Nature-based
solutions forclimate change
mitigation© 2021 United Nations Environment Programme
ISBN: 978-92-807-3897-1
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Published by: United Nations Environment
Programme (UNEP), Nairobi and International Union
for Conservation of Nature (IUCN), Gland
Citation: United Nations Environment Programme
and International Union for Conservation of Nature(2021). Nature-based solutions for climate change
mitigation. Nairobi and Gland.
Authors: Lera Miles1, Raquel Agra1, Sandeep
Sengupta2, Adriana Vidal2, Barney Dickson3
Contributors: Juliet Mills1, Julieta Lahud1,
Carina Pohnke1
Acknowledgements: UNEP and IUCN thank thefollowing reviewers: Patrick Lutz (Federal Ministry
for the Environment, Nature Conservation and
Nuclear Safety (BMU), Germany); Alex White(Department for Environment, Food and Rural
Affairs (Defra), UK); Karin Zaunberger (European
Commission); Nathalie Seddon (University of
Oxford); Mario Boccucci (UN-REDD Programme): Tim
Christophersen, Andrea Hinwood, Gabriel Labbate,
Susan Mutebi-Richards (UNEP); Stewart Maginnis,
Chris Buss (IUCN); Neil Burgess, Rodrigo Cassola,
Katie Dawkins, Cordula Epple, Charlotte Hicks,
Judith Walcott (UNEP-WCMC).
This report was made possible through thegenerous contribution of our donors: Ministry
for Ecological Transition, Italy, Federal Ministry
for the Environment and Agence française dedéveloppement (AFD), France.

1 UNEP World Conservation Monitoring Centre, Cambridge
2 IUCN, Gland
3 UNEP, Nairobi

UN Environment Programme promotes
environmentally sound practices
globally and in its own activities. Our
distribution policy aims to reduce
UNEP’S carbon footprint. The report is
printed on recycled paper.

Table of Contents

Key Messages

1

1 Introduction

42 What are nature-based solutions?

5

3 How much can nature-			
based solutions contribute to 		
mitigation?

7

3.1 The climate change
mitigation challenge
3.2 Studies of the mitigation 		
potential of nature-based 			solutions
3.3 How can different naturebased solutions contribute to 		climate change mitigation?
3.4 Further nature-based 			solutions could be possible in 		
marine ecosystems
3.5 How much mitigation can 		
we expect from nature-based 		
solutions?

7
8
12
15
16

4 Nature-based solutions offer 		multiple benefits

17

5 Social and environmental 		safeguards

20

6 Increasing support for nature-		
based solutions

22

6.1 Nature-based solutions in
national mitigation 			
commitments
6.2 Private sector 			commitments on climatechange mitigation
6.3 Partnerships for naturebased solutions

22
24
25

7 Financing needs

26

8 How can offsets play a role?

27

9 Conclusion

32

References

33

Key Messages

1
2

A cautious interpretation of the existing evidence, taking account of associateduncertainties and the time needed to deploy safeguards, indicates that by 2030, naturebased solutions implemented across all ecosystems can deliver emission reductions andremovals of at least 5 GtCO2e per year, of a maximum estimate of 11.7 GtCO2e per year.
By 2050, this rises to at least 10 GtCO2e per year, of a maximum estimate of 18 GtCO2e
per year. This is a significant proportion of the total mitigation needed.

3

Approximately 62 per cent of this contribution is estimated to come from nature-based
solutions related to forests, about 24 per cent from solutions in grasslands and croplands,
and 10 per cent from additional solutions in peatlands. The remaining 4 per cent will comefrom solutions implemented in coastal and marine ecosystems. The balance of actions to‘Protect, Manage and Restore’ different ecosystems will vary.

4

1

The Intergovernmental Panel on Climate Change (IPCC) scenarios for emission reductions
are clear. In order to keep temperature rise close to the Paris Agreement goal of 1.5°C wemust achieve net zero CO2 emissions by 2050. The scenarios show that this will require,in addition to a massive and rapid decarbonization, a significant contribution from landbased options. Nature-based solutions provide the best way of delivering these land-based
options, through protection, restoration and sustainable management of natural carbon
sinks and reservoirs. Moreover, there is additional mitigation potential from nature-based
solutions in coastal and marine ecosystems.

This contribution by nature-based solutions will require adherence to strict socialand environmental safeguards to avoid harm. Much careful work has already been
undertaken on the formulation of such safeguards. This is reflected in tools such as theInternational Union for Conservation of Nature (IUCN) Global Standard for Nature-based
Solutions, and in more ecosystem-specific instruments such as the Cancun safeguards
for REDD+ (Reducing Emissions from Deforestation and forest Degradation, plus thesustainable management of forests, and the conservation and enhancement of forest
carbon stocks). The implementation of these safeguards should be undertaken withequal care and determination.

5Countries frequently reference nature-based solutions for mitigation in their Nationally
Determined Contributions (NDCs) to combating climate change and its effects. The 100
NDCs reviewed for this report showed a greater focus on actions in forest than in otherecosystems, and there were slightly more commitments to Manage and Restore than toProtect carbon stocks in ecosystems.

6

Nature-based solutions, when done well, can deliver many different benefits, including
for climate change adaptation and biodiversity conservation. They should therefore beplanned, designed and implemented so as to deliver those benefits.

7

The contribution from nature-based solutions needs additional finance. This will require
action by and close coordination between public and private actors. It is essential that
where the private sector purchases nature-based solutions offsets as part of its pathways
to achieve net zero, these offsets are in accordance with social and environmental
safeguards and, moreover, are a small part of a wider mitigation strategy focused
primarily on deep decarbonization. The development of rules and guidance in this area
is now underway.

8

The value and importance of nature needs to be better reflected in economic and politicaldecision-making and in a stronger integration between the biodiversity, climate change anddevelopment agendas. Failure to achieve this will exacerbate climate change and otherimportant societal challenges, and the Sustainable Development Goals will not be achieved.

2

3

1

Introduction

The need to mitigate climate change, and the rolethat nature can play in doing so, are recognized undermultilateral agreements, including the United Nations
Framework Convention on Climate Change (UNFCCC)
and the Convention on Biological Diversity (CBD).
However, we are collectively on a path towards failingto meet the UNFCCC’s Paris Agreement commitment
to limit warming to well below 2°C, preferably 1.5°C,
as well as CBD targets on biodiversity. So far, humanactivities have been responsible for a global mean
temperature rise of nearly 1.1°C relative to 1850–
1900 levels. If we continue on the current course, it isincreasingly likely that the 1.5°C limit will be exceededin the next 20 years (Intergovernmental Panel on
Climate Change [IPCC] 2021).
Immediate, far-reaching action to rapidly cut
greenhouse gas emissions and remove CO2 from theatmosphere is necessary if the worst consequencesof climate change are to be avoided. Transformativechanges of a type never before attempted are
required (Pörtner et al. 2021). The 2020 Emissions
Gap Report showed that countries need tocollectively increase their mitigation ambitions“threefold to get on track to a 2°C goal and morethan fivefold to get on track to the 1.5°C goal” (United
Nations Environment Programme [UNEP] 2020,p.21). A key action needed to achieve these goals
is decarbonizing our economy – radically reducing
and eliminating emissions from fossil fuels in energy
generation, industry and transport.

While nature-based solutions are a necessary
complement to decarbonization, they can only be
relied upon when combined with rapid, wide-ranging
emissions reductions from energy, industry andtransport. Without this dual approach, the total
mitigation achieved will be insufficient to avoid
climate-related risks (such as changes in temperatureand rainfall) that reduce the ability of nature-based
solutions to contribute to climate change mitigation(Pörtner et al. 2021).
Despite growing political support for the useof nature-based solutions in climate change
mitigation, a number of concerns have been raised.
These include: uncertainties about the scale ofthe contribution, especially given challenges with
implementation and financing; doubts about whether
the necessary safeguards will be put in place; andworries about the use of offsets by the private sector.
This report will assess the current state ofknowledge on the size of the contribution that naturebased solutions can make and the types of action
they will involve. It will discuss the importance ofsocial and environmental safeguards, how naturebased solutions can be financed and the role ofoffsets. Most importantly, it will consider the
potential of nature-based solutions for mitigation
to also contribute to climate adaptation and otherpressing challenges.

All IPCC mitigation pathways consistent with limiting
temperature rise to 1.5°C involve, in addition to
decarbonization, very significant changes in current
land-use trajectories to tackle and reverse theseemissions. Although the IPCC does not call them‘nature-based solutions’, these pathways do include
actions of this type, including a halt to deforestation.
Achieving the Paris Agreement target of 1.5°C
will therefore require a significant contribution
from nature-based solutions, as well as the rapid
decarbonization of our economies.

4

2

What are nature-based solutions?

