British Ecological Society (BES) – Written evidence (NSD0013)

 

The British Ecological Society (BES) is the biggest scientific society representing ecologists in Europe, with more than 6,600 members. The BES has recently published a report that analyses the potential of nature-based solutions (NbS) to address the climate crisis and simultaneously deliver biodiversity benefits across all main UK habitats. More than 100 experts contributed to the report, providing a comprehensive summary of available scientific evidence and policy recommendations from the ecological community. This consultation response was drafted by members of the BES’ Policy Team and Policy Committee, with expert input from Christian Dunn (Bangor University). The Royal Society of Biology has reviewed and supports this response.

 

1. What is the potential scale of the contribution that nature-based solutions can make to decarbonisation in the UK?

It is important to realise that nature-based solutions (NbS) are not enough to decarbonise countries’ economies and should only be used to mitigate the residual emissions after rapid and significant emission reductions across all sectors. For this reason, carbon storage in ecosystems should be accounted separately to reductions in carbon emissions.

 

The vast majority of terrestrial and marine habitats provide NbS by sequestering carbon. Some, such as peatland and woodland, are better researched and more effective than others, yet heathland, grasslands, agroforestry, hedgerows, seagrass and saltmarsh can all provide benefits. All are reviewed in the report recently published by the British Ecological Society.

 

Table 1 shows the most important habitats for carbon sequestration. Peatlands store the highest amount of carbon per hectare by far (this carbon has been stored for thousands of years), followed by native woodlands. The highest sequestration potential, i.e. the annual flux of sequestered carbon per year, is offered by woodlands, which continue to absorb carbon over centuries (the sequestration rate declines over time, but old woodlands become significant carbon stores)[1]. If overseas territory waters are included, marine sediments are most important for carbon sequestration, due to their extremely large area (despite low sequestration rates per unit area)[2].

 

At present, we estimate that around 15% of UK emissions are sequestered by NbS (the most important habitats are included in Table 1, but other habitats also contribute to sequestration). With dedicated restoration of NbS across different habitats, including large-scale tree planting, this share could reach 30% of UK emissions, based on 2019 data and including avoided emissions in peatlands. In fact, peatlands are net emitters of carbon in their degraded state, and restoring drainage and other physical damage to peatlands could rapidly reduce UK carbon emissions by around 5.7%. Naturally, the percentage of emissions sequestered will increase as emissions decrease over time. The calculated figure contains many assumptions and uncertainties, and should be considered a ball-park estimate rather than an absolute value. However, it is clear that alongside large emissions cuts, NbS can play an important role in offsetting residual emissions.

 

It is important to realise that NbS provide co-benefits in all habitats, besides carbon sequestration, including biodiversity protection and restoration, climate adaptation (localised cooling, flood prevention, reduced storm and wave action, etc.) and benefits for human well-being, including mental health. These multiple benefits are one reason why multiple habitats should be considered in the management and restoration of NbS, rather than just focus on woodlands and peatlands. Management and restoration of NbS can also provide numerous green recovery jobs, and have shown to be highly economically beneficial in cost-benefit analyses.


Table 1. Potential carbon sequestration of NbS in woodland, peatland and marine sediments

Habitat

Area in UK (ha)

Carbon store (t.C.ha-1)

Carbon sequestration (t.CO2.ha-1)

Potential restoration (ha)

Carbon sequestration (t.CO2.y-1)

Carbon sequestration as % of UK emissions

Notes

Woodland

3,150,000

346

6.64

3,000,000

Current = 20,196,000

 

Potential = 40,836,000

Current = 4.5

 

Potential = 9.0

Native broadleaf forests provide considerably better biodiversity benefits and are recommended over conifer plantations for this reason. Careful spatial planning will be required to discern the optimal location for tree planting to avoid emissions associated with planting on carbon-rich soils.

Peatland

2,600,000

1,150

-8.85

n/a

Current = -23,010,000

Potential = +26,000,000*

Current = -5.1

Potential = 5.7*

*This is mainly a reduction in CO2 emissions from degraded peatland, rather than sequestration.

The carbon sequestration figure is negative because at the moment peatlands are net emitters.

Marine Sediments

88,543,000 in the EEZ [3]

680,558,600, including OTs[4]

26

0.06

n/a

Current and potential = 5,312,580 (EEZ)

40,833,516 (including OTs)

1.2 (EEZ) or 8.9 including OT

Assuming that sequestration figures from UK shelf waters apply internationally

Source: own calculations, based on the figures collected in the BES report.


2. What major scientific uncertainties persist in understanding the effects of nature-based solutions and affect their inclusion in carbon accounting, and how can these uncertainties be addressed?

The uncertainties and research gaps around NbS are summarised in Annex II of the BES report. In general, sequestration estimates vary considerably between studies, and may depend on many factors such as location, environmental conditions, different species and estimation methods. In some habitats, sequestration needs to be further researched. Natural England has produced a recent report with best estimate figures for many habitats, and these, alongside any equivalent figures from devolved nations, should be considered best evidence. Carbon sequestration estimates need to use standardised methods across different habitats to ensure accurate and comparable accounting and monitoring[5]. At the moment there is no standard protocol for collecting data on carbon store and fluxes across habitats.

