Nature-Based Solutions — Definition and GHG Accounting Context
The cheapest carbon-capture machine ever built is a forest, and the most reliable carbon store is a peatland left alone. For a decade, “using nature to fight climate change” has been the most popular — and the most contested — idea in corporate climate strategy, promising cheap tonnes at scale while attracting some of the sharpest greenwashing scrutiny in the market.
That whole family of interventions has a name. Nature-based solutions are actions to protect, restore and sustainably manage ecosystems that tackle societal challenges — climate change among them — while also delivering benefits for biodiversity and people.
Nature-based solutions (NbS) are actions to protect, restore and manage natural ecosystems that address societal challenges while benefiting biodiversity and people (UNEA, 2022). For climate, they cut emissions two ways: removals (restoring forests and soils to draw down CO₂) and avoided emissions (protecting ecosystems so stored carbon is not released). Their carbon credibility depends on additionality and permanence.
Definition — A Category of Action, Not a Technology
Nature-based solutions (NbS) are not a single technique but an umbrella for any action that works with ecosystems to solve a problem. The most widely used definition comes from the IUCN, which in 2016 defined NbS as “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”. In March 2022, UNEA resolution 5/5 adopted the first multilaterally agreed definition, broadening the scope to “terrestrial, freshwater, coastal and marine ecosystems” and to “social, economic and environmental challenges”.
Two features of that definition matter for greenhouse-gas work. First, NBS is defined by its means — an ecosystem doing the work — not by its end, so the same concept covers flood defence, water purification and heat reduction as well as carbon. Second, a genuine NBS must deliver biodiversity and human well-being benefits as well as its headline outcome; an intervention that stores carbon but harms an ecosystem (a monoculture plantation on drained peat, say) fails the definition. Climate mitigation is therefore only one of the challenges NBS address — but it is the one that turned NBS into a market.
The three verbs in the definition — protect, manage, restore — map directly onto how NBS show up in a carbon inventory. Protecting an intact ecosystem avoids an emission; restoring a degraded one produces a removal; improved management does some of each. That split is the single most important thing to get right when accounting for nature-based climate action, and the rest of this page turns on it.
Definition at a glance
| What it is | Actions that protect, restore or sustainably manage ecosystems to address societal challenges |
|---|---|
| Canonical definitions | IUCN (2016, Resolution 6.069); UNEA resolution 5/5 (2022, first multilateral definition) |
| Ecosystems covered | Terrestrial, freshwater, coastal and marine — forests, wetlands, grasslands, soils, mangroves, seagrass |
| Climate mechanisms | Two: removals (restore) and avoided emissions (protect) |
| Non-negotiable | Must also deliver biodiversity and human well-being benefits — not carbon alone |
| Where the risk sits | Additionality, permanence, leakage and monitoring — the market-integrity conditions |
NBS, Natural Climate Solutions, Nature-Based Credits
Three phrases circulate almost interchangeably, and the differences are worth pinning down because they narrow from broad to specific:
| Term | What it means | Scope |
|---|---|---|
| Nature-based solutions (NbS) | The full umbrella — ecosystem action for any societal challenge (climate, water, disaster risk, food, health) | Broadest |
| Natural climate solutions (NCS) | The climate-mitigation subset of NBS — the land-based pathways that store carbon or avoid emissions (Griscom et al., 2017 identified 20) | Climate only |
| Nature-based carbon credits | The financed slice — NCS interventions turned into tradable carbon credits on the voluntary carbon market | Narrowest |
So every nature-based credit is a natural climate solution, and every natural climate solution is a nature-based solution — but not the reverse. When a company says it is “investing in NBS”, it almost always means the narrow slice: buying nature-based credits. The Griscom study that produced the famous 37% figure quantified the middle category — natural climate solutions — estimating a maximum additional mitigation potential of 23.8 GtCO₂e per year by 2030 (of which roughly 11.3 GtCO₂e per year is cost-effective at a carbon price at or above US$100/tCO₂e). Forests supply the majority of that potential, with agriculture, grasslands and wetlands making up the rest.