This report uses the definition of nature-based
solutions adopted by the International Union forConservation of Nature (IUCN) at its 2016 World
Conservation Congress. According to thisdefinition, nature-based solutions are “actions toprotect, sustainably manage, and restore natural
or modified ecosystems, that address societal
challenges effectively and adaptively, simultaneously
providing human well-being and biodiversity
benefits”1 (IUCN 2016). The definition does notinclude ‘nature-derived’ solutions, such as the useof wind, wave and solar energy, or ‘nature-inspired’
solutions, such as design of materials modelled on
biological processes (IUCN 2020a). Further, the IUCN
Global Standard for Nature-based Solutions includes
eight specific criteria2 and 28 indicators, intended toenable the coherent design, execution and evaluationof nature-based solutions (IUCN 2020b), while
complementary guidelines3 (Seddon et al. 2021)
have been adopted by the ‘Together With Nature’
campaign4. Well-designed and -implemented naturebased solutions deliver multiple benefits, enablingsynergies and minimizing trade-offs in achieving
different global development objectives as set out in
the Sustainable Development Goals. Nature-based
solutions can simultaneously address societal
challenges, including climate change mitigation andadaptation, natural disasters, human health, food andwater security, and biodiversity loss. This potential
has encouraged widespread adoption of the concept,
including in resolutions by the G7, the G20, the United
Nations General Assembly, and in international
dialogues and private sector guidance (World
Business Council for Sustainable Development[WBCSD] 2020; UNEP 2021a).
While some nature-based solutions are primarily
intended to contribute to climate mitigation, others
may provide mitigation as an additional benefit totheir main goal. Given the ability of nature-based

solutions to contribute to more than one goal, inpractice the distinction between these different typesof solutions is not always clear. Nevertheless, in thecontext of climate action, the specific concept ofnature-based solutions for mitigation is useful, as it
highlights the differences between this solution andother approaches to mitigation. In line with the overall
IUCN definition, nature-based solutions for mitigation
include actions to protect natural ecosystems fromloss and degradation, restore ecosystems thathave been degraded, and more sustainably manage
working lands such as fields and managed forests.
These three categories encompass many specifictypes of action – or ‘response options’, as they arecommonly known – ranging from Avoided Forest
Conversion to Improved Rice Cultivation. Together,
they can reduce greenhouse gas emissions arisingfrom the loss, degradation and mismanagement of
ecosystems, and increase natural CO² sequestration.
A related concept is that of ‘natural climate solutions’(Griscom et al. 2017), described as a subset of
nature-based solutions focused on climate change
mitigation (Girardin et al. 2021), though there is one
difference in the way that these two concepts areoften understood. The IUCN Global Standard expects
all nature-based solutions to have a net positive
impact on biodiversity, and to include and empower
all affected stakeholders with mutual respect andequality, regardless of gender, age or social status. In
contrast, the World Business Council for Sustainable
Development (WBCSD) suggests that, as a minimum,
natural climate solutions need only result in zeronet loss for biodiversity, although it does encourage“high-quality” natural climate solutions that are “netpositive for nature and biodiversity, and also support
people and local communities” (WBCSD 2020, p.4).
A consequence of the IUCN definition of nature-based
solutions used here is that a number of land uses,

1This definition is closely aligned with European Commission (EC) and Organisation for Economic Co-operation and Development (OECD)
definitions, which also reference economic dimensions (OECD 2020; EC 2021), with the EC adding a focus on building resilience.
2 Criteria: (1) effectively address societal challenges; (2) design is informed by scale; (3) result in a net gain to biodiversity and ecosystem
integrity; (4) economically viable; (5) based on inclusive, transparent and empowering governance processes; (6) equitably balance trade-offs
between achievement of their primary goal(s) and the continued provision of multiple benefits; (7) managed adaptively, based on evidence; (8)sustainable and mainstreamed within an appropriate jurisdictional context.
3 The Nature-based Solutions to Climate Change guidelines were originally developed in February 2020 as a letter to the President of CoP26,
Alok Sharma, to encourage other Parties to the UN Framework Convention on Climate Change (UNFCCC) to adopt these solutions. Available at:https://nbsguidelines.info/ and in Seddon et al. (2021).
4 The ‘Together With Nature’ campaign, a call to corporate leaders to commit to four principles for investing in nature-based solutions, adopted
the Nature-based Solutions to Climate Change guidelines in May 2020. See: https://www.togetherwithnature.com/

5including some that feature in the aforementioned
IPCC mitigation pathways, do not qualify as naturebased solutions. One such land use involves the
carbon dioxide removal (CDR) technology ‘bioenergy
with carbon capture and storage’ (BECCS), which,to date, exists only in pilot projects. This technology
uses bioenergy instead of fossil fuels for power
generation, and stores the emissions in undergroundgeological formations. BECCS features in the IPCC
pathways at a very large scale, and it is therefore
essential that land-demanding measures of thistype deliver positive overall outcomes, including forfood security, poverty alleviation and biodiversity
conservation. However planting bioenergy crops(trees, perennial grasses or annual crops) for BECCS
over a large share of land is harmful to natural
ecosystems and their services, and competes withfood production for both land and water (Harper et al.
2018; Fajardy et al. 2019; Pörtner et al. 2021; Stenzel
et al. 2021).
Nature-based solutions that absorb carbon fromthe atmosphere are sometimes consideredalongside more industrial carbon dioxide removal
options including BECCS, direct air capture andstorage of CO², and enhanced weathering of
crushed silicate rocks (Field and Mach 2017). For
any of these latter options to make a significant
contribution to mitigation they would need to bescaled up dramatically from current trials. Not
only do we have much more practical experience
with nature-based solutions, but their capacity todeliver multiple benefits far outweighs that of theseindustrial options.

6

3

How much can nature-based solutions
contribute to mitigation?

3.1 The climate change mitigation challenge
Halting climate change will require radical andtransformative change. There is an urgent need to:(1) enhance the NDCs that countries have committed
to, but which collectively fall far short of meeting
the Paris Agreement goals (Fekete et al. 2021); (2)deliver on these NDC commitments; (3) develop
and implement ambitious Long-Term Low Emission
Development Strategies, (4) promote behaviouralchange and new social norms5; and (5) invest in
low-carbon post-COVID-19 recovery measures acrosssectors (UNEP 2020; UNEP 2021b).

from fossil fuels and the remainder included
methane (CH4), nitrous oxide (N2O) and fluorinatedgases as well as CO2 from land-use change (UNEP2020) (Figure 1). Agriculture, forestry and other landuse (AFOLU) activities were responsible for around23 per cent of the net anthropogenic greenhousegas emissions between 2007 and 2016 (12.0 ±2.9
GtCO2eq yr-1) (IPCC 2019)6. This proportion is
gradually decreasing as a result of an overall increasein emissions, rather than a decrease in emissions
from AFOLU including land-use change (Figure 1).

For an 83 per cent chance of limiting warming to
1.5°C, the IPCC estimates that, from 2020, total
emissions must be no more than 300 GtCO2 (the‘global carbon budget’) (IPCC 2021). The same
calculations for 2°C yield a 900 GtCO2 budget.
However, the added half-degree of warming brings
with it much greater risk, including from wildfire,
permafrost degradation and food insecurity (IPCC
2019; IPCC 2021). To stay within the 1.5°C limit,
we need to reach global net zero targets for CO2
emissions by 2050 and strongly reduce emissions ofother greenhouse gases (IPCC 2018).

The Earth’s marine and terrestrial ecosystems
take up around 56 per cent of anthropogenic CO2(IPCC 2021). In recent decades, while the annual
global sink has increased, there has been a trend ofincreasing absorption in the northern hemisphereand a decrease in the southern hemisphere (Ciais
et al. 2019), the causes of which include land coverchanges (including patterns of loss and recoveryof natural ecosystems) and a slow saturation of
the Amazon forest carbon sink (Hubau et al. 2020).
Nature-based solutions involve human interactions
with the natural world, to protect, restore or better
manage this natural capacity to absorb and store
atmospheric carbon. These include AFOLU activities
and the management of marine, coastal andfreshwater ecosystems.

Global greenhouse gas emissions (GtCO2e)

Between 1990 and 2019, greenhouse gas emissions
from all sources increased. In 2019, 59.1 (±5.9)
GtCO2e were emitted, of which 65 per cent was CO2,60

Land-use change (CH4+N2O)
Land-use change (CO2)50

Fluorinated gases (F-gas)

40

N2O

30

Fossil CO2

CH4

20
10
0

1990

1995

2000

2005

2010

2015

2019

Figure 1: Global greenhouse gas emissions from all sources between 1990 and 2019
(Reproduced from UNEP 2020)
5 “Equity is central to addressing lifestyles. The emissions of the richest 1 per cent of the global population account for more than twice the
combined share of the poorest 50 per cent.” (United Nations Environment Programme 2020)
6 In addition, food systems generate emissions that are not part of the AFOLU estimates, for example through food processing, transport,
fertiliser synthesis.

73.2 Studies of the mitigation potential of nature-based solutions
Several recent syntheses have provided estimatesof the mitigation potential of nature-based solutions;
here we provide an overview and comparison(Table 1). At the global scale, it is possible to jointly
estimate the mitigation potential of many individual
nature-based solutions, or response options (IPCC
2019). The studies compared in this report aimed
to avoid any double-counting of this potential that
could result from overlaps in land requirements
between the options they included. Estimating thepotential and avoiding overlaps often involved spatial
analysis of areas suitable for different options. To
enable comparison across studies, here we adopt
the typology of options from Griscom et al. (2017).
In modelling the land area available for each option,these analyses often approximate some of the IUCN
Global Standard’s criteria, for example by ruling out
conversion of natural ecosystems. But it is only whenplanning, implementing and monitoring a naturebased solution in a particular geographical context
that it is possible to ensure that these criteria or otherrelevant safeguards are met in practice.
Most of the nature-based solutions included, andmost of the mitigation estimated, are terrestrial. All
syntheses included conservation and restoration ofsome coastal ecosystems, but there is substantiallymore terrestrial than marine research on the potential
scale of nature-based solutions, their benefits
and risks, and related uncertainties. Some studies
included land management response options thatare not nature-based solutions and are unproven,such as BECCS. The studies also varied in the rangeof response options they considered. In the analysis
below, we have extracted the information on the
mitigation potential of nature-based solutions alone,while noting where the studies have also included
options such as BECCS in calculating their results.
The effectiveness of nature-based solutions forclimate change mitigation is dependent on theresilience of the ecosystems to the impacts ofclimate change itself. Their ability to act as a sink
for CO2 emissions is directly and indirectly affectedby their climate change exposure, sensitivity andadaptive capacity (Seddon et al. 2020). Climatechange can increase the exposure of ecosystems
to pressures such as fire, drought, biotic agents,and other disturbances, and also to indirect impacts
from human migration. These permanence risks
are projected to increase in the twenty-first century(Anderegg et al. 2020). By enhancing the resilienceof carbon stocks to the impacts of climate change,well-designed nature-based solutions can also reduceclimate change feedbacks that release further CO2(Pörtner et al. 2021). But this resilience can only
go so far: nature-based solutions will only function
reliably in a world that takes decisive action to
decarbonize the economy. Neither climate impacts
nor the effects of management on resilience are
directly addressed in the analyses of the potential ofnature-based solutions reviewed here.
In a foundational study, Griscom et al. (2017) brought
together estimates for the mitigation potentialof 20 nature-based solutions response options(‘pathways’). All the later syntheses reviewed here
draw on at least some elements of this first study(hereafter, ‘Griscom’). First, Griscom calculated amaximum potential across all options and compatible
with certain biodiversity and food security safeguards(23 GtCO2e per year). When parameters were further
restricted to solutions that cost up to US$ 100/tCO2,
11.3 GtCO2e per year was found to be possible, or 4.1
GtCO2e per year if only budgeting for US$ 10/tCO2.
In a widely cited conclusion, this study estimatedthat these solutions could contribute 37 per cent of
the greenhouse gas mitigation needed at 20307 for a>66 per cent chance of remaining below a 2°C global
mean temperature increase, at a cost of no more than
US$ 100/tCO2. The projected carbon benefits fromnature-based solutions increased linearly from 2016
to 2025, were maintained until 2060, and were thenassumed to decline as the capacity of ecosystems toabsorb CO2 saturated. Given the 2016 start year, thisdegree of scaling up by 2030 now looks optimistic.
Roe et al. (2019) built on this analysis to identify
potential land sector contributions to a mitigation
objective of limiting global mean temperature rise
to no more than 1.5°C. This study (hereafter ‘Roe’)integrated some additional agricultural studies,
as well as demand-side response options such as
dietary shift and reduction in food waste, and a
BECCS response option. In our focus on nature-based
solutions, we exclude BECCS and the demand-side
options from our summary. Roe selected a set of
response options, taking into account feasibility,
risks and multiple benefits, to contribute ‘wedges’of emissions reductions at 2050. The total 2050
mitigation potential for nature-based solutions was
slightly higher than in Griscom, at 12.1 GtCO2e per
year. The biggest difference for 2050 was in thescope of the Protect actions included, which in
Griscom were constrained to a cost of US$ 100/tCO2,
and in Roe were not. However, in Roe the solutions,especially for Manage and Restore, are scaled
up more slowly than in Griscom. As a result, Roe

