Dr Ana Queiros, Plymouth Marine Laboratory, Professor Nathalie Seddon and Ms Alison Smith, University of Oxford – Written evidence (NSD0020)


Written evidence submitted by Professor Nathalie Seddon and Alison Smith of the Nature-based Solutions Initiative[1], Department of Biology and Environmental Change Institute, University of Oxford; and Dr Ana Queirós, Plymouth Marine Laboratory[2].


Q1. Definitions: Nature-based Solutions (NbS) are defined as actions that involve the protection, restoration, or management of natural and semi-natural ecosystems; sustainable management of farmland and fisheries; or the creation of new green infrastructure in and around built-up areas[3]. They are actions that support biodiversity (i.e. the diversity of life from genes to ecosystems) and are designed and implemented by or in partnership with local communities to deliver local benefits. They do not include i) bioenergy carbon capture and storage (BECCs); ii) tree-planting on naturally treeless landscapes (e.g. ancient grasslands and peat bogs); or iii) plantations of non-native tree species. These practices, though they involve biological as opposed to technological carbon sequestration, erode rather than support biodiversity. Non-native plantations can be high-risk, impermanent carbon stores as they are more vulnerable to climate change impacts (such as fire and the spread of new pathogens) than biodiverse, intact native ecosystems.[4],[5] Scale: Globally, the total cost-effective mitigation potential of NbS on land is estimated as around 10 Gt CO2 /yr (11 GT CO2-equivalent). This would reduce global warming by around 0.1°C if warming peaks mid-century at 1.5°C since pre-industrial times or around 0.3°C if warming peaks around 2075 at 2°C.[6] Although this is a significant contribution, it shows that most of the required GHG reduction must come from the rapid phase-out of fossil fuels. Furthermore, unless fossil fuel emissions are drastically reduced, the resultant warming (and associated increased risk of heat stress, droughts, fires and diseases limiting plant growth) will turn parts of the biosphere from a sink into a net source of GHGs[7].


a) NbS with the highest GHG mitigation potentials in the UK: (i) Protecting the 16,231 Mt CO2e, of carbon stored in existing natural ecosystems, equivalent to 35 years of total UK GHG emissions[8] (ii) Restoring degraded peatlands, which currently emit 21.3 MtCO2e /year, turning the land-use and forestry sector from a carbon sink of –9.8 MtCO2e to a net source of 11.5 MtCO2e.[9] (iii) Better management of farmland through nature-based methods that increase soil carbon, reduce the use of synthetic fertilisers and increase tree and hedgerow biomass. Agriculture currently produces 10% of UK emissions, but this could be cut by 45% if these NbS are accompanied by a shift to a more plant-based diet.[10] This includes restoration of low-input species-rich grassland. Similarly, at the global level, 40% of the total mitigation potential of NbS is achievable through more sustainable, nature-based management of croplands and timberlands (around 5 GT CO2/yr)6. (iv) Restoring native woodland can play a useful but more limited role, with cumulative additional climate change mitigation of 44-71 Mt CO2e by 2030 (10-16% of 2019 emissions). (v) Marine and coastal areas offer significant (though sparsely quantified) mitigation potential in soft-sediment beds, seagrass, saltmarsh and macroalgae (kelp forests). UK coastal and shelf marine soft-sediments could sequester c. 77Mt C/yr.[11],[12] Per unit of area, these fluxes are c.25% of those observed in seagrass and saltmarsh habitats, but the area is 130 times larger13. Deep sediments (>200m) could also have high sequestration rates, but data are lacking. For more detail on the climate change mitigation potential of NbS in the UK see recent report by the BES[13].