 

Estimates of the carbon stored in vegetation tend to be more reliable than those of carbon stored in soil, and assessing reductions in greenhouse gas emissions is easier than assessing carbon storage and sequestration[6]. Carbon sequestration and emission reductions can be calculated through direct measurements of changes in the carbon stock in the soil or vegetation or modelling based on measurable proxies and emission factors (the former tends to be more accurate and expensive). A combination of the two can be used to improve the models’ reliability through limited direct measurements[7].

 

Duration and reliability of storage of carbon in NbS is also under researched. In general, carbon stored in vegetation biomass is stable on a decadal timescale, assuming forests are not destroyed. Use of wood for timber for building materials can also ensure long-term storage of carbon, although how much sequestered carbon is lost in the production of timber is poorly quantified. Carbon stored in peatlands is stable if the peatlands are kept in healthy conditions. Carbon stored in soil and marine sediments will most likely be affected by disturbance, including changes to land use or activities which break up the soil or sediments, such as ploughing or bottom trawling. Climate change, including heat, drought, excessive rainfall and increased wave action affect storage in many ecosystems (but wet peatlands are relatively robust to climate change and pollution).

 

There has been some successful, high-profile work done on restoring peatlands by organisations such as Moors for the Future, Yorkshire Peat Partnership, Natural England, Natural Resources Wales, NatureScot, the National Trust, the Wildlife Trusts and other organisations, businesses and consultancies, as well as universities and research institutes like the UK Centre for Ecology and Hydrology. It is essential that the resulting knowledge and experience is shared through events like the IUCN Peatland Programme, together with evidence from similar international projects. Due to the variety of peatland habitats in the UK, continued research is vital to ensure the best evidence based techniques are used to restore and manage all the country’s peatlands.

 

This work must include long-term monitoring of peatland GHG emissions. Consensus on the best way of doing this needs to be agreed by a government-supported group, and should include both ground-truthed landscape-scale systems, and smaller project-specific monitoring in-order to capitalise on novel restoration and management schemes.

 

Estimates of sequestration from marine habitats such as seagrass and saltmarsh tend to focus on sequestration through burial in sediment, rather than of biomass, because carbon is sequestered on much longer time scales in sediments. Saltmarsh has been studied as well as most habitats in the UK, although again, considerable variability exists between different surveys. No estimates of seagrass sequestration rates are available from UK studies, but carbon storage in UK seagrass beds is consistent with other areas, such as the US, where sequestration values exist. There is considerable uncertainty in sequestration in marine sediments. Photosynthesis does exceed respiration in the ocean, and it is likely that around 1% of primary production is ultimately sequestered[8]. Preliminary studies suggest kelp and other macroalgae may enhance marine sediment sequestration[9]. Fauna such as large predatory fish are thought to boost sequestration and zooplankton can have a variety of roles, depending on species, location, time of year and time of day [10]. The impacts of boosting primary productivity and of fishing also need considerably more research, but potentially primary productivity can be optimised to increase ocean sequestration rates with potential for greater sequestration by several percent of UK current emissions[11].

 

5. How should implementation of nature-based solutions be integrated with other government policies for landscapes and seascapes, for example, agricultural, forestry, and land-use planning policies?

The use of NbS should be integrated in the environmental, agricultural and forest policy. For example, the Environmental Land Management (ELM) schemes should be designed to enable an increasing implementation of NbS. In particular, the Landscape Recovery scheme, one of the three ELM schemes that are currently being piloted, can potentially play an important role in the delivery of NbS such as peatland and saltmarsh restoration projects and large-scale tree planting. It will be important that these schemes are designed to ensure permanence in the long-term, regular monitoring and sufficient advisory services to farmers. Recent policy developments, including the Tree Action Plan and the Peatland Action Plan, will also contribute to the implementation of NbS.

 

NbS should be prioritised at the landscape level, in particular in the context of the Local Nature Recovery Strategies (LNRS), i.e. the new system of spatial strategies for nature that local authorities will be required to design by the new Environment Bill. LNRS will underpin the Nature Recovery Network, which was established by the 25 Year Environment Plan to create or restore 500,000 hectares of wildlife habitats outside protected areas. These will provide a wide range of opportunities to design NbS that deliver multiple biodiversity, climate and socio-economic benefits.

 

Funding has also been made available from the UK Government, such as the Nature for Climate Fund, to support habitat improvements aimed at combatting the climate crisis, and there are specific peatland restoration funds targeted to each of the home countries.

 

Coordinating climate mitigation policies with other government policies will be very important to avoid perverse effects. For example, large-scale afforestation initiatives should avoid peatlands (including, whenever possible, shallow peats), productive agricultural lands and habitats of high conservation value like carbon- and species-rich permanent grasslands and heathlands, focussing instead on low biodiversity and low productivity grassland and urban areas. NbS should be designed within a spatially-explicit framework, in order to balance competing environmental objectives.