7 The overall emissions reduction trajectory used here follows Meinshausen et al. (2009)8

estimates a much smaller 2030 mitigation potential
than any of the other studies (at least 5 GtCO2e per
year, see Table 1).
Also in 2019, an IPCC special report on climatechange and land included a detailed review ofdifferent land sector response options, including
their benefits for climate change mitigation,
adaptation and avoiding desertification and landdegradation (IPCC 2019). The report reviews
technical potential for the different options, andthe scale of the multiple benefits they may deliver.
However, it does not include an overall estimate ofland-based mitigation potential.
Girardin et al. (2021) focused on evaluating
the impact of nature-based solutions on global
temperature rather than emissions, using scenariosthat limit temperature rise to no more than 1.5°C
and 2°C. In addition, this study (hereafter ‘Girardin’)updated the Griscom mitigation potential estimatesat US$ 100/tCO2. However, it did not integrate four
Griscom response options that feature non-CO2
emissions reductions. Hence, the study reported
a 2030 mitigation potential of 10.1 GtCO2 per year
(Table 1), while the same updates made to theoriginal synthesis would have yielded a potential
11.1 GtCO2e per year. Notably, Girardin allocates amuch greater potential to agroforestry (1.86 versus
0.44 GtCO2 per year) and a smaller potential toreforestation (1.48 versus 3.04 GtCO2 per year) and tocoastal wetland restoration (0.08 versus 0.20 GtCO2
per year) than Griscom (Figure 2). The study updated
both tropical and temperate reforestation estimates.
No boreal reforestation and no afforestation ofnatural ecosystems or of croplands was included ineither Griscom or Girardin.
The <1.5°C scenario developed in Girardin assumed
a far greater implementation both of nature-based
solutions and of BECCS than the <2°C scenario. In
the 1.5°C scenario, nature-based solutions wereallowed to reach 10 GtCO2 per year by 2025, and 20
GtCO2 per year by 2055. By interpolation, this yields
an estimate of 11.7 GtCO2 per year by 2030, and18.3 GtCO2 per year by 2050 (Table 1). A higher value(US$/tCO2e ) was assigned to emissions reductions
and removals in this scenario. From 2055, the CO2
removal technology known as ‘direct air capture’ wasassumed to mature and deliver more of the required
mitigation. There may be conflict between the land
expected for BECCS under this scenario and that for
nature-based solutions implementation.
As this report was being finalized, a new paper was
released that brings together sectoral estimates

9of mitigation potential and integrated assessment
model estimates, both allocated across 200 countries
and smaller territories (Roe et al. 2021). As well as
options that could be seen as nature-based solutions,these include dietary shifts, food waste reduction
and, in the integrated assessment models, a small
contribution from BECCS. The new study finds apotential of 8 to 13.8 GtCO2e per year between 2020
and 2050, at a cost of up to US$ 100/tCO2e, acrossall these response options. While it has not beenpossible to analyse these results in detail in thecurrent report, the range is broadly consistent withearlier studies of nature-based solutions potential.
In addition to the traditional peer reviewed literature,
two further syntheses have been developed, with
contrasting results. Both draw on Griscom forsome response options. First, for the non-profit
Project Drawdown, a large set of response options
were considered, encompassing climate change
mitigation across sectors (Wilkinson 2020). Theseare quantified to develop two emissions scenarios,roughly consistent with limiting global mean
temperature rise to no more than 1.5°C or 2°C. The
analysis is an outlier with, notably, a much greater
cumulative nature-based solutions mitigation
potential by 2050 in the <1.5°C scenario comparedto the other syntheses. While direct comparisonof potential GtCO2e per year at 2030 and 2050 isdifficult, it is noticeable that this study consideredmore agricultural land management options andidentified a much greater proportion of potentialfrom Manage actions and a smaller proportion fromProtect actions than the other studies did.
Second, in an analysis for the World Economic Forum(WEF), only eight response options are contemplated,roughly matching up with nine of the Griscom
options (McKinsey & Company 2021). Partly as aconsequence of this smaller number, this analysis
has a lower estimate of mitigation potential by 2030,
at 6.7 GtCO2/year. It also takes a different approachto estimating ‘practical’ mitigation potential, usuallyfocused on ‘land rent’: the agricultural return value
per hectare. Practical areas for implementation
were those with land rents up to US$ 45 per hectare.
The analysis investigates only two of the Manage
options from Griscom: agroforestry and conservation
agriculture. Unsurprisingly, it finds much lesspotential in ecosystem management actions thanthe other synthesis studies. Its overall estimatesfor Protect and Restore options are close to thoseof Girardin.

Griscom et al. 2017

Roe et al. 2019

Girardin et al. 2021

McKinsey &Company 2021

Wilkinson 2020

Cost constraints

Mitigation objective(max °C)

Source2030 mitigation
potential GtCO2e/year*

Protect Manage Restore

2<US$
100/tCO2e

1.5

Mixed (max;<US$ 25/tCO2e;<US$
100/tCO2e)

-

-

-

1.5

<US$ 100/tCO2e
until 2025; <US$
200/tCO2e2025-2055

2<US$ 100/tCO2e

3.9

4.3

-

Mixed (mainly
land rents<US$ 45/ha)

3.8

1.5

Mixed

2

Mixed

3.6

2050 mitigation
potential GtCO2e/year*

2020-2050 mitigation
potential GtCO2e*

All

Protect Manage Restore

All

Protect Manage Restore

All

3.9

3.8

11.3

3.9

3.8

3.6

11.3

-

-

-

288.2

3.4

>0.7† >0.9† >5.0

4.6

3.9

3.6

12.1

-

-

-

11.7
(10 at
2025)

-

-

-

18.3
(20 at
2055)

-

-

-

380.0

2.0

10.1

3.9

4.3

2.0

10.1

-

-

-

280.0

0.8

2.1

6.7

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

>18.5‡ 54.3

334.7 164.7 553.7

-

-

-

-

-

-

-

>11‡ 33.5

188.0 108

329.5

Table 1: Nature-based solutions syntheses(Sources: Griscom et al. 2017; Girardin et al. 2021; McKinsey & Company 2021; Roe et al. 2019; Wilkinson 2020)
Figures in italics are derived from results reported in the study concerned.
*Girardin et al. 2021 and McKinsey & Company 2021 include CO2 options only; Griscom et al. 2017,
Roe et al. 2019, and Wilkinson 2020 include additional greenhouse gases, hence CO2e†i.e. > 2020–2030 total divided by 10‡i.e. > 2020–2050 total divided by 30

10We have seen that one reason for the wide range of
mitigation potential identified in these studies (Table
1) is the different assumptions made about the
global willingness to fund climate change mitigationin general and nature-based solutions in particular.
Whether covered by public or private means, thiscan be represented by a US$ value (cost or price)
per tonne of emissions reductions and removals. A
cost of no more than US$ 100/tCO2e has frequently
been used as a basis for estimating ‘feasible’
mitigation potential, within biophysical, social andenvironmental constraints. In half of all tropicalcountries, over 50 per cent of national emissions
could be mitigated through nature-based solutions
at a cost of less than US$ 100/tCO2e (Griscom et al.
2020). However, Girardin envisaged that achieving
a 1.5°C scenario would require doubling theacceptable cost of mitigation to US$ 200/tCO2e. Thisapproximately doubled the global mitigation fromnature-based solutions available by 2050.

11

US$ 200/tCO2e is very high in comparison toavailable payments for nature-based solutions in thepresent day, such as the US$ 10/tCO2e minimum
price available for forest emissions reductions via theLowering Emissions by Accelerating Forest finance(LEAF) Coalition (LEAF Coalition 2021). While anincreased willingness to pay for mitigation could
incentivize greater use of nature-based solutions,
it would also incentivize a suite of other climatechange mitigation actions. The financing of naturebased solutions may depend, in part, on their costeffectiveness compared with these other options.
Although nature-based solutions can deliver a rangeof benefits in addition to climate change mitigation,
many of these are not captured by traditional
cost-benefit analysis, even though they can make atangible difference to peoples’ lives.

