Carbon Storage and Sequestration by Habitat: a Review of the Evidence (Second Edition)
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Natural England Research Report NERR094 Carbon storage and sequestration by habitat: a review of the evidence (second edition) www.gov.uk/natural-england Natural England Research Report NERR094 Carbon storage and sequestration by habitat: a review of the evidence (second edition) Ruth Gregg, Jessica Elias, Isabel Alonso, Ian Crosher, Paul Muto and Mike Morecroft 20th April 2021 This report is published by Natural England under the pen Government Licence - OGLv3.0 for public sector information. You are encouraged to use, and reuse, information subject to certain conditions. For details of the licence visit Copyright. Natural England photographs are only available for non commercial purposes. If any other information such as maps or data cannot be used commercially this will be made clear within the report. ISBN 978-1-78354-732-6 © Natural England 2021 Project details This report should be cited as: R Gregg, J. L. Elias, I Alonso, I.E. Crosher and P Muto and M.D. Morecroft (2021) Carbon storage and sequestration by habitat: a review of the evidence (second edition) Natural England Research Report NERR094. Natural England, York. Project manager Natural England Project Manager: Dr. Ruth Gregg [email protected] Acknowledgements We are grateful to the following external experts who reviewed and provided comments on the report, or specific chapters within it: Dr. Rob Field (RSPB), Dr. Doug Warner (University of Hertfordshire), Prof. Fred Worrall (Durham University), Dr. Mark Broadmeadow (Forestry Commission), Dr. James Morison (Forest Research), Dr. Jo-Anne Pitt, Dr. Mark Diamond, Dr. Glenn Maas, Dr. Judy England, Alice Hiley, Dr Mark Bourn (Environment Agency), Dr. Ruth Parker and Lisa Benson (Cefas), Prof. Chris Evans (UKCEH). We are also grateful to Samantha Broadmeadow (Forest Research) who produced Figures 2.4 and 2.5; and Dr Amanda Thomson and Dr Hannah Clilverd for their assistance regarding the 2021 update to the UK Peatland GHG Emissions Inventory. We are grateful to the following (current and former) Natural England staff who provided input, comments and feedback on report drafts: Nigel Pilling, Emma Goldberg, Marion Bryant, Steve Peel, Andy Cole, Richard Jefferson, David Whiting, Alistair Crowle, Deborah Land, Dave Glaves, Iain Diack, Chris Mainstone, Ruth Hall, Simon Duffield, Ginny Swaile, Margaret Street, Katrin Bohn, Sue Rees, Hazel Selley, Victoria Copley, Alexandra Fawcett, Theresa Redding, Jakub Olewski and Sarah Taylor. ii Natural England Research Report NERR094 Executive Summary Report background Achieving ‘net zero’ greenhouse gas (GHG) emissions by 2050 is a statutory requirement for the UK and England. It will require major changes in the way we manage the land, coast, and sea, alongside decarbonisation of the energy, transport and other sectors. The natural environment can play a vital role in tackling the climate crisis as healthy ecosystems take up and store a significant amount of carbon in soils, sediments and vegetation. Alongside many other negative impacts, the destruction and degradation of natural habitats has resulted in the direct loss of carbon stored within them. Restoring natural systems can start to reverse this damage at the same time as supporting and enhancing biodiversity, alongside delivering co-benefits for climate change adaptation, soil health, water management and society. This Natural England Research Report is designed to clearly set out the evidence for how restoration and good management of habitats can contribute to climate change mitigation. In this report, we review the scientific evidence base relating to carbon storage and sequestration by semi-natural habitats, in relation to their condition and/or management. This new report updates and expands previous work by Natural England on ‘Carbon storage by habitat’ published in 20121. We cover terrestrial, coastal and marine habitats, and the freshwater systems that connect them, in order to quantify their relative benefits for carbon management. We set out to: • Review the available evidence and summarise the carbon storage and sequestration rates of different semi-natural habitats with an indication of the range of values and the degree of confidence we can place in them. • Facilitate the comparison of carbon storage and sequestration rates between semi-natural habitats. • Apply evidence to England. Our main focus has been on evidence gathered on British ecosystems, but we have also included studies from other regions, particularly north west Europe, where they are relevant and helpful. • Identify key evidence gaps in order to highlight where there is need for future research to support land use and land management decisions for carbon. • Provide those working in land management, conservation and policy with relevant information required to underpin decisions relating carbon in semi-natural habitats. 