Appendix 5: Mitigating and adapting to climate change

Protecting existing carbon (peat)

Upsides

i) Grouse populations can benefit from improvements to peatland habitat and soil condition. Over the last 25 years grouse moor managers have re-vegetated bare peat and blocked grips (drains) primarily cut for agriculture. Unblocked peat drains can increase peatland carbon losses by 9t CO₂e/ha each year⁹⁷. The Moorland Association calculates that its member's actions have reduced CO2 emissions by 61,126 tonnes per year over the last 10 years.

ii) The impact of wildfires on peatland carbon sequestration and fluxes¹¹⁰ is of concern given anticipated increases in their occurrence due to climate change. More detail is presented in Appendix 4.2: Reducing the risk of environmental hazards – wildfire mitigation.

iii) Tree planting on organic rich soils will probably not lead to an increase in net carbon sequestration within a native tree ecosystem even several years after planting¹¹¹. The loss of soil carbon cancels out the increase in the tree’s biomass carbon over decades. GMM provides a viable economic and biodiversity alternative to tree planting and the retention of heather moorland and blanket bog.

Downsides

iv) Three studies investigated recent burning trends (in area and timing): 

• Allen KA et al (2016) Prescribed moorland burning meets good practice guidelines: A monitoring case study using aerial photography in the Peak District, UK. Ecol Indic 62:76–85.
• Douglas DJ et al (2015) Vegetation burning for game management in the UK uplands is increasing and overlaps spatially with soil carbon and protected areas. Biol Conserv 191:243–250.
• Thacker J, et al (2014). Burning in the English uplands: a review, reconciliation and comparison of results of Natural England’s burn monitoring: 2005–2014. Natural England, Peterborough, UK.

v) However, there are weaknesses in the data that these three studies present: no data was presented for overall burning trends in the last 5-10 years; remote-sensing technology (aerial imagery) was used in all studies but only one used ground-truthing to confirm the data (Allen et al (2016)); and, temporal trends and burning rotations were considered in only two of the studies (Allen et al (2016) and Thacker et al (2014)). A recent study used satellite imagery with finer resolution, more frequent return intervals and broader coverage to determine extent and burn frequency during the period 2015-2020¹¹². This found that area managed varied by moorland region and year with the shortest average rotation on the North York Moors (20 years) and the longest the North Pennines (66 years). This study did not compare extent and frequency with earlier periods and we believe there is still no accurate assessment of whether burn area or frequency has changed compared to previous decades.

vi) Methane fluxes increase with rising water tables and warmer temperatures¹¹³. Wetlands, wildfires and thawing permafrost are projected to be natural sources in the future⁴. Methane makes a significant contribution to net GHG emissions on grouse moors³⁰ but values are similar to rewetted bogs¹¹⁴. Latest emission factors (EF)⁹⁷ demonstrate this with a revised EF for rewetted bog of 3.91 (as opposed to 0.81 previously reported in 2017¹¹⁵).

Challenges

vii) English grouse moors include 41% of England’s peat area but emit only 1-5% of total peatland emissions in England, depending on estimates of area, peat condition and level of emissions⁸. This compares very favourably to lowland arable agriculture which covers c.24% of England’s peat area and which are the source of 64% of peatland GHG emissions (23.38-28.45t CO2e/ha/yr⁹⁷).

viii) Many, including Natural England¹¹⁶, recognise that controlled burning can complement peatland restoration and climate change mitigation through reducing emissions, but the available short-term data on it is inadequate to accurately assess the current contribution²⁴ (see also opportunities). This data gap means that the negative narrative around heather burning⁶⁰ cannot be addressed, leading to public policy failing to recognise the potential value of vegetation management in minimising fire and erosion threats to upland carbon stores.

ix) The individual effects of controlled burning and drainage on peat function have not been determined and so the two become conflated⁶⁰. Controlled burning has been shown to lower water table depth for up to 10 years in some areas¹¹⁷. But drainage has had the most significant effect on peatland hydrology given its spatial extent. Moorland ditching and afforestation have been identified as the two most important factors affecting the hydrology of upland peatland¹¹⁸. The peak rate of drainage was estimated to be 100,000 ha/yr in 1970 in response to public grants which supported this activity for the purposes of improving hill farming.

x) Cutting and leaving the brash has implications for net zero ambitions. Its decomposition releases GHG emissions, possibly ‘locking away’ less C than via charcoal from burning¹¹⁹.