3.3

How can different nature-based solutions
contribute to climate change mitigation?
The response options included in the studies
reviewed here can be compared through different
lenses: (i) options to Protect, Manage and Restore
ecosystems; and (ii) the way that these are divided
among different ecosystems. These comparisons
will help to clarify the potential carbon benefits from,and the scope for strengthening effort towards,
different types of nature-based solutions.
Here we summarize some of the nature-based
solutions with the greatest mitigation potential,
highlight some enabling conditions for eachmajor group of solutions and suggest someresearch priorities.
Solutions that Protect Ecosystems
In general, reducing emissions by preventing theloss or degradation of natural ecosystems is morecost-effective and immediate than restoring carbon
to damaged ecosystems. This is consistent witha mitigation hierarchy approach to impacts on
biodiversity and ecosystem services, which indicatesthat impacts should first be avoided; when that is notpossible, they should be minimized; and when they dooccur, restoration should take place (Ekstrom, Bennun
and Mitchell 2015; Tallis et al. 2015). If impacts
remain, they should be offset by equivalent action
elsewhere. All else being equal, it follows that the firstpriority is to Protect ecosystems from conversion,
the second step is to tackle the drivers of ecosystemdegradation, and the third is to Restore ecosystems.
Tropical forests, peatlands, and mangroves havethe highest carbon stocks per hectare of all natural
terrestrial/coastal ecosystems (Epple et al. 2016).
In the latter two ecosystems, much of the carbon
is held in soil organic carbon: 1375 tonnes/hectare
on average for peatlands worldwide (Joosten andCouwenberg 2008) and 361 tonnes/hectare for
mangroves (Sanderman et al. 2018). When peatlands
and coastal wetlands are drained or otherwise
degraded, they lose their soil organic carbon stores
to the atmosphere through oxidation and sometimes
burning. However, given the different areas of theecosystems under pressure (Epple et al. 2016), theresponse option of Avoided Forest Conversion has apotential four to five times that of Avoided Peatland
Impacts, and 10 to 12 times that of Avoided Coastal
Wetland impact, including mangroves, saltmarshes
and seagrass beds (Griscom et al. 2017; Roe etal. 2019; Girardin et al. 2021). Most estimates foravoided forest conversion are focused on a rangeof actions to reduce tropical deforestation, although
Project Drawdown considers all forests but only in thecontext of declaring protected areas and establishingindigenous peoples’ tenure.

Nature-based solutions that require ecosystem loss
to be avoided are only possible on a global scale ifaction is taken to tackle demand for agricultural land,
the largest driver of land use change (the same willoften be true for Restore actions). On the supply side,
this can involve sustainable intensification, whichseeks to improve crop yields without increasing
carbon emissions. Unsustainable production andconsumption patterns need to be addressed at thesame time. Land demand and emissions can be
reduced, for example, by (i) action on food waste and(ii) a shift towards plant-based diets, which results ina net decrease in land demand as grazing and feed
production reduce (Bajželj et al. 2014; IPCC 2019). If
half of all people adopted a plant-rich diet and foodwaste was halved, this could produce an emissions
reduction of 1.8 GtCO2e per year (Roe et al. 2019), as
well as freeing land to deliver nature-based solutions.
One radical scenario suggests that a transition awayfrom animal agriculture could happen naturally, as
animal protein sources are replaced with cheaper
synthetic protein (Arbib, Dorr and Seba 2021).
Solutions that Manage Ecosystems
The potential contribution of different sustainable
management options varies among the studies.
Options with the largest potential include Natural
Forest Management, which envisages reduced
impact logging and longer timber harvest cycles innatural forests that are under extractive management;
and agricultural options, such as agroforestry(Trees in Agricultural Lands) and Cropland Nutrient
Management to reduce nitrogen dioxide emissions,as well as actions that increase carbon stocks
in soils, such as Conservation Agriculture andBiochar. Girardin et al. (2021) are unusual in seeing
a much greater potential for agroforestry than forreforestation; this is consistent with remotely sensed
analysis of the potential for trees to be added toagricultural lands (Chapman et al. 2020). Agroforestry
is indeed a popular option among tropical treeplanting organizations (Martin et al. 2021).
Nature-based solutions that better manage
agricultural land will often increase productivity at
the same time as yielding climate benefits, further
contributing to reduced land conversion pressure.
However, given that a key feature of nature-based
solutions is a net gain to biodiversity and humanwell-being, not every instance of improved land
management will count as a nature-based solution.
For example, biochar involves adding charcoal to
the soil, to improve soil quality and fertility and alsoenhance carbon storage. Biochar can be considereda nature-based solution only when the overall
impact of producing, harvesting and using the12Roe summary 2050

Roe options 2050

Roe summary 2030

Roe options 2030

McKinsey summary 2030

McKinsey options 2030

Girardin summary 2030 & 2050

Girardin options 2030 & 2050

Griscom summary 2030 & 2050

Griscom options 2030 & 2050

0

1

2

3

4

5

6

7

8

9

10

11

12

13

Annual mitigation potential (GtCO2e)
Protect

P: Avoided Forest Conversion

M: Fire Management

M: Grazing - Animal Management

Manage

P: Avoided Grassland Conversion

M: Biochar

M: Grazing - Optimal Intensity

RestoreP: Avoided Peatland Impacts

M: Trees in Agricultural Lands

M: Grazing - Legumes in Pastures

P: Avoided Coastal Wetland Impact

M: Cropland Nutrient Management

M: Mixed Options

M: Natural Forest Management

M: Grazing - Improved Feed

R: Reforestation

M: Improved Plantations

M: Conservation Agriculture

R: Coastal Wetland Restoration

M: Avoided Woodfuel Harvest

M: Improved Rice Cultivation

R: Peatland Restoration

Figure 2: Estimates of the potential of nature-based solutions through time vary. Showing Protect (P),Manage (P) and Restore (R) summaries and response options(Sources: Griscom et al. 2017 (mitigation <US$ 100/tCO2e); Girardin et al. 2021 (<+2°C scenario); McKinsey &Company 2021 (practical mitigation); Roe et al. 2019 (1.5°C wedges) (nature-based solutions only)).
Options mapped onto Griscom typology where possible; the McKinsey figure for avoided forest conversion
also includes avoided peatland impacts.

13biomass feedstock is beneficial to biodiversity. It
is critical to avoid degrading natural ecosystems
to source feedstock for charcoal. In the synthesis
studies, this risk is minimized by restricting biochar
to using crop residues.
Governments can support nature-based solutions
in agriculture in several ways: by repurposing
agricultural subsidies to encourage sustainable
management practices, by supporting extension
programmes to provide training, and by ensuringthat farmers have secure tenure. Land holders
can be resistant to or incapable of embracing
nature-based solutions due to various constraints.
Although vulnerable to climate change impacts,
farmers may: lack the human, technical or financial
resources to adopt innovations; be unable to perceive
the advantages in the long-term; have farming
structures that are not conducive to new practices;
exist in a policy framework that does not incentivize
the change (Pagliacci et al. 2020); and/or beunderstandably reluctant to risk changing practices
underpinning their livelihoods without persuasive
proof of concept. Furthermore, while women andmen are jointly responsible for the management ofagricultural ecosystems and food production, formal
and informal land rights in developing countries
can be skewed in favour of men. Legislation andcustomary practices that prohibit women fromowning land or limit their freedom to claim andprotect their assets need to be addressed to give
women the security to plan for the long term
(United Nations 2013; Doss et al. 2018).
Solutions that Restore Ecosystems
As net CO2 removals (‘negative emissions’) areenvisaged in all IPCC scenarios that limit global
warming to +1.5°C, ecosystem restoration isan essential complement to protecting intact
ecosystems. Some guiding principles have been
established under the United Nations Decade on
Ecosystem Restoration, drawing on a wide range ofexisting guidance, and emphasizing that restoration
with a mitigation objective will only be successful inthe context of a wider transition towards a naturepositive, net zero economy (Food and Agriculture
Organization of the United Nations [FAO] 2021).
Options that Restore ecosystems can take many
years to reach their full potential, as carbon stocks
accumulate and contribute to mitigation overdecades to centuries. Drained peatlands are a
special case, as the principal aim in restoring theirhydrology is to halt the ongoing emissions fromoxidation of their organic soils and reduce the riskof fire, rather than to increase carbon sequestration.

Any accumulation of additional carbon stocks byrewetted peat soils is very gradual and not typicallyfactored into mitigation potential calculations.
Reforestation encompasses a range of practices. In
general, natural regeneration is a more cost-effective
approach than planting (Crouzeilles et al. 2020),
delivering more resilient, biodiverse forests (Chazdon
and Uriarte 2016). Planting results in more rapid
absorption of CO2 over the first twenty years (Bernal,
Murray and Pearson 2018). Under IPCC definitions,‘reforestation’ is carried out on lands which havebeen forested at some point in the previous 50
years, while ‘afforestation’ involves creating a forest
on other non-forested lands (Penman et al. 2003).
If these lands were forested more than 50 years
ago, afforestation may function as a nature-based
solution, but the term is often used to describe
afforestation of natural grasslands, wetlands orsavannas, often with monocultures. While thispractice can contribute to climate change mitigation,
it is often harmful to biodiversity (Pörtner et al. 2021)
and is therefore not seen as a nature-based solution.
Across most studies, Coastal Wetland Restoration
and Peatland Restoration have a smaller role to playin mitigation than Reforestation. Drained peatlands
emit some 1.91 (0.31–3.38) GtCO2e per year (Leifeld
and Menichetti 2018). For peatland restoration, themost optimistic of the synthesis studies combined
agricultural land values with this emissions estimate
to calculate a mitigation potential of around 1 GtCO2e
per year (McKinsey & Company 2021).
As with options to Protect and Manage ecosystems,
ecosystem restoration requires the right enabling
conditions to be realised at scale. The businesscase for restoration can be difficult for land holders,with returns usually accumulating only over the longterm. This makes it harder to cover the up-front
costs, which may include the opportunity costs oflost agricultural revenue if land is being restoredfrom productive use to a more natural land cover,and the costs of the restoration intervention itself.
Governments can help by putting policies in place toincentivize ecosystem restoration, offering rewards
for the public goods delivered; for the Manage
options, governments can improve the security ofland tenure to facilitate long-term planning (Sewell,
Bouma, and Esch 2016).

