The Carbon Underfoot: How a Rewilded Garden Compares to a Conventional One

It's a lovely idea, and you'll see it repeated everywhere: let your garden go wild and it becomes a mighty sponge for carbon, quietly doing its bit against climate change. Like most lovely ideas about the environment, it's partly true, partly oversold, and a great deal more interesting once you look at what's actually going on in the soil and the stems.

So let's do that honestly. How does a rewilded garden compare to a conventional one when it comes to carbon and where does the real difference lie? The short version: it's less about your wild garden being a spectacular carbon store, and more about three quieter truths; the standing carbon in wood, the living carbon in undisturbed soil, and the emissions a conventional garden quietly racks up that a wild one simply avoids. That last one is the surprise.

What a conventional garden actually does with carbon

Picture the classic tidy plot: a close-mown lawn, some bedding, a patio, a fence, perhaps a lone ornamental shrub. Where is the carbon?

Above ground, almost nowhere. Mown grass holds only around a tonne of carbon per hectare in living matter; a rounding error next to what wood can store. Every time you mow, you cut the plants back before they can build any lasting structure, so the living, breathing carbon store of a lawn is vanishingly thin.

The soil beneath a lawn is a different matter; grassland soils can and do hold carbon, and UK research (more on this below) shows garden soils are often richer than we assume. But here's the catch that the "wild gardens save the planet" version leaves out: whether a lawn is a net carbon sink or a net carbon source depends almost entirely on how you treat it. In a landmark 2010 study in Geophysical Research Letters, Townsend-Small and Czimczik found that ornamental turf stores carbon only when managed 'gently' and that intensively managed lawns, with frequent mowing, irrigation and synthetic fertiliser, can tip over into being net emitters. Later work agrees: a 2023 synthesis found the carbon footprint of an intensively managed lawn can reach around 44 tonnes of carbon per hectare over two decades, exceeding the roughly 28 tonnes it might sequester in the same period. In other words, the harder you work a conventional lawn, the more likely it is to cost the climate rather than help it.

This all points us straight to the nuances of the 'hidden ledger' but first, the good news about where a wild garden genuinely pulls ahead.

Where the rewilded garden wins: wood

The single biggest carbon difference between a wild garden and a conventional one is woody biomass; trees, shrubs and a proper hedge. This is carbon you can see, and it accumulates year on year.

The numbers are in a different league from grass. Around 15–30% of a tree, by volume, is carbon, locked into its trunk, branches and roots for as long as the tree stands. The Woodland Trust estimates that a hectare of native broadleaf woodland stores something like 300–350 tonnes of carbon over a century, against a lawn's single tonne above ground. Obviously your garden is not a hectare of woodland, but the principle scales all the way down: a single well-chosen tree, a dense mixed hedge left to grow tall and wide rather than clipped hard, a thicket of shrubs; each is a standing carbon store that a patio and a fence panel can never be. Research on managed hedges bears this out, finding that simply letting a hedge grow wider and taller measurably increases the carbon held in its woody biomass.

This is the most powerful, most visible lever an ordinary gardener has. Plant woody things, and let them get big.

Where it wins more quietly: living soil

Soil is where most of the world's terrestrial carbon actually lives; more than in all vegetation and the atmosphere combined, and it's where a rewilded garden does its subtlest work.

Encouragingly, gardens start from a good place. Research led by Jill Edmondson at the University of Sheffield, mapping the soils of Leicester, found that urban soils store considerably more organic carbon than the surrounding farmland, and that domestic gardens in particular held richer soil carbon than other green spaces, with garden soils averaging more than double the value national inventories had assumed. Crucially for us, her work also found that soils under trees and shrubs were in better physical condition than those under lawn, and that planting trees can enhance the carbon stored in a garden's soil.

The rewilding advantage here is mostly about what you stop doing. Soil carbon is built by living roots and returning organic matter, and it's lost through disturbance. Every time soil is dug over, tilled or left bare, it exhales carbon it had banked. A rewilded garden; permanently planted, mulched rather than dug, its ground always covered and its roots always growing, holds onto that carbon and slowly adds to it. A conventional garden that's regularly dug, kept bare between plantings and stripped of its "mess" is forever breaking the bank open.

The hidden ledger: the emissions a wild garden never makes

Here's the part that genuinely surprises people, and it's where a rewilded garden may do the climate the most good of all; not by storing dramatic amounts of carbon, but by not emitting what a conventional garden does.