Opportunities

xi) The historic and current production of biochar following landscape fires (also called black carbon) is not currently accounted for in UK carbon budgets^119,120, yet biochar production by controlled fires could be a significant sink for atmospheric CO₂^121,122. Failing to account for biochar sequestration is probably leading to overestimates of the impact of burning on net C stocks and fluxes in upland soils. Biochar also has the potential to mitigate other GHG emissions (such as methane^123,124) and aid peatland restoration through its interaction with the soil microbiome¹²⁵and benefits to soil structure and stability¹²⁶.

xii) Long-term research studies should be used to inform ecologically driven burning practices. Research assessing carbon accumulation over the last few hundred years on blanket bog sites under rotational grouse moor burn management and found that “All sites showed considerable net carbon accumulation during active grouse moor management periods”¹¹⁹. Much of this effect may be due to vigorous plant regrowth after burning.

xiii) Over long time scales (>50 years) controlled burning can help transfer carbon captured by photosynthesis to soil microbes, with no net loss of carbon compared to pre-burn levels¹²⁷.

xiv) Managed burning rotations could complement peatland restoration as controlled burns may have a role in suppressing methane emissions^110,128. Dwarf shrub heath may be a better methane modulator than grass¹²⁹.

xv) Research is needed to define a functioning ‘healthy’ peatland in today’s climate¹¹⁸. Today’s peatland may be a completely different type of healthy, functioning peatland from that which formed a millennia ago. For example, bio-climatic envelope models predict that active peat formation will decline in the absence of suitable climatic conditions but these do not account for feedbacks that may act as buffers to change such as climate-peatland SOC (Soil Organic Carbon) feedbacks¹³⁰. In addition recent research has identified a regime shift or tipping point where peat accumulation started to re-occur naturally c100-150 years ago; the reasons for it not being explained solely by climate with local topographic conditions likely to be important in creating suitable hydrological conditions¹³¹.

Storing more (sequestering) carbon

Upsides

xvi) The ONS estimate that mountains, moorlands and heaths sequestered 1.99 MtCO2e in 2017¹³ relates entirely to estimated upland grassland emissions. Upland peatlands are thought to emit carbon at an average rate of 3tCO₂e/ha rather than acting as a sink¹³². The contribution of heather and biochar from burning to upland carbon budgets is likely to have been underestimated in previous carbon inventories¹³³. However the potential benefit to carbon sequestration of atmospheric nitrogen deposition¹³⁴ may be declining as pollution levels fall.

xvii) Research is needed into the factors that influence the amount of biochar produced and its residence time such as weather conditions, fuel loads, feedstocks, fire types¹³⁵, fire residence and fire temperature¹³⁶ in order to maximise its benefits to carbon sequestration and peatland restoration.

Challenges

xviii) ‘No burn management’ is being promoted without a good understanding of its implications for ecosystem services such as biodiversity or long-term carbon cycles at a landscape scale¹³⁷. For example, heather and grass cutting is being promoted without adequate assessment of impacts such as mowers flattening the surface and affecting botanical biodiversity¹³⁷.

xix) Public media ‘framing’ of upland vegetation burning as synonymous with the burning of peat is preventing an appropriate analysis of the effects on carbon budgets over burning cycles and in the comparison of managed burning and wildfire effects on carbon fluxes⁶⁰.

xx) Public policy is not adapting to new evidence. Recent reports suggest much sequestered peatland carbon will not become part of the long term store^138,139, yet public policy on carbon budgets states that “peatland … can continuously accumulate carbon under water-logged conditions at a rate of around 1mm per year”¹⁴⁰. See also Appendix 1 of GWCT Peatland Report 2020⁸.

xxi) There remains a clear need for better data on long term carbon stocks, fluxes and how these are affected by wetting and burning, and for a more flexible interpretation and implementation of findings through management^8,137. Currently the available data is just from a few sites and must be interpreted with caution.

Opportunities

xxii) Research suggests that some peatlands may naturally restore without management intervention resulting in the re-vegetation of bare peat areas¹⁴¹ where climate and local topographic conditions are favourable¹³¹. See also Box 4.1.5.4 in the main report.

xxiii) There is still insufficient data to judge when restoration projects result in the conversion of a peatland from source to sink. Recent additions at the peatland surface do not indicate that the peatland as a whole is a C sink – “the addition of new mass needs to exceed all losses throughout the whole profile for this to be the case”¹³⁸. Research into when and if a restored peatland becomes a carbon sink also needs to include the identification of appropriate metrics to monitor success.

xxiv) Carbon cycling relies on the soil microbiome yet little is understood about the process involved and how this affects peatland resilience and function. Given that climate change could alter soil conditions (predominantly the water table), understanding the impact that this will have on microbial processes is important. Microbial processes may be a way of monitoring peatland restoration success¹⁴².