14

3.4 Further nature-based solutions could be possible in marine ecosystems
In addition to the nature-based solutions includedin the synthesis studies, there are other possible
options that so far lack sufficient information toallow the global potential to be quantified. Several ofthese are found in coastal and marine ecosystems.
On the sea floor, protection of marine sediment fromindustrial trawling and dredging could prevent 0.58
to 1.47 GtCO2 from being released into the watercolumn each year (Sala et al. 2021). However, we
would need to know how much of this CO2 reaches
the atmosphere to quantify the mitigation potentialof reducing the area trawled each year (currently 4.9
million km²). As a precautionary measure, preventionof trawling in areas of high-carbon sediment along
the continental shelf8 would safeguard these carbon
stocks from disturbance (Atwood et al. 2020). Deepsea mining may represent a further future threat
to carbon stocks in benthic sediment and should
therefore also be avoided.
None of the synthesis studies include an estimate
for protection of seaweeds, although they form themost widespread of coastal ecosystems, covering
perhaps 3.5 million km² and do sequester carbon
through sediments drifting to the seafloor. As there isno estimate of the rate of loss of seaweed habitats,
it is not yet possible to estimate the impacts on
their biomass and sequestration functions (HoeghGuldberg et al. 2019).
Seaweed aquaculture or ‘ocean afforestation’ hasbeen proposed as a means to sequester carbon bycontributing to ocean sinks, while also providing a
resource for other response options as it can be used
as a source of biomass for energy production, as analternative fertiliser, or a livestock feed supplement
to reduce enteric methane emissions (N’Yeurt etal. 2012; Duarte et al. 2013; Hoegh-Guldberg etal. 2019). Potential multiple benefits of seaweedfarming include improving water quality in polluted
and low-oxygen areas, at a minimum cost of US$
71/tCO2 (Froehlich et al. 2019). However, analysis ofan algal bloom in the Great Atlantic Sargassum Belt
concluded that after accounting for knock-on effects
elsewhere in the ecosystem, seaweed farming could
represent either a sink or source of CO2 (Bach et al.
2021). Albedo effects were very uncertain, but could
boost the mitigation impact. Careful investigation of
the overall impacts of seaweed aquaculture is stillneeded before this can be proposed as a large-scale
mitigation activity.

Protection and restoration of marine fauna (fishand mammals) could be another response option
for climate change mitigation. By reducing the
population size and changing the demographic
structure of a wide range of species, fishing also
contributes directly to changes in marine carbon
stocks and sequestration. The net outcome forcarbon is not well understood due to the intricate
ecological interactions involved. Carbon is stored in
the living biomass of fished species, and fish also
contribute to the downward flux of carbon throughfaecal pellets, estimated at 1.5 ± 1.2 GtC per year
(Saba et al. 2021). Fished species can have a rangeof roles in maintaining carbon sink potential (e.g.
predation of grazers, reducing algal blooms andmaintaining water quality) and their removal can havetrophic cascade effects that differ in carbon impact
depending on species and ecosystems (Martin etal. 2021). Phytoplankton and krill may have declined
in response to the missing nutrient mixing functionof hunted-out whales (Roman et al. 2014). However,while stocks of marine biomass have been depleted
by whaling and fishing, some may have been
replaced in the form of other species, responding to
reduced predator pressure or decreased competition
for resources. It is therefore difficult to properly
assess the net carbon storage potential of restoring
marine vertebrate populations. We do know thatwhen carcasses of whales and large fish sink to theocean bed, there are long-term deposits of carbon.
A conservative estimate of the annual mitigation
potential of these deposits from fully restored
populations of baleen whales is only 0.0006 GtCO2
per year, and of course it would take some time forpopulations to return to their original levels (Pershing
et al. 2010). Similarly, sequestration by the sinking
carcasses of large marine fish (tuna, mackerel,billfish and shark) is estimated at 0.08 GtCO2 from1950 to 2014 (Mariani et al. 2020). However, thisdata offers only a very narrow window on the roleof marine species in the carbon cycle, and there is aneed for further research and modelling in this area.

8 “…organic-rich coastal sediments along the continental shelf that experience high sedimentation rates and rapid oxygen depletion with depth
are hypothesized to be the most sensitive to disturbances”(Atwood et al. 2020. p.6)

15

3.5 How much mitigation can we expect from nature-based solutions?
Across the syntheses, the total mitigation potentialof options to Protect natural ecosystems fromconversion is fairly consistent, with a range from 3.4
GtCO2e at 2030 to 4.6 GtCO2e at 2050 (Figure 3).
There is a strong consensus that Avoided Forest
Conversion holds the greatest mitigation potential,
because of the extent of forest that continues tobe lost and the immediate benefits of retaining
existing forest compared to waiting for new forest
to grow. Preventing deforestation avoids a pulseof carbon emissions, which would take years torecover if the same site were then reforested. As
the synthesis studies have been refined throughtime, estimates of the overall potential from options
to Restore ecosystems have decreased, especiallyfor reforestation, while still remaining substantial.
Estimates for the potential mitigation benefits from
options that Manage ecosystems are very variable,
being influenced by the number of response options
included and assumptions about how fast they canbe scaled up.

Annual mitigation potential, (GtCO2e)

When comparing across different ecosystems,
forests predominate, typically representing 62 percent (58-65 per cent) at 2050 of the annual mitigation
potential across studies (Figure 2). Response
options based in croplands and grasslands, including
agroforestry, provide the second highest contribution
in the majority of the synthesis studies, around 24 percent at 2050 (22-28 per cent). In addition, although
the Fire Management option includes fire control
practices both for forest and savanna, these studies
focus entirely on forest. Given the relatively small
global area of degraded and threatened peatlands,
their potential contribution to mitigation is very

high, 10 per cent of the total at 2050 (9-11 per cent).
Although peatlands overlap with forest, grasslandand cropland, by focusing on their organic soil
carbon the synthesis studies minimize any overlap in
the calculation of potential. Finally, coastal wetlands(conservation and restoration of mangroves, salt
marshes and seagrasses) represent around 4 percent at 2050 (3-4 per cent) of the total mitigation
potential. In the future, nature-based solutions inmarine ecosystems may further add to this potential.
The synthesis studies reviewed here identify astriking range of total mitigation potential, fromaround 5-11.7 GtCO2e at 2030 to 10-18 GtCO2e at
2050. The studies vary in their assumptions about
how quickly different types of nature-based
solutions can be implemented and financed on alarge scale, and the relative potential of different
solutions (Figure 2).
Some studies concentrate on CO2 alone, whileothers factor in the potential for reducing emissionsof other greenhouse gases. As will be discussed
below, robust safeguards are needed to ensure thatnature-based solutions live up to their bold promise
to deliver multiple societal benefits. All forms of
mitigation need to be implemented at theirmaximum capacity if we are to limit global
temperature rise to no more than 1.5°C. The timerequired to ensure that new nature-based solutions
are properly planned and implemented with inclusive
governance means that by 2030 the lower end of thisrange (5 GtCO2e) may be the most realistic estimateof that capacity, scaling up to at least 10 (maximum18) GtCO2e by 2050.

12
10
8
6
4
2
0

Griscom 2030 & 2050
CoastalGirardin 2030 & 2050
ForestMcKinsey 2030

Roe 2030

Roe 2050

Grassland and Agriculture

PeatlandFigure 3: Global mitigation potential is spread across ecosystems, with all studies concluding that actions inforest have the greatest total potential(Sources: Griscom et al. 2017; Girardin et al. 2021; McKinsey & Company 2021; Roe et al. 2019)
The McKinsey ‘forest’ figure includes avoided peatland impacts, but not peatland restoration.

16

4

Nature-based solutions offer multiple benefits

A major attraction of nature-based solutions as a
strategy for climate change mitigation is that they
can deliver multiple benefits. These benefits include
retained and restored ecosystem services fromforests, croplands, grazing lands, wetlands and othercoastal ecosystems that support human healthand well-being (Anderson et al. 2019), as well as
biodiversity conservation and sustainable livelihood
development. Well-designed nature-based solutions
can also improve human resilience, helping people
to face the challenging impacts of climate change.
Nature-based solutions can increase our capacity toadapt to those impacts of climate change that will
still be present in a net zero world, reduce exposure
to climate-related risks such as flooding and lower
the sensitivity of human communities to climatechange and shocks, for example by diversifying
income (Seddon et al. 2020).
Similarly, nature-based solutions developed with afocus on other objectives, such as Ecosystem-based
Adaptation, can deliver climate change mitigation
benefits (Chausson et al. 2020). Nature-based
solutions focused on food security in farmlands can,likewise, provide a climate dividend (for disasterrisk reduction, adaptation and mitigation) whileconserving water and biodiversity (Miralles-Wilhelm
2021). Nature-based solutions for water security
can similarly yield additional social, economic andenvironmental benefits, including for climate change
mitigation and adaptation (United Nations World
Water Assessment Programme/UN-Water 2018).
If planned well, with considerations for those left
furthest behind, these benefits will improve the livesof women, indigenous peoples, poor farmers andlocal communities whose livelihoods and well-being
are closely tied to natural resources (UNEP 2021b).
It has already been noted that Avoided Forest
Conversion and Reforestation make up a substantial
part of the global potential for mitigation fromnature-based solutions. Natural and planted forests
cover 31 per cent of the terrestrial area worldwide(FAO and UNEP 2020). Protecting and restoring large
tracts of forest can be especially beneficial. Forests
interact with carbon, water and energy cycles indifferent ways, generating large parts of the Earth’s
rainfall through evapotranspiration, which can betransported over long distances in ‘flying rivers’(Schwarzer 2021). But the value of forests goes well

17

beyond their well-known roles in climate change
mitigation and biodiversity conservation. Globally,an estimated 880 million people collect fuelwood or
produce charcoal from forests and over 90 per centof the extreme poor rely on forests for at least part oftheir livelihoods (FAO and UNEP 2020). Cookstoves
with improved combustion efficiencies compared
to traditional stoves or fires use less fuelwood andcharcoal (Urmee and Gyamfi 2014). This saves
time and labour gathering fuel, a burden which
often falls upon women and children, as well as
benefiting women’s health through reducing indoor
air pollution. Adopting improved cookstoves is themeans of implementation for the Avoided WoodfuelHarvest response option of Griscom et al. (2017), andfeatures in several developing countries’ NDCs.
The UNFCCC encourages forest-based nature-based
solutions through its REDD+ framework, which covers“reducing emissions from deforestation and forest
degradation and the role of conservation, sustainable
management of forests and enhancement of forest
carbon stocks in developing countries” (UNFCCC
2021). REDD+ can yield non-carbon benefits
including biodiversity conservation, enhancementof forest ecosystem services, and socio-economic
developments including poverty reduction, genderequality and women’s empowerment, and promotionof an economy supported by sustainable forest
management. In applying the safeguards requiredby the UNFCCC, REDD+ should deliver theseenvironmental and social benefits, ensure the rights
of indigenous peoples and local communities andavoid or mitigate relevant social and environmental
risks. For example, agroforestry is often includedin the scope of REDD+ and can deliver a range ofenvironmental and social benefits. Developing
agroforestry within existing perennial crop
plantations over seven West African countries could
absorb 0.14 GtCO2 per year over twenty years, as wellas connecting forest remnants, providing fuelwood,
improving soils, protecting crops against climate
extremes and enhancing local food and energy
security (Tschora and Cherubini 2020). In an urban
context, forests and parks can contribute to coolingcities, mitigating flood risks, and enhancing healththrough better air quality and provision of leisurespaces (European Environment Agency 2021).