Most relevant NbS for the UK, to help meet climate change mitigation targets whilst also supporting climate change adaptation and biodiversity/nature recovery goals[14]: (i) Protection of existing woodlands, hedgerows, trees, kelp forests, peatland and semi-natural grassland through stronger planning policy. This would require closing the loophole in the NPPF that allows destruction of habitats (including ancient woodlands, which store large amounts of carbon) for major infrastructure projects. (ii) Peatland protection should include banning the production and sale of horticultural peat both for amateur and professional use. The current ban on planting trees on ‘deep’ peat (over 50cm depth in Scotland or 40cm in England) should be extended to include all depths of peat and organic soils, as recent evidence shows that even planting on shallow peat or peaty soils can cause net losses of carbon[15]. This would preclude planting trees on heather moorland; a practice that is ongoing in Scotland. (iii) Kelp forest protection should include reducing overharvesting of kelp (e.g. for pharmaceutical products, bioplastics or biofuel). (iv) Restoration and connection of native woodlands, hedgerows, grasslands, heathlands, peatlands (including lowland peat i.e. fenland peat drained for agriculture), wetlands, saltmarshes, kelp forests and seagrass meadows. (v) Reforestation of low-quality farmland on mineral soils with mixed native species, especially on slopes in mid-catchments. (vi) Reversion of low-quality arable land to permanent grassland, especially on slopes or on floodplains. This can also reduce soil erosion and water pollution from agricultural runoff. (vii) Agroforestry, silvo-arable and silvo-pasture increases carbon storage above and below ground, whilst also providing shade and shelter for livestock, important for climate change adaptation. (viii) Regenerative agriculture that stores more carbon in soil, e.g. no-till or low till farming, use of cover crops, addition of organic matter to the soil, buffer strips or contour hedgerows to reduce soil erosion, and other soil-water conservation methods. (ix) Urban green infrastructure (parks, city forests and parks, street trees, green roofs, sustainable drainage) – especially for climate change adaptation (urban cooling and flood protection)[16].


b) Area required. For land-based NbS, protecting existing habitats, restoring degraded peat and managing farmland more sustainably offers the potential for carbon mitigation without a change in land-use. In contrast, other options such as planting trees (or non-NbS options such as BECCS) could result in trade-offs with land needed for food production. Agroforestry involves planting trees on pasture or amongst crops while maintaining or even enhancing food production, as it can support resilience to climate change. For marine NbS, it is important to protect the vast amounts of carbon stored in shelf sediments, which is adversely affected by extractive uses of the seabed (e.g. trawling, aggregate extraction)8. In particular, bottom trawling represents 90% of the footprint of physical abrasion to the seabed within the UK EEZ. Further research is needed to determine the area that should be protected, building on methodological developments and analyses from the UK’s Marine Ecosystems Research Programme and the Shelf Seas Biogeochemistry Programme, funded by NERC and DEFRA.


c) NbS vs other decarbonisation options. Non-nature-based approaches to GHG removal can have adverse impacts: e.g. enhanced weathering involves mining, milling and transporting large quantities of rock and BECCS uses large areas of land for monoculture plantations of energy crops; Direct Air Capture, meanwhile, is currently energy and materials intensive[17]. Further research is needed to assess the extent to which these approaches can be taken to scale without compromising social and environmental goals. In contrast, well-designed and properly implemented NbS can bring a wide range of co-benefits: they can support biodiversity, provide health benefits and reduce climate change impacts.[18] For example, there is good evidence that NbS can i) reduce the exposure of communities, infrastructure and agricultural land to extreme events (e.g. flooding or heatwaves); ii) limit sensitivity to climate change (e.g. by supporting diverse alternative sources of income and food during times of shortage); and iii) increase capacity to deal with future shocks and changes, because social capital, as well as natural capital, is built through the process of protecting, restoring and sustainably managing the natural world[19].


Q2. Scientific uncertainties. The current evidence base focuses on the carbon impacts of tree-planting and peatland restoration. It is currently very difficult to estimate the carbon impacts of other types of NbS due to a lack of data. More funding is needed for establishing and monitoring a wide range of NbS, including grassland and heathland restoration, natural regeneration of woodland / rewilding, agroforestry and other nature-based agriculture options. More research is also needed for marine NbS - not only seagrass, mangrove and saltmarsh, but also the larger flows of carbon between different ocean components, such as when carbon is fixed into living biomass (e.g. macroalgae, plankton) in one area of the ocean and then flows as particulate or dissolved materials into other areas where it may become sequestered in the seabed[20]. Large uncertainty about the size of these carbon flows between ecosystem components currently prevents their inclusion in carbon accounting.[21] Accounting on both land and sea also needs to take into account the impacts of climate change on the biosphere.