The Two Climate Levers: Removals vs Avoided Emissions
This is the distinction that separates rigorous NBS accounting from marketing. Nature-based solutions mitigate climate change through two mechanisms that are counted completely differently and are not interchangeable:
| Lever | Verb | What happens | How it is counted |
|---|---|---|---|
| Removal | Restore | Reforestation, wetland restoration or building soil carbon actively pulls CO₂ out of the atmosphere | A removal — a negative emission, reported as its own line |
| Avoided emission | Protect | Preventing deforestation or peatland drainage stops carbon already stored from being released | An avoided emission — an emission that did not happen relative to a baseline |
The difference is not academic. A removal takes a tonne of CO₂ out of the air; an avoided emission simply keeps a tonne from going in. Only a removal actually reduces the atmospheric stock — which is why net-zero frameworks such as the SBTi FLAG target treat them separately, and why the difference between a removal credit and an avoidance credit is one of the most consequential lines in a company’s climate claims. Avoided-emission credits (most REDD+ forest-protection projects) also carry a harder integrity problem: proving what would have happened without the project — the counterfactual baseline — is far more contestable than measuring trees that are visibly growing.
The scale of the two levers, using live IPCC AR6 aggregates, shows why protection is often the bigger single prize: protecting one hectare of tropical forest avoids a one-time carbon pulse of about 165000 kg CO₂e (the land-use-change emission that clearing it would cause), whereas restoring a hectare removes only around 11,000 kg CO₂e per year. Avoidance can protect a large stock instantly; removal rebuilds it slowly.
How Much Nature Removes: Live Rates
When NBS act through the removal lever, the annual drawdown depends heavily on the ecosystem. Because these are removals, the live values carry a negative sign — a removal is a negative emission:
| Nature-based pathway | Net flux kg CO₂e / ha / year | Pool |
|---|---|---|
| Tropical forest restoration | -11000 | Biomass |
| Temperate broadleaf forest | -5800 | Biomass |
| Temperate conifer forest | -4900 | Biomass |
| Boreal forest | -2200 | Biomass |
| Improved grassland (soil) | -500 | Soil |
Forest restoration outpaces soil practices by an order of magnitude, and warm, fast-growing tropical forest leads by a wide margin. The pathways compared by magnitude:
Annual removal per hectare, kg CO₂e (IPCC AR6, live). Bar width is magnitude; the labels keep the negative sign because a removal is a negative emission. Every one of these rates slows over time as the forest matures or the soil carbon reservoir saturates — nature’s removal lever is not perpetual. The forestry & removals calculator estimates these by forest type and age.
NBS in Carbon Accounting and Markets
A hectare of growing forest is a physical fact; a creditable, sellable tonne of nature-based mitigation is a much harder thing to prove. The gap between the two is where NBS earn — or lose — their credibility. Four conditions decide whether a nature-based intervention counts in an inventory or a carbon market:
- Additionality — the carbon must be stored or protected because of the intervention or its finance, not something that would have happened anyway. This is the hardest test for forest-protection (avoided-emission) projects, whose baseline is a hypothetical.
- Permanence — the storage must last. Nature-based carbon is reversible: fire, drought, pests, harvest or reconversion can release it straight back. Standards manage this with buffer pools — a shared insurance reserve of un-issued credits.
- Leakage — protecting one forest must not simply push the deforestation next door. Genuine mitigation is net of any activity displaced elsewhere.
- Measurement, reporting & verification (MRV) — the tonnes must be quantified and independently tracked over time, not assumed from a rate table.
These conditions are why NBS is governed by a stack of standards rather than trusted on sight. Crediting programmes such as the Verra VCS issue and register nature-based units; the ICVCM Core Carbon Principles set a market-wide integrity threshold that a credit type must clear to be labelled high-integrity; and for corporate inventories the GHG Protocol Land Sector and Removals Guidance governs how a company reports nature removals — separately from gross emissions, never netted against them.
Under the mitigation hierarchy, nature-based solutions are a complement to deep decarbonisation, not a substitute for it: cut your own emissions first, then use high-integrity NBS to address the residual. To size and price that residual, the carbon offset cost calculator and the carbon removal (CDR) calculator compare nature-based options against engineered ones.
More Than Carbon: The Biodiversity Test
It is easy to reduce NBS to “buying tree credits”, but the definition explicitly refuses that reduction. The IUCN Global Standard for NbS (2020) sets out eight criteria — supported by 28 indicators — that an intervention must meet to qualify, spanning effective response to a societal challenge, appropriate scale, net biodiversity gain, economic viability, inclusive governance, balanced trade-offs, adaptive management and mainstream sustainability. A project that maximises carbon while degrading an ecosystem — draining a peatland to plant fast-growing trees, or replacing species-rich habitat with a monoculture — is not a nature-based solution at all, however many credits it issues.