Table 2 describes the multiple benefits delivered by
selected nature-based solutions. It brings together
three existing reviews of these benefits (MirallesWilhelm 2021; Seymour and Langer 2021; World
Economic Forum [WEF] 2021) and complementarystudies. The ecosystem service benefits shown willoften ultimately improve the resilience of people
and ecosystems to climate change, and thus also
represent adaptation benefits. The delivery of thedifferent benefits is classified qualitatively into low,
medium and high levels. For a given nature-based
solution, the benefits may vary depending on how
and where the nature-based solution is delivered,e.g. different levels of management intensity in the
Natural Forest Management response option.
Table 2 can be used to shortlist valuable naturebased solutions approaches for different
circumstances. It can be seen, for example, that justas avoided loss of natural habitats is the most rapid
route (per hectare) to climate change mitigation
impact, retaining the threatened biodiversity andecosystem services in these places is a faster route
to social and environmental benefits than waiting for
habitat restoration to take effect.

18

Socioeconomic benefits

Environmental benefits(often feed into adaptation benefits, including through improved resilienceof natural, seminatural and modified ecosystems)

Nature-based solutions for climate change mitigation

Water quality Reduced risksof extreme
eventsBiodiversity
conservation

Climatestability

Soil health

Avoided Forest
Conversion

+++

+++

+++

+++

+++

+++

+++

Reforestation++/++++++++++/+++++++/++++++

Improved Plantations

+/++

+++

+

+

++

+++

+

Natural Forest
Management

+/++

++

+/++

+

++

++

Conservation
Agriculture(cover crops)

+

++

++

++

Trees in Croplands

++

++

++

+/++

++

+++

Avoided Peatland
Impacts

+++

+++

+++

+++

+++

+++

+++

Peatland Restoration++++/++/+++

++

+++

+++

+/++/+++++

Avoided Coastal
Impacts

+++

+++

+++

+++

+++

+++

+++

+/++/+++

+++

+++

+++

+++

Biodiversity andecosystem services

Coastal Restoration+/++/+++ +/++/+++

Food and/or Culturalenergyservices andprovision
health security+++

Table 2: Multiple benefits of selected nature-based solutions for climate change mitigation(qualitative scale: +++ high benefits; ++ medium benefits; + low benefits)(Sources: Miralles-Wilhelm 2021; Seymour and Langer 2021; WEF 2021; and others detailed in supplementary table.)
Further details on the scale of benefits available can be found in a supplementary table, at: http://wcmc.io/nbs-mbs; lists ofnature-based solutions and benefits are not exhaustive.

19

5

Social and environmental safeguards

To ensure that nature-based solutions live up to
their promise to deliver on multiple local and global
agendas over the long-term, robust safeguards areneeded to guide their design and implementation.
Safeguards can help to manage social andenvironmental risks as well as to achieve multiple
benefits that strengthen the case for scaling
up. REDD+ already has this type of safeguards
framework, agreed under the UNFCCC, but there
is not yet an equivalent for non-forest ecosystems(Seddon et al. 2020). Some countries are alreadychoosing to apply REDD+ safeguards beyond forests,
for example, Honduras, which is working on a single
framework for all climate change projects andprogrammes. Safeguards for nature-based solutions
for mitigation can also build on those detailed in
the guidelines for ecosystem-based approaches
for climate change adaptation and disaster risk
reduction adopted under the CBD (CBD 2018;
Secretariat of the Convention on Biological Diversity2019). Meanwhile, IUCN has consulted widely on its
Global Standard for Nature-based Solutions (IUCN
2020a; IUCN 2020b) and is working with partners
to integrate this into existing certification schemesthat could then be used to demonstrate that a given
intervention meets the standard (IUCN 2021).
Nature-based solutions provide benefits forbiodiversity and human well-being while addressing
other societal challenges. However, discussions
under the CBD have highlighted specific concerns.
Some indigenous peoples and civil society groups
have argued against any form of carbon trading,being concerned not only that market-oriented
nature-based solutions may involve privatizationof natural resources held in common, with somestakeholders benefiting at the expense of others, butthat offsets would be used to delay action to reduce
emissions (Tugendhat 2021). There is a concernthat the need to engage indigenous peoples andlocal communities in decision-making will be not betaken seriously, but reduced to a box-ticking exercise(Seddon et al. 2021). Many of these concerns
are addressed under the IUCN Global Standard,
which expands on the IUCN definition of nature-

based solutions in a way that reflects existing CBD
Decisions. For example, the principles of the CBD’s
Ecosystem Approach – that ecosystem management
should be done “in a fair and equitable way”, pursuing
objectives which “are a matter of societal choices”
and “involve all relevant sectors of society” (CBD2007) – are addressed in the Standard, which interalia calls for involving stakeholders at all stages,
upholding the right of indigenous peoples to ‘free,prior and informed consent’, prioritizing the mostpressing societal challenges according to rightsholders and potential beneficiaries, identifying thebenefits and costs of each solution and ensuring
these are equitably shared amongst stakeholders.
Safeguards are also needed to ensure the climatechange mitigation benefits of nature-based solutions.
UNFCCC discussions are focused on its primaryobjective to stabilize “greenhouse gas concentrationsin the atmosphere at a level that would prevent
dangerous anthropogenic interference with theclimate system” (UNFCCC 1992, p.9). Safeguards
are needed to address ‘leakage’, ‘additionality’,permanence and double-counting . When naturebased solutions are applied over small scales andin a context of continuing land demand, ‘leakage’(displacement of the original land-uses) can undosome of the carbon savings made. To ensure‘additionality’, the solutions must deliver carbon
benefits compared to the business-as-usual situation,
without the intervention. If the achievements ofnature-based solutions are reversed through humanaction or even as a result of climate change itself,
permanence questions are raised around whether
there have indeed been net emissions reductions.
If carbon credits from nature-based solutions
are traded and used for offsets, without reliableaccounting systems, there is a risk of the mitigation
benefit being over-stated, lessening pressure to
reduce emissions elsewhere. While safeguards forleakage and permanence are in place for REDD+, therules intended to avoid double-counting and ensure
additionality within international emissions trading
under Article 6 of the Paris Agreement are still undernegotiation (Asian Development Bank [ADB] 2020).

20

These various issues must be tackled in safeguards
and in carbon accounting, both for nature-based
solutions and other response options.
As well as helping to ensure that nature-based
solutions for mitigation are genuinely beneficial
for people and nature, adopting appropriate
safeguards makes it clear that, as noted earlier,
not all land-based response options for climatechange mitigation should be counted as naturebased solutions. Options that enhance carbon sinks
without regard to biodiversity conservation needs,
plant trees in peatlands or natural grasslands whose
carbon stocks are vulnerable to disturbance, or plantlarge areas of monocultures for biomass energy,
are unlikely to qualify as nature-based solutions. To
secure societal benefits and avoid risks may requirean analysis of social and cultural factors that resultin exclusion and discrimination based on genderor other factors. Top-down land-use planning thatblocks the participation of vulnerable groups such21

as women, youth, indigenous peoples and local
communities is not likely to yield a set of proposedsolutions that meets their needs. Moreover, suchplanning could well present risks to land rights,
food security and ecosystem services that
communities depend upon. If governments areable to apply or adapt the safeguard approaches
developed for initiatives such as REDD+ toaccommodate other nature-based solutions, this
could go a long way towards reducing these socialand environmental risks.

6

Increasing support for nature-based solutions

6.1 Nature-based solutions in national mitigation commitments
The Paris Agreement offers a concrete opportunity
to scale up nature-based solutions for both climatechange mitigation and adaptation, in that it requires
all countries (Parties) to submit their NDCs in supportof the goals of the Agreement. The Agreement’s
Article 6 also allows for Parties to finance mitigationin other nations, both through market and nonmarket approaches. In the NDCs, Parties set out their
mitigation commitments as well as (in most cases),
their adaptation priorities and targets.
As well as expecting that NDCs are updated at least
every five years with progressively more ambitious
pledges, the Paris Agreement invited countries to
set out “long-term low greenhouse gas emission
development strategies” (2015, p.4). These strategies
may include a long-term vision to guide the definitionof successive NDCs, including goals for both
mitigation and adaptation, such as the target date
for achieving net zero ambitions across sectors.
The role of nature-based solutions in NDCs has
increased through time. In 2017, only 38 of 160
NDCs assessed specified land-sector mitigation
contributions (Griscom et al. 2017). By 2019, themajority of NDCs included actions that could beinterpreted as nature-based solutions, but theselargely lacked quantifiable targets and were morecommon in developing than developed countries(Seddon et al. 2019). More than two thirds of NDCs
appeared to refer to mitigation in forests, although
they may not all involve nature-based solutions.
Only 20 per cent included quantifiable targets forforests, and only 8 per cent expressed these targets
in tCO2e. Ecosystems other than forests wereless well represented. In the NDCs of developing
countries, targets are often presented as conditional
on international finance. By 1 May 2021, 55 Parties
had submitted updated or revised NDCs. Of these,
44 referred to nature-based solutions for mitigation,with an increasing number including quantifiabletargets (Bakhtary, Haupt and Elbrecht 2021). The
number of NDCs that referenced wetlands or coastal
ecosystems also increased.