Q3. Frameworks. Current frameworks for regulating and financing NbS focus almost exclusively on tree-planting and peatland restoration for climate mitigation, and tend to neglect other NbS and non-carbon impacts. This has led to problems with planting of non-native trees damaging other biodiverse and carbon-rich habitats such as species-rich grassland.2 To help address these problems and promote synergy between climate and biodiversity goals, a group of conservation, development and research organisations has developed four evidence-based guidelines for policymakers (www.nbsguidelines.info), which are intended to complement the more detailed IUCN Global Standard for Nature-based Solutions[22]:

1)    NbS for climate mitigation are not a substitute for decarbonising the economy;

2)    NbS should be supported in a wide range of ecosystems, including semi-natural grasslands, floodplain meadows, heathland, scrub, native woodland, wetlands, saltmarshes and coastal and marine habitats (kelp, seagrass, saltmarsh, dunes);

3)    NbS should be designed and implemented with and for local communities;

4)    NbS should be explicitly designed to deliver benefits for biodiversity.


Guideline 1 is particularly relevant for regulation of carbon offsetting markets. NbS should not be seen as a means of achieving cheap offsetting in corporate mitigation policies; this distracts from the urgent need for rapid decarbonisation (Q1). Yet high emitting industries (airports, airlines, and oil and gas companies) are proposing to use NbS to offset their emissions, with some claiming “carbon neutrality”, without cutting emissions. It is therefore critical to hold to account those claiming NbS carbon offsets to ensure they have ambitious, credible and verifiable plans to rapidly phase out use of fossil fuels. The Oxford Principles for Offsetting[23] and the new Corporate Guidelines on Natural Climate Solutions[24] developed by the Natural Climate Solutions Alliance convened by the World Economic Forum and World Business Council for Sustainable Development partly address this, but both need refining to ensure the long term integrity of the offsets claimed.


Q4. Stakeholders. To ensure that NbS deliver genuine benefits for biodiversity, key stakeholders include organisations supporting nature conservation and recovery, as well as environmental and landscape quality across a wide range of UK species and habitats, incl. Natural England, JNCC, CIEEM, CIWEM, Local Nature Partnerships, the Wildlife Trusts, Freshwater Habitats Trust, Floodplain Meadows Partnership, Woodland Trust, National Trust, RSPB, WWF-UK, Buglife, Plantlife, Butterfly Conservation, Amphibian and Reptile Society, UNESCO Man and Biosphere Reserves, AONBs and CPRE. Local communities should also be involved in design, implementation, monitoring and evaluation of NbS in their areas.


Q5. Integration. Scaling up NbS (especially the restoration and protection of key ecosystems) would benefit from policies that (a) protect all natural habitats in the planning system; (b) connect habitats across landscapes in line with the emerging Nature Recovery Networks; (c) build NbS into new developments as green infrastructure (e.g. sustainable drainage systems in new developments); (d) use agriculture payments (e.g. the Environmental Land Management Scheme in England) to support actions that benefit both climate and biodiversity, including options that are currently not supported such as agro-forestry and organic or regenerative farming; (e) synergise where possible with emerging EU legislation. Current policies do not place sufficient emphasis on ensuring that NbS deliver biodiversity benefits, and fail to optimise the wider benefits for climate adaptation, health and well-being. For example, there is lack of financial and policy support for rewilding and natural regeneration of woodland, which can deliver highly resilient, biodiverse and carbon-rich landscapes; as well as biodiverse green roofs, which have multiple benefits for climate adaptation; agroforestry; and multifunctional sustainable drainage systems with benefits for biodiversity and people.13


Q6. Planning and monitoring. The four NbS guidelines (Q3) are designed to inform the planning, implementation and evaluation of NbS projects. Practitioners should set goals and quantitative targets relating to each guideline, monitor progress towards these targets using comprehensive metrics, and use adaptive management to improve outcomes. In addition to verifying the carbon reduction credentials of NbS investors (guideline 1, Q3) it is vital to develop clear evidence-based metrics to ensure sustainability and allow investors to demonstrate and verify the carbon, biodiversity and social benefits of a wide range NbS in rural and urban environments (guideline 2). There are tools available to estimate the carbon benefits of tree planting and, to some extent, peatland restoration, but there are major data gaps for other NbS options such as restoring natural grassland (including floodplain meadows), heathland; saltmarsh, seagrass or kelp beds, agroforestry, and natural regeneration (as opposed to planting) of native woodland/scrub/grassland mosaics. In addition, biodiversity and social impacts (guidelines 3 and 4) are rarely monitored. For example, often there is an implicit assumption that any tree-planting will benefit carbon, biodiversity and local people, while impacts can be either positive or negative depending on the species mix and the current land use.


