDT236O4C42POO8/Burning+%2B+Mowing+Treatments.png)
burning & mowing treatments at the three sites [from left to right, Nidderdale-mossdale-whitendale]
Results To Date
View the publications list for results to date. In addition to the 5 year Defra report (BD5104) there is now also the 10-year report to the Project Advisory Group (PAG) now available for download a short summary and full summary version are also available. The schematic below summarises the investigated parameters and their ecosystem services-related linkages across the landscape.
Schematic network of the main linkages between management impacts on plant-soil-water processes and associated key ecosystem services aspects (related to carbon, CO2-equivalents (CO2-eq), greenhouse gas emissions (GHG) water and biodiversity) across a generic catchment area containing upland areas with blanket bog. Processes and parameters investigated in this project are shown in bold, dashed red line outlines represent identified important but so far understudied processes (i.e. soil chemistry, soil microbes and eco-hydrology) linking key aspects. Note that the impacts are reaching far beyond the upland area with indirect effects on livelihoods in cities connected by water, food and economy.
The main outcome so far supports that heather burning, cutting or leaving it unmanaged should all be available tools to upland land managers in the fight against climate change and biodiversity loss. Key findings of the 10-year report include:
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• Compared to uncut plots, burning and mowing support increased vegetation diversity, with increased levels of Sphagnum mosses, which are supportive of peat formation.
• The uncut option showed lowest plant diversity as well as limited recovery of supportive peat-forming mosses.
• On sites which had been cut or burnt a greater density of ground-nesting birds was predicted as tall heather severely limits appropriate nesting sites.
• Nutrient content of heather and sedge shoots was improved after either cutting or burning, but particularly after burning, for elements relevant as nutrition for grazing animals but also to carbon uptake. This is likely because of the ash fertilisation.
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• Unmanaged heather areas took up most carbon overall throughout the study. However, as time progressed and the heather aged, these areas absorbed less than half the levels of carbon compared to the start of the study. Additionally, over time the water table dropped and the peat became drier, increasing decomposition of peat.
• During prescribed burning carbon is released into the atmosphere as well as particles associated with air pollution.
• Carbon loss from the burnt areas are initially higher than from cutting, but then it falls as vegetation regrows and takes up carbon. After about 6 years the predicted carbon balance for the burnt plots showed a carbon sink and after ten years it absorbed more than twice the carbon per year compared to mown or unmanaged areas.
• There is no large initial carbon release during cutting but the brash left on the surface decomposes and over time releases most of the carbon contained to the atmosphere.
• The predicted carbon balance per year from cut areas switches from overall carbon release to overall uptake around 8 years after management, at which point cut sites overtake unmanaged sites.
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• Overall, the wetter the site, the higher the methane emissions.
• Cutting resulted in higher methane emissions, likely due to an increase in wetness combined with higher sedge abundance (allowing plant-mediated transport of methane, bypassing oxidation).
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• Whilst cutting created initially wetter conditions (reflecting brash effects on infiltration and reduced evaporation losses), burnt plots became the wettest whereas uncut plots became drier over time.
• Stream flow was lower in cut than burnt catchments, but overall this was less than 10% (only two of three sites showed this effect).
The report also considered the increasing threat of wildfire and its relation to management techniques, as unmanaged heather-dominated peatlands will eventually burn, likely during a warm and dry summer, with catastrophic carbon losses when the fire burns into the peat. However, although both cutting or controlled burning prevent such damage, whereas cut brash mostly decomposes, burning creates to decomposition resistant charcoal. This part of the project has now been included in a NERC funded Highlight Topic project (IDEAL UK FIRE), which is led by the University of Birmingham.
Further Information and Data Repository
Full details on the project are available via the main project website. Data are available on request from the Principal Investigator Andreas Heinemeyer and Defra’s recent report BD5104 is now available from the bibliography.
Research Updates
Media
Radio (25 January 2023): Andreas Heinemeyer was interviewed for the Farming Today BBC Radio 4 programme about the 10-year Peatland-ES-UK project report and findings on management impacts on heather-dominated peatlands for carbon, water and biodiversity. Listen to it on BBC 4 Radio [Available until 15 February 2023]