Elbrecht 2021) as well as selected others. In
selecting additional NDCs for review, we focusedon those covering a large geographical area andincluding land-use, land-use change and forestry(LULUCF) or agriculture in their sectoral scope,according to the Institute for Global Environmental
Strategies (IGES) database (IGES 2021). We
assessed whether each NDC included actions
to Protect, Manage or Restore each of four
broad ecosystem types, noting that many usedbroad language that made it difficult to specify
a category (Figure 4). Some NDCs continue tomake commitments on tackling emissions fromthe LULUCF sector without being explicit that thisinvolves nature-based solutions or specifying targets
for particular ecosystems. The European Union
notably includes a stringent provision on LULUCF
becoming net zero, making individual member
states responsible for determining how this will
be implemented – commitments of this nature do
not feature in our summary. Due to huge variationin the way that actions are described within NDCs,
we did not attempt to summarize the intended
impact of the actions. Overall, there were slightly
more commitments to Manage and Restore thanto Protect ecosystems. Forest-based options were
overwhelmingly the most common, followed bygrassland and agriculture, coastal ecosystems andfinally wetlands.

To further investigate the types of nature-based
solutions included in current NDCs, we reviewed
summaries of NDC content from the United
Nations Development Programme (UNDP) (UNDP,
unpublished) and WWF-UK (Bakhtary, Haupt and22Number of NDCs including Protect, Manage or Restore response options

Protect
Manage

0

5

10

15

20

25

30

35

40

45

50

55

60

65

RestoreForestGrassland & Agriculture

Africa (n=37)

CoastalWetlands incl. peatlands

ForestGrassland & Agriculture

Americas (n=22)

CoastalWetlands incl. peatlands

ForestGrassland & Agriculture

Asia (n=25)

CoastalWetlands incl. peatlands

ForestGrassland & Agriculture

Europe (n=9)

CoastalWetlands incl. peatlands

ForestGrassland & Agriculture

Oceania (n=7)

CoastalWetlands incl. peatlands

Figure 4: Nature-based solutions in NDCs more often focus on forest than on other ecosystems(Source: own summary based on a review of 100 NDCs)
Protect, Manage and Restore actions counted once per ecosystem; n=number of NDCs reviewed per region.

23

6.2 Private sector commitments on climate change mitigation
Achieving the mitigation promises made in NDCs
will require countries to adjust regulation, taxes andincentives to encourage private sector action. Nature
not only has a place in NDCs, but also in private
sector climate change mitigation strategies. The
United Nations ‘Race to Zero’ campaign has brought
together net zero initiatives that represent at least
3,067 businesses and 173 large investors, alongside
cities, regions and universities. All have committed
to achieving net zero emissions by 2050, with somemaking more ambitious commitments to absolute
zero emissions, or to becoming ‘climate positive’,absorbing more greenhouse gases than they emit.
Interim targets for the coming decade are required ofmembers9 (United Nations [UN] 2021).
Nature-based solutions can be used in corporate
net zero strategies in different ways (Pineda, Chang
and Faria 2020): by reducing land-based emissions
that companies are responsible for (e.g. fromdeforestation in their supply chains); as a meansof ‘compensating’ for ongoing emissions as thecompany moves towards net zero; and to ‘neutralize’
any emissions that remain when the net zerodeadline is reached (see section 8).

9 These targets should reflect “maximum effort toward or beyond a fair share of the 50% global reduction in CO² by 2030” to limit warming to
1.5° C, in line with the IPCC Special Report on Global Warming of 1.5°C (UN 2021, p.2)

24

6.3 Partnerships for nature-based solutions
Collaboration between governments, corporates,
scientists and civil society is key for the successful
deployment of nature-based solutions at scale. Since
2017, a number of collaborative initiatives havebeen founded to promote nature-based solutions indifferent ways, often with an emphasis on providing
finance through carbon credits. The Natural Climate
Solutions Alliance, convened by the WEF and WBSCD,
is focused on facilitating discussion between
suppliers, buyers and other parties interested incarbon credits from nature-based solutions (WEF
2021). The Alliance provides guidance to businesses
on including nature-based solutions within theirclimate strategies, and on the use of carbon credits
from credible, safeguards-compliant nature-based
solutions to neutralize or compensate for theiremissions (Natural Climate Solutions Alliance[NCSA] 2021). The Nature4Climate partnership,
hosted at The Nature Conservancy (TNC), advocatesand communicates the value of nature-based
solutions for climate change. It comprises 16
conservation, multilateral and business organizations,
including the CBD, IUCN, UN-REDD Programme,
UNEP, UNDP, WBCSD, WWF and the World Resources
Institute (WRI).
Other initiatives aim to foster particular types ofnature-based solutions. Jurisdictional approaches
account for changes in ecosystem carbon overentire jurisdictions – which may be provinces, oreven countries – rather than within a single projectsite. One advantage of this approach is that it
eliminates the risk of leakage being unaccounted
for within the jurisdiction. For forests, the Green
Gigaton Challenge, initiated in 2020 by the UNREDD Programme together with several non-profit
organizations, aims to support governments in theirefforts to halt deforestation (Edwards 2021). The
challenge is to fund 1 GtCO2e of jurisdictional-scale
emissions reductions per year by 2025, with theintention of demonstrating that both supply anddemand can function at scale. The LEAF Coalition,
launched in 2021, brings together government (UnitedStates of America, United Kingdom and Norway)
and private sector partners with a similar objectiveof mobilizing both private and public sector funds toProtect tropical forests at scale. The Green Gigaton
Challenge focuses on making the case for investment
in nature, promoting minimum donor-funded prices
for carbon results, and private sector demand at
higher prices. The LEAF Coalition has establisheda new framework for results-based payments
for REDD+. A call for proposals to supply future
emissions reductions received applications from 30
jurisdictions, of which 21 have passed the first stage.
Many large companies have joined the coalition
with an interest in participating in transactions. Both25

initiatives involve the non-profit Emergent Forest
Finance Accelerator, which was established to act as
an intermediary to sell tropical forest carbon credits
to the private sector.
LEAF places restrictions on both buyers andsuppliers of credits. Suppliers must meet theprovisions of the ART-TREES standard (Architecture
for REDD+ Transactions - The REDD+ Environmental
Excellence Standard) to measure emissions
reductions performance and report on how they
are implementing the UNFCCC’s safeguards. ARTTREES is especially focused on transparency andenvironmental integrity, establishing provisions onleakage, permanence, uncertainty calculation andavoidance of double counting. LEAF buyers may
be countries (‘sovereign contributors’) or private
sector buyers that have committed to strong
decarbonization targets for their own emissions,
including net zero targets by 2050. To connect thetwo types of buyer, LEAF offers four transaction
pathways (LEAF Coalition 2021): (1) a traditional
donor pathway, in which sovereign contributors
fund emissions reductions that the supplier country
retires and may include in its NDC accounting; (2)the same approach, with a private sector buyer;(3) a market transaction in which the private
sector buyer takes title to the emissions reduction
credits, while the supplier country still includes theunderlying mitigation in accounting for its NDC;
(4) a transaction in which the private sector buyer
takes title of the credits, and can use these towards
its compliance targets, and the supplier country
makes a ‘corresponding adjustment’, not counting
the mitigation towards its NDC. Final decisions on
the rules for international transfers of mitigation
outcomes under Article 6 of the Paris Agreement may
influence which of these pathways are most viable in
the future (ADB 2020).
In 2021, the European Carbon+ Farming Coalition was
launched as part of a larger effort to transform global
food systems, under the auspices of the WEF. It aims
to promote regenerative and climate-smart practices
to better Manage Europe’s farmlands, contributing
to the decarbonization of the European food system,
healthier soils and more resilient farms. In the marine
realm, the Blue Natural Capital Financing Facility
managed by IUCN became operational in 2018. It
is helping to Protect, Restore and Manage marine
ecosystems by financing climate change mitigation
and adaptation efforts that meet its Positive Impacts
framework, for example, generating carbon credits
from seagrass ecosystems in Kenya’s Vanga Bay.
Similar initiatives in the land-use finance space
include Indonesia’s Tropical Landscapes Finance
Facility and the Rabobank-led Agri3 fund.

7

Financing needs

Nature-based solutions receive a small proportionof existing public and private climate-mitigation
financing. Finance for climate change mitigation
flows from public funds, development financeinstitutions, state-owned enterprises and financial
institutions, private corporations and even private
individuals investing in low carbon technologies suchas electric cars (Climate Policy Initiative [CPI] 2020).
Overall, only 3 per cent of all climate finance (formitigation or adaptation) in 2017–2018 was directed
towards AFOLU and natural resource management,
categories which include some (unknown) proportionof nature-based solutions. Of the US$ 532 billion peryear invested in mitigation, most was for renewableenergy and low-carbon transport. Only 2 per cent wasinvested in AFOLU and natural resource management(CPI 2020). In contrast, the proportion for the muchsmaller pot of adaptation funding was around 16 percent. According to global models, around US$ 2.4
trillion per year between 2016 and 2035 is needed
for supply-side energy system investments alone,
for limiting global warming to 1.5°C (IPCC 2018).
This indicates that the finance currently available fornature-based solutions is far below the level needed,consistent with the broader findings of the State of
Finance for Nature report (UNEP 2021a).
Finance for nature and nature-based solutions has
been identified as one of eleven public financepriorities by the COP26 Presidency, which called for
an increase from both public and private sources(COP26 Presidency 2021). The need is especiallygreat for tropical countries, where the median costof implementing nature-based solutions for climatechange mitigation at US$ 100/tonne, equivalent
to nearly 6 per cent of national GDP, with outliers
up to 46 per cent of GDP (Griscom et al. 2020).
International transfers, whether public or private,
will be needed to support nature-based solutionsin these countries.
Governments can also influence the financing needed
for nature-based solutions by reducing their costs:
transforming subsidies and incentive systems toencourage nature-positive land and sea-use. In 2020,
91 states committed to do just this, in the Leaders’Pledge for Nature, also signed by the President of theEuropean Commission. The Pledge further commits
countries to enhance resource mobilization, scaling
up public and private sector support for biodiversity,
including nature-based solutions.
Even with this additional effort from governments,
if nature-based solutions are to deliver on theirclimate change mitigation promise, all sourcesof finance will be needed, from public to private,
domestic to international (Girardin et al. 2021). A
substantial increase in private sector investment
is needed to complement public funding (Carney
2020; Seddon et al. 2021) including actions withincompanies’ own value chains and as a means ofcompensating for and neutralizing residual
emissions en route to net zero.