10 September 2021



[1] www.naturebasedsolutionsinitiative.org

[2] https://www.pml.ac.uk/

[3] Cohen-Shacham et al. (2016) 10.2305/IUCN.CH.2016.13.en

[4] Seddon, Smith et al. (2021) Getting the message right on nature-based solutions to climate change. Global Change Biology: https://onlinelibrary.wiley.com/doi/10.1111/gcb.15513

[5] Seddon, Chausson et al. (2020) Understanding the value and limits of nature-based solutions to climate change. Phil Trans Roy Soc: https://doi.org/10.1098/rstb.2019.0120

[6] Girardin, C. et al. (2021). Nature-based solutions can help cool the planet—If we act now. Nature, 593, 191–194.

[7] Anderegg, W. R. et al. (2020). Climate-driven risks to the climate mitigation potential of forests. Science, 368: https://www.science.org/lookup/doi/10.1126/science.aaz7005

[8] Total UK GHG emissions were 454.8 Mt CO2e in 2019, https://www.gov.uk/government/collections/final-uk-greenhouse-gas-emissions-national-statistics

[9] RSPB-WWF-Oxford-Aberdeen (2020) Role of Nature in a UK NDC.

[10] Poux, X. & Aubert, P-M. (2018) An agro-ecological Europe: a desirable, credible option to address food and environmental challenges. IDDRI Issue Report.

[11] Queirós, A. M. et al. (2019) Connected macroalgal‐sediment systems: blue carbon and food webs in the deep coastal ocean. Ecological Monographs 89, no. 3 (2019): e01366. 

[12] Legge, O. et al. (2020) Carbon on the northwest European shelf: Contemporary budget and future influences. Frontiers in Marine Science 7 (2020): 143.

[13] Stafford, R., Chamberlain, B., Clavey, L., Gillingham, P.K., McKain, S., Morecroft, M.D., Morrison-Bell, C. and Watts, O. (Eds.) Nature-based Solutions for Climate Change in the UK: A Report by the British Ecological Society. London.

[14] RSPB-WWF-Oxford-Aberdeen (2020) Role of Nature in a UK NDC.

[15] Friggens et al. (2020) Tree planting in organic soils does not result in net carbon sequestration on decadal timescales. Global Change Biology 26, 5178–5188.

[16] Research by the NATURVATION project demonstrates that NbS can address climate adaptation and mitigation needs for cities, while also contributing to biodiversity conservation and enabling communities to access nature (https://naturvation.eu/assessment/maps).

[17] Chatterjee, S., & Huang, K. W. (2020). Unrealistic energy and materials requirement for direct air capture in deep mitigation pathways. Nature Communications, 11, 1-3.

[18] Smith, A. and Chausson, A. (2021). Nature-based Solutions in UK Climate Adaptation Policy. Report for WWF and RSPB by the Nature-based Solutions Initiative, University of Oxford.

[19] Chausson, A., Turner, C. B. et al. (2020). Mapping the effectiveness of Nature-based Solutions for climate change adaptation. Global Change Biology: https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.15310

[20] Smale, D. A. et al. (2018). Appreciating interconnectivity between habitats is key to blue carbon management. Frontiers in Ecology and the Environment, 16, 71-73.

[21] Krause-Jensen, D. et al. (2018). Sequestration of macroalgal carbon: the elephant in the Blue Carbon room. Biology Letters: https://doi.org/10.1098/rsbl.2018.0236

[22] IUCN. (2020). Guidance for using the IUCN global standard for nature-based solutions (1st ed.).

[23] https://www.smithschool.ox.ac.uk/publications/reports/Oxford-Offsetting-Principles-2020.pdf

[24] http://www3.weforum.org/docs/WEF_NCSA_NCS_for_Corporates_2021.pdf