 

NbS to reduce greenhouse gas emissions or store carbon in vegetation and soils should be designated in order to maximise co-benefits in terms of biodiversity protection and ecosystem services. For example, rewetting peatland can help reduce flooding by slowing the flow of water during storm events and regulate catchment water flows during dry periods, while protecting their highly distinctive biodiversity, including rare species. Broadleaf woodlands of native tree species also offer considerably greater biodiversity benefits compared to conifer plantations, while offering similar (if slower to establish) carbon sequestration benefits.

 

Protection of habitats that deliver NbS is important to ensure carbon is not released to the atmosphere. Deforestation, draining or damaging peatlands or bottom trawling in carbon-rich marine sediments may result in considerable amounts of stored carbon being made biologically available and contributing to carbon emissions. The new 30 x 30 policy of protecting 30% of the UK marine and terrestrial areas by 2030 should ensure adequate protection is given to carbon stocks and carbon sequestering habitats, as well as focussing on protection of biodiversity.

 

9 September 2021

 


[1] Gregg, R., Elias, J.L., Alonso, I., Crosher, I.E., Muto, P. and Morecroft, M.D. (2021). Carbon storage and sequestration by habitat: a review of the evidence (second edition). Natural England Research Report NERR094. Natural England, York. [online] Available at: http://publications.naturalengland.org.uk/file/6726246198411264 (accessed: 07/09/2021).

[2] Parker, R., Benson, L., Graves, C., Kröger, S. and Vieira, R. (2021). Blue carbon stocks and accumulation analysis for Secretary of State (SoS) region: (2020) Cefas Project Report for Defra, 42pp. Cefas, Lowestoft, UK. [online] Available at: http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&ProjectID=20754 (accessed: 07/09/2021).

[3] Exclusive Economic Zone

[4] Overseas territories

[5] Gregg, R., Elias, J.L., Alonso, I., Crosher, I.E., Muto, P. and Morecroft, M.D. (2021). Carbon storage and sequestration by habitat: a review of the evidence (second edition). Natural England Research Report NERR094. Natural England, York. [online] Available at: http://publications.naturalengland.org.uk/file/6726246198411264 (accessed: 07/09/2021).

[6] COWI, Ecologic Institute and IEEP (2021) Technical Guidance Handbook - setting up and implementing result-based carbon farming mechanisms in the EU Report to the European Commission, DG Climate Action, under Contract No. CLIMA/C.3/ETU/2018/007. COWI, Kongens Lyngby.

[7] Ibid.

[8] Basu, S. and Mackey, K. R. (2018). Phytoplankton as key mediators of the biological carbon pump: Their responses to a changing climate. Sustainability, [online] 10: 869. Available at: https://doi.org/10.3390/su10030869.

[9] Krause-Jensen, D. and Duarte, C. (2016). Substantial role of macroalgae in marine carbon sequestration. Nature Geoscience, 9, pp.737–742.

[10] Saba, G.K., Burd, A.B., Dunne, J.P., Hernández-León, S., Martin, A.H., Rose, K.A., Salisbury, J., Steinberg, D.K., Trueman, C.N., Wilson, R.W. and Wilson, S.E. (2021). Toward a better understanding of fish-based contribution to ocean carbon flux. Limnology and Oceanography, [online] 66: 1639-1664. Available at: https://doi.org/10.1002/lno.11709.

Mayor, D.J., Gentleman, W.C. and Anderson, T.R. (2020). Ocean carbon sequestration: Particle fragmentation by copepods as a significant unrecognised factor? Explicitly representing the role of copepods in biogeochemical models may fundamentally improve understanding of future ocean carbon storage. BioEssays, [online] 42: 2000149. Available at: https://doi.org/10.1002/bies.202000149.

Mariani, G., Cheung, W.W., Lyet, A., Sala, E., Mayorga, J., Vele, L., Gaines, S.D., Dejean, T., Troussellier, M. and Mouillot, D. (2020). Let more big fish sink: Fisheries prevent blue carbon sequestration—half in unprofitable areas. Science Advances, [online] 6: eabb4848. Available at: https://doi.org/10.1126/sciadv.abb4848.

Luo, J.Y., Condon, R.H., Stock, C.A., Duarte, C.M., Lucas, C.H., Pitt, K.A. and Cowen, R.K. (2020). Gelatinous zooplankton‐mediated carbon flows in the global oceans: a data‐driven modeling study. Global Biogeochememistry Cycles, [online] 34: p.e2020GB006704. Available at: https://doi.org/10.1029/2020GB006704.

[11] Stafford, R., Boakes, Z., Hall, A. and Jones, G. (2021, PREPRINT) The role of predator removal by fishing on ocean carbon dynamics. Research Square. [online] Preprint available at: https://doi.org/10.21203/rs.3.rs-668946/v1.