For greenhouse-gas practitioners, the practical upshot is that the carbon claim and the nature claim travel together. Buyers increasingly scrutinise the co-benefits — biodiversity, water, community livelihoods — as closely as the tonnes, and standards are building those requirements into their methodologies. A nature-based tonne that comes at nature’s expense is a contradiction in terms.
Common Confusions
- Treating removals and avoided emissions as the same thing. Restoring a forest is a removal (a tonne taken out of the air); protecting one is an avoided emission (a tonne kept from going in). They are counted differently and are not interchangeable in a net-zero claim.
- Equating NBS with offsetting. NBS is a category of ecosystem action; offsetting is one way to finance a slice of it. Much NBS finance (protected-area funding, restoration grants, insetting inside a value chain) never becomes a tradable credit at all.
- Assuming nature-based carbon is permanent. It is reversible — fire, drought, harvest or reconversion can release it. Permanence is a condition to be managed (via buffer pools), not a property to be assumed.
- Confusing NBS with engineered removals. Direct air capture and BECCS are technological removals, not nature-based ones. NBS works through living ecosystems; engineered carbon dioxide removal does not.
- Reducing NBS to carbon. By definition an NBS must also deliver biodiversity and human well-being benefits. A carbon project that harms an ecosystem fails the definition, regardless of the tonnes it claims.
Frequently Asked Questions
Nature-based solutions (NbS) are actions to protect, sustainably manage and restore natural or modified ecosystems that address societal challenges — including climate change — while simultaneously delivering benefits for biodiversity and human well-being. The definition comes from the IUCN (2016) and was adopted multilaterally by the UN Environment Assembly in resolution 5/5 (2022). For climate, NBS reduce emissions through two mechanisms: removals, where restoring forests, wetlands and soils draws CO₂ out of the atmosphere, and avoided emissions, where protecting an intact ecosystem prevents stored carbon from being released. NBS is an umbrella category, not a single technology.
Natural climate solutions (NCS) are the climate-mitigation subset of nature-based solutions. NBS is the broad umbrella covering ecosystem action for any societal challenge — flood defence, water quality, food security and heat reduction as well as carbon. NCS narrows that to the land-based pathways that specifically store carbon or avoid greenhouse-gas emissions; Griscom et al. (2017) identified 20 such pathways across forests, wetlands, grasslands and agricultural lands, estimating they could deliver up to 37% of the cost-effective CO₂ mitigation needed by 2030. Narrower still are nature-based carbon credits — the slice of NCS that is financed through the voluntary carbon market. Every credit is an NCS, and every NCS is an NBS, but not the reverse.
No. Nature-based solutions are a category of ecosystem action; offsetting is one way of financing a slice of them. Some NBS become tradable carbon credits — a reforestation project or a REDD+ forest-protection project sold on the voluntary market — but much NBS finance never does: protected-area funding, public restoration programmes, and insetting inside a company’s own value chain are all NBS without being offsets. Under the mitigation hierarchy, using NBS credits to offset should come only after cutting your own emissions, and address the residual rather than substitute for reduction.
Because two of their integrity conditions are genuinely hard to prove. Additionality requires showing the carbon was stored or protected because of the project — and for forest-protection (avoided-emission) credits that means proving a counterfactual, how much deforestation would have happened without it, which several REDD+ programmes have been shown to overstate. Permanence is the second problem: nature-based carbon is reversible by fire, drought or harvest, so a credit sold today can be undone tomorrow. Add the risk of leakage — displacing deforestation elsewhere — and it is clear why the ICVCM Core Carbon Principles and standards such as Verra now apply tighter baselines, buffer pools and monitoring.
At the global scale, Griscom et al. (2017) estimate natural climate solutions have a maximum additional mitigation potential of about 23.8 GtCO₂e per year by 2030, of which roughly 11.3 GtCO₂e per year is cost-effective at a carbon price of US$100/tCO₂e or above. At the project scale, removal rates vary widely by ecosystem: using the live IPCC AR6 aggregates, a growing tropical forest removes around -11000 kg CO₂e per hectare per year, temperate forest -5800 to -4900 kg, boreal forest about -2200 kg, and soil practices such as improved grassland only about -500 kg. The values are negative because a removal is a negative emission, and all of these rates slow as the ecosystem matures and its carbon reservoir saturates.