Run down the hidden carbon costs of the tidy plot:

• The mower. Most garden mowers burn petrol, and that fuel use alone has been estimated at around a quarter of the carbon stored in an ornamental lawn. Put the mower away for much of the year, as a wilder garden lets you, and that cost largely disappears.

• The fertiliser. This is the big one. Synthetic nitrogen fertiliser drives emissions of nitrous oxide; a greenhouse gas with roughly 298 times the warming power of carbon dioxide. A fed, "perfect" lawn can emit enough nitrous oxide to cancel out much of the carbon it stores. A wild garden, fed by its own leaf litter and compost, emits none of it.

• The peat. As we've covered elsewhere, peat compost is dug from Britain's single largest carbon store; peatlands hold more carbon than the forests of the UK, France and Germany combined, releasing that carbon the moment it's disturbed. Going peat-free, as a rewilder naturally does, avoids one of gardening's largest and most needless emissions.

• The hard landscaping and the hose. Concrete, imported stone and resin all carry heavy "embodied" emissions from their manufacture, and mains water has an energy cost of its own. A garden that leans on planting rather than paving, and on rainfall rather than irrigation, quietly sidesteps both.

Add it up and the picture inverts the usual story. The conventional garden isn't carbon-neutral with a wild garden pulling ahead on sequestration; the conventional garden often carries a real carbon cost, and much of rewilding's benefit is simply refusing to pay it.

An honest reckoning

In absolute terms, the carbon a single garden stores or saves is modest; this is not a reason to fly less guilt-free. The value is collective: with more than twenty million gardens in the UK, small per-garden differences add up to a genuinely large area of land managed well or badly. Your garden matters most as one of millions.

Sequestration isn't permanent, and it isn't infinite. Soils and trees don't store carbon forever. Soil carbon eventually saturates; a tree that burns, rots or is felled gives its carbon back. Storing carbon in a garden buys time and does real good, but it's a living, reversible store, not a vault.

Carbon is the wrong reason to do this, or at least, not the main one. The finest thing about a rewilded garden was never its carbon maths. It's the hedgehogs and the goldfinches, and the dragon flies; the cooler air on a hot day, the rain soaking away instead of flooding the drain, the sheer aliveness of the place. Carbon is one thread in that web, not the whole cloth. Happily, almost everything that makes a garden better at holding carbon - more wood, undisturbed living soil, fewer chemicals, less concrete - is exactly what makes it better for everything else too.

The real difference, in a sentence

A conventional garden tends to store little living carbon and quietly emit a good deal through its upkeep. A rewilded garden builds a visible, growing store of carbon in wood and soil while making almost none of those emissions in the first place. The gap between them is real, but it opens up less through wild nature performing some magic trick, and more through a garden that gives instead of taking in many, many ways. So plant a tree. Let the hedge grow tall. Stop digging, stop spraying, put the mower away.

References & further reading

• Edmondson, J.L., Davies, Z.G., McHugh, N., Gaston, K.J. & Leake, J.R. (2012). Organic carbon hidden in urban ecosystems. Scientific Reports, 2, 963. (Leicester city-wide soil carbon; garden soils richer than assumed.)

• Edmondson, J.L. et al. (2014). Land-cover effects on soil organic carbon stocks in a European city. Science of the Total Environment, 472, 444–453. (Domestic gardens vs other greenspace; tree planting and garden soil carbon.)

• Townsend-Small, A. & Czimczik, C.I. (2010). Carbon sequestration and greenhouse gas emissions in urban turf. Geophysical Research Letters, 37, L02707. (Lawns as sink or source; mowing and fertiliser emissions; N₂O.)

• Gillman, S. et al. (2023) / follow-on syntheses on the greenhouse-gas balance of intensively managed lawns. (Intensive lawn footprint exceeding its sequestration potential over two decades.)

• Woodland Trust — carbon storage in trees and woodland. https://www.woodlandtrust.org.uk/climate-change/carbon-trees/

• Axe, J. et al. — carbon storage in hedge biomass (actively managed hedges in England), Agriculture, Ecosystems & Environment (2017). (Wider/taller hedges store more woody carbon.)

• Defra / Natural England — restriction on the retail sale of horticultural peat (2024); peatlands as the UK's largest carbon store.

• The Wildlife Trusts / RHS — climate-friendly gardening: trees, no-dig, peat-free, and reducing inputs. https://www.rhs.org.uk/ · https://www.wildlifetrusts.org/gardening