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Hedgerows and the Fight Against Climate Change
Hedgerows have become a symbol of the British countryside. The patchwork blanket we each can see in our minds eye, defined by centuries of ancient rural farming practices. They are also one of our great allies as we face the momentous challenge to reduce and revert our carbon footprint as a country.
Hedgerows were once a vital landscape feature for farmers, providing a number of services beyond simply determining the boundary of land ownership. Dense, unbroken hedgerows freed up time and supplemented resources; a way to keep your own animals in and your neighbours out without your constant attention, to provide additional food and shelter for your livestock, regular firewood, as well as nuts and berries to supplement and add variety to your diet.
Alongside these benefits to humans, hedgerows are crucially important for the wildlife that has learnt to live in and rely on the farming landscape. Hedgerows provide a network of food, shelter and means of navigation for so many animals, from insects, including pollinators, and birds to small mammals. With over 70% of the land in the UK being used for agriculture in one way or another [1], it comes with little surprise that hedgerows are cited as one of the UK’s largest priority habitats [2]. Over 2,070 species were found in a single stretch of hedgerow in Devon [3]. Hedges and their associated features can provide the niches required for a diverse range of species including a number of threatened and endangered species such as the hedgehog, hazel dormouse, turtle dove, great crested newt and many of our UK bats.
Ripped out, abandoned or trimmed within an inch of their lives, some records suggest that hedgerows may have suffered a dramatic loss of up to 50% since WW2 [4]. This is the equivalent length of our entire UK road system, and some. The Countryside Survey of 2007, commissioned by nine government funded bodies, found that only 50% of the remaining hedgerows in England were in favourable condition, a figure even lower in Wales and Scotland [5]. Where wildlife once thrived, it is now a common sight to see hedges with holes in, bare at the base or entirely separated into hedge islands, providing no functional use at all.
And this impact goes way further than that on wildlife. Simply put, as plants grow, they convert the carbon in the air into the sugars they use to grow. This makes plants one of our great allies as we face the momentous challenge to reduce and revert our carbon footprint as a country. Hedges in poor condition are slowly dying, far from growing at rates close to their full potential each year. This means that they are not removing the annual quantity of carbon from the air that they could be.
The Climate Change Committee produced a report in 2019 highlighting the need to restore and replant hedges as one of the many ways in which we must address our swelling carbon debt. The report states that a 40% increase in hedgerows by 2050 (#40by50) is required to achieve the 2050 target of net zero for the UK [6].
Natural England produced a report in 2020, defining the favourable conservation status (FCS) of hedgerows, where the FCS is the minimum threshold at which habitats and species can be considered to be thriving. The report outlines the requirement of an additional 335,000 km to be planted, a 60% increase in hedgerows in England alone. Furthermore, they state that existing hedges, of which 50% are in unfavourable condition, need to be restored to a minimum of 95% in favourable condition [7].
A healthy hedgerow will grow every year, putting on woody material which can be harvested on a trimming cycle to supply a sustainable wood fuel source. Depending on factors such as the plant age and species, the weather conditions, the soil type, previous land use, height and width, the management routine and so on, the amount any section of hedgerow grows and thus stores carbon each year will vary. However, preliminary research has shown that hedges may have the potential to remove somewhere in the range of 0.5 tonnes to 5 tonnes of carbon per hectare per year.[8][9]
Not only does this provide an incredibly important mechanism for carbon storage, but restoring and replanting hedgerows will also positively impact biodiversity loss. Neighbouring habitats will also see increased biodiversity as a result of the improved landscape connectivity. [10]
So the humble hedgerow, is in fact an incredible tool not just for our countryside, but to the survival of our planet as a whole. And the great thing is, we all have the power to make a contribution. From the hedgerows in your garden to those you see all around you, in your village, town, city or surrounding countryside. Think about what, who and where you can influence – your local council, your local school, community groups and the local farming community. Our CPRE Hampshire hedgerow hub has lots of resources you can turn to help inform and educate – take a look for yourself and spread the word. Hedgerows are real countryside heroes.
The science
Taking carbon out of the air: Photosynthesis is the process in which plants make sugar to grow. They absorb carbon dioxide (CO2) into their leaves from the air through tiny holes that they can open and close, called stomata. Chlorophyll, the chemical that makes leaves green, helps the leaves absorb light energy from the sun. The CO2 from the air and the water drawn up from the roots react together using the from the sun to form sugar, glucose. Sugars are what we call organic compounds and this means they contain carbon. The carbon from the air, in the form of the CO2, has been transformed into the precursor of the building blocks of plants (glucose, C6H12O6). These sugar molecules are then further converted to cellulose and starch, more useful materials for growing leaves and woody material where the carbon then stays (until the branch or leaves fall off, or the plant dies).
Putting carbon into the ground: As well as for growth, some of these sugars are exuded out of the roots, into the soil, feeding the microorganisms that live there. These sugars also feed their fungal partners, and in exchange receive essential minerals that their roots cannot reach. Using these sugars, these fungi develop their networks in the soil – built from the carbon in the air that we emit.
When the leaves fall off the shrubs and trees in our hedgerows each year, they are broken down and rotted into soil by the fungi and microorganisms that live there, and much of the carbon that the leaves are made up of remains in the soil. With plants growing above ground, the soil can fulfil its role as a carbon store. Much of our agricultural soils have been depleted in carbon through intensive agricultural practices and offer huge potential as a natural carbon store.
References:
[1] Savills (2019) Current agricultural land use in the UK. Available at: Savills UK | Current agricultural land use in the UK (Accessed: 31 May 2022).
[2] BRIG ed. Ant Maddock. (2008) UK Biodiversity Action Plan: Priority Habitat Descriptions.
[3] Staley, J.T.; Wolton, R.; Norton, L. (2020) Definition of Favourable Conservation Status for Hedgerows. Natural England.
[4] Wright, J. (2017) A Natural History of the Hedgerow: Ditches, Dykes and Dry Stone Walls. Profile.
[5] Brown, M.J.; Bunce, R.G.H.; Carey, P.D.; Chandler, K.; Crowe, A.; Maskell, L.C.; Norton, L.R.; Scott, R.J.; Scott, W.A.; Smart, S.M.; Stuart, R.C.; Wood, C.M.; Wright, S.M. (2014) Countryside Survey 2007 estimates of linear feature lengths in Great Britain. NERC Environmental Information Data Centre.
[6] Stark, C.; Thompson, M. et al. (2019) Net Zero: The UK’s contribution to stopping global warming. The Committee on Climate Change.
[7] Staley, J.T.; Wolton, R.; Norton, L. (2020) Definition of Favourable Conservation Status for Hedgerows. Natural England.
[8] Drexler, S.; Gensior, A.; Don, A. (2021) Carbon sequestration in hedgerow biomass and soil in the temperate climate zone. Regional Environmental Change.
[9] Black, K.; Green, S.; Mullooley, G.; Poveda, A. (2014) Carbon Sequestration by Hedgerows in the Irish Landscape. Environmental Protection Agency.
[10] Staley, J.T.; Wolton, R.; Norton, L. (2020) Definition of Favourable Conservation Status for Hedgerows. Natural England.