1 Carbon storage by habitat: Review of the evidence of the impacts of management decisions and condition of carbon stores and sources (NERR043) iii Nature-based solutions Climate change and biodiversity loss are inextricably linked and need to be addressed in an integrated way. Nature-based solutions (NbS) is a broad concept which describes how protecting, restoring and managing natural systems can solve societal problems. A widely used definition is that of the International Union for the Conservation of Nature (IUCN): nature-based solutions are “actions to protect, sustainably manage, and restore natural or modified ecosystems that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits”. Figure 1 Examples of relationships between nature-based solutions, nature recovery and net zero The most effective NbS for climate change mitigation are often those based on habitat restoration and creation (figure 1), as land use change from a degraded habitat to a functioning, resilient one offers the greatest potential in capturing carbon dioxide from the atmosphere. The protection of existing habitats is also vital, as their biodiversity and carbon stocks may have taken centuries to millennia to become established and are quickly lost if disturbed. Carbon storage and sequestration by habitat – key messages from this report Since the last Natural England report on carbon storage and sequestration by habitats in 2012, both science and policy have increasingly recognised the importance of natural ecosystems in climate change mitigation and their wider benefits for society. Comparing across habitats is complicated, as there is no standard protocol for collecting carbon and flux data, and habitats and land use are often looked at in isolation. Broad habitats in the carbon reporting literature are typically aggregated together, but in reality comprise a range of different systems, the attributes of which may affect carbon cycling (for example fens include a variety of types in different hydrological conditions and heath includes both dry and wet heath). As a result, reviews of this kind are rarely undertaken but are necessary to understand how best to target and prioritise habitat creation, restoration and land iv Natural England Research Report NERR094 management to mitigate climate change. To facilitate this approach, we conducted in-depth literature reviews across a range of habitats relevant to conservation in England, set out in the following habitat chapters. Figures 2 and 3 present a high-level overview of carbon storage and sequestration by different habitats. Key messages are identified but it should be noted that a huge range of different information underlies this overview, which is set out in the chapters. Chapter 2: Woodland, trees and scrub – The largest carbon sequestration rates amongst semi- natural habitats are in woodlands. Native broadleaved woodlands are reliable carbon sinks that continue to take up carbon over centuries with benefits for biodiversity and other ecosystem services, although the rate varies greatly with tree species and age and is strongly influenced by soils and climate. Sequestration rates decline over time, but old woodlands are substantial and important carbon stores. Although woodland management may be important for a range of reasons, it is not essential to maintain carbon sequestration. Native woodland managed with a minimum intervention approach can be an effective climate change mitigation measure. Timber production can have benefits for climate change mitigation where wood products store carbon for the long-term, or replace more fossil fuel intensive materials and fuels; and can be produced in ways that support biodiversity, such as using native tree species and management of rides and forest edges. However, non-native species of tree generally support lower levels of biodiversity and plantations on peatlands have led both to the loss of biodiversity and carbon. Hedgerows, orchards and other trees outside woodland can also sequester and store carbon as well as providing other benefits within an agricultural and biodiversity context. Chapter 3: Open habitats and farmland – Open habitats such heathlands and semi-natural grasslands sequester and store more carbon than modern agricultural landscapes but typically store less carbon than peatlands, saltmarsh and established woodlands. They also sequester less carbon than woodlands, as they do not accumulate woody matter. Vegetation may also be managed by grazing or cutting, representing a loss of carbon from the system. Agricultural land use on peat soils gives rise to extremely