26

8

How can offsets play a role?

A debate is underway about the role of emissions
reductions and removals from nature-based
solutions in offsetting emissions from other partsof the economy. While proponents believe that thisapproach can quicken our progress to net zero,
reducing the risk of dangerous climate change, critics
are concerned that offsetting will instead reduce
ambitions for emissions reduction, thus “letting
polluters off the hook”. In addition, it is argued that
excessive confidence in the future potential for
carbon dioxide removals, whether through natural
solutions or nascent technological approaches,
can diminish the perceived urgency of action onemissions (Dyke, Watson and Knorr 2021).
An IUCN survey held between June and September
2021 canvassed views on the use of nature-based
solutions for carbon offsetting, and received 569
responses from a wide range of actors10.
The survey first solicited general views on the use ofnature-based solutions for carbon offsetting. It thenunpacked the conditions under which respondents
felt that this could be acceptable. Over 80 per cent ofrespondents expressed support for the use of naturebased solutions for carbon offsetting purposes,
whether by state or non-state actors. However, 75 percent expressed concern that such use could reduceoverall mitigation ambition or have other harmful
consequences. To address this concern, 93 per centof respondents supported allowing the use of naturebased solutions for carbon offsetting only if certain
conditions were fulfilled, while 7 per cent opposed alluse of nature-based solutions for these purposes.
Respondents were then invited to review 10 possible
conditions, in the form of solution statements.
These aimed to address four thematic categories
of risks: (1) of delay to broader decarbonization of
the economy; (2) of harm to natural ecosystems
and biodiversity; (3) of harm to local communities
and indigenous peoples and (4) of lack of long-term
commitment and quality and integrity assurance.
Overall, there was broad support for the possible

conditions. On average, 69 per cent expressed theirclear agreement with the statements, and 93 per centeither agreed or partially agreed.
The highest support (>80 per cent) was expressed for
conditions establishing that the use of nature-based
solutions for carbon offsetting (i) must support andenhance biodiversity, and should not contribute to theconversion or loss of existing natural ecosystems;and (ii) must ensure full protection of the rights ofindigenous peoples and local communities, cause noharm to them, and assure equitable benefit sharingof any revenues generated through such measures.
These conditions are consistent with the IUCN Global
Standard for Nature-based Solutions.
A high level of support (>70 per cent) was also
expressed for conditions establishing that the useof nature-based solutions for carbon offsetting (i)not act as a substitute for cutting greenhouse gas
emissions or delay wider decarbonization; (ii) be
certified by programmes with robust systems that
can assure high quality, high integrity carbon credits
for nature-based solutions11; (iii) if transacted undervoluntary schemes, be linked eventually to carbon
accounting systems under Article 6 of the Paris
Agreement to avoid double-counting; and (iv) adhere
to the IUCN Global Standard to provide overall
quality assurance.
Over 3000 comments on the 10 possible conditions
were received. For instance, it was highlighted that
although the use of nature-based solutions forcarbon offsetting focuses on climate mitigation perse, these activities need to also include adaptation
and resilience objectives in order to fully contributeto the goals of the Paris Agreement. Likewise, it wasnoted that nature-based solutions interventions must
be appropriate for their areas of implementation,and that beyond the generation of carbon offsets,companies and governments should also havestrict overall policies for stopping deforestation andhabitat conversion. It was commented that specifying
and calculating a price premium for nature-based

10 Respondents included IUCN’s state and government agency members; national/international non-governmental organization (NGO) andindigenous people’s organization (IPO) members; national and regional committees; commission experts; and others from across IUCN’s
statutory regions (Africa, Meso and South America, North America and the Caribbean, South and East Asia, West Asia, Oceania, East Europe,
North and Central Asia, West Europe).
11 I.e. any emission reductions and removals from nature-based solutions had to be real, quantified and verified, with issues of additionality,
leakage, and permanence satisfactorily tracked, addressed, and reported on.

27

solutions carbon offsets would likely require amix of measures, including regulation, incentives,
consumer influence, and adequate measurement
and monitoring systems for the various benefits ofnature-based solutions. It was noted by some that
the IUCN Global Nature-based Solutions Standard
should be used to complement existing carbon
measurement and verification standards andplatforms, to help improve and assure the ecosystemand social integrity of offsetting activities claimed.
Some respondents questioned the need for naturebased solutions carbon offsets generated throughvoluntary schemes to be strictly linked to complianceand carbon accounting systems being set up under
Article 6 of the Paris Agreement.
While further analysis will be conducted by IUCN,
the survey findings are indicative of the views thatcurrently exist within IUCN’s constituencies on themain conditions that are needed to ensure highquality, environmentally and socially responsible
use of nature-based carbon offsetting. Moreover,the findings highlight areas of consensus and of
possible debate.

28

Theme 1: Risk of NbS for carbon
offsets delaying the broader
decarbonization process0%

How to address this risk?
Solution Statements/Recommendations
1.

2.

3.

40%

20%

Agree

60%

100%

80%

Partially Agree

Disagree4%

NbS can be a powerful tool to capture carbon
from the atmosphere, but they are not a
substitute for cutting greenhouse gas (GHG)
emissions and should not be used to delay theprocess of decarbonizing our economies.

76%

NbS for carbon offsetting should be allowed
only after achieving the maximum emission
reductions possible within an company’s/organization’s value chain (scope 1, 2 and 3
emissions), or within a country’s domestic
emission sources, in a manner consistent with
the GHG emissions mitigation hierarchy (i.e.
avoiding and reducing emissions should beprioritized first).

48%

State/non-state actors whose activities,
operations, or value chains generate GHG
emissions from the use of natural resources
should first fully integrate NbS within their own
internal emission reduction targets to minimize
these emissions and other negative impacts on
ecosystems before being allowed to use NbS forcarbon-offsetting

20%

35%

63%

17%

26%

11%

Theme 2: Risk of NbS for carbon
offsets harming natural ecosystems/
biodiversity
How to address this risk?
Solution Statements/Recommendations
4.

5.

Agree

Partially AgreeNbS used for carbon offsetting purposesmust support and enhance biodiversity inaddition to delivering carbon sequestration/
storage outcomes. They should prioritize theconservation of existing natural ecosystems andnot contribute to their loss or conversion.
NbS credits used for carbon offsetting
purposes should command a price premiumvis-à-vis other credits on the account of themultiple co-benefits that NbS provide to people
and biodiversity in addition to emissions
reductions/removals.

2%
86%

54%

Figure 5: IUCN survey responses to possible conditions (solution statements) under which
the use of nature-based solutions (NbS) for carbon offsetting may be allowed

29

Disagree

12%

36%

10%

Theme 3: Risk of NbS for carbon
offsets harming local communities
and indigenous peoples

0%

How to address this risk?
Solution Statements/Recommendations
6.

NbS used for carbon offsetting purposes mustensure full protection of the rights of indigenous
peoples and local communities, cause no harmto them, and assure equitable benefit sharing of
any revenues generated through such measures.

20%

Agree

40%

60%

Partially Agree

80%

100%

Disagree

3%
83%

14%

Theme 4: Risk of lack of long-term
commitment and quality andintegrity assurance
How to address this risk?
Solution Statements/Recommendations
All NbS used for carbon offsetting purposes
should adhere to the IUCN Global NbS Standard
to provide overall quality assurance on theirimplementation on the ground.
8. State and non-state actors using NbS forcarbon offsetting should commit to long-term
purchase agreements to ensure continued
investment in high-quality, high-integrity NbS
carbon credits.
9. State/non-state actors should invest in only
those NbS carbon credits that are certified
by programmes with robust systems that
can assure high quality, high integrity NbS
carbon credits
10. State/non-state actors should invest in NbS
carbon credits from voluntary offsetting
schemes only if these can be credibly andverifiably linked to official carbon accounting
systems set up to deliver compliance under
Article 6 of the Paris Agreement, and are able to
make ‘corresponding adjustments’ as needed.

Agree

Partially Agree

Disagree

4%

7.

71%

66%

25%

26%

8%
5%

73%

22%

73%

18% 9%

Figure 5 (continued): IUCN survey responses to possible conditions (solution statements)
under which the use of nature-based solutions (NbS) for carbon offsetting may be allowed30

As standards and norms surrounding the use ofnature-based solutions, whether as offsets orwithin value chains, continue to develop, companies
can signal demand for high-quality nature-based
solutions and advocate robust rules for offsetting(Seymour and Langer 2021).
The Science Based Targets initiative (SBTi)12 isworking on criteria for companies that wish to set net
zero targets. The initiative aims to reduce confusion
among consumers and stakeholders and to bringmore clarity to corporate commitments (Voluntary
Carbon Markets Integrity Initiative [VCMII] 2021a).
The lack of a single clear definition of net zero for
corporate action means that differences can befound in the way that companies include emission
sources and gases in their target boundaries, scope
and ambition (Pineda, Chang and Faria 2020).
Besides net zero commitments to achieve emissions
reductions in the future, corporate voluntary climate
commitments may include emissions reductions
for current activities, such as carbon neutrality at
the company level, for specific products or services
and also ‘beyond carbon neutrality’, which implies
reducing emissions in excess of current emissions,for example covering historical years (VCMII
2021b). There is an emerging consensus that, firstand foremost, companies must make all efforts to
reduce emissions within their value chain, including
those that they are directly responsible for (Scope
1 emissions), those from energy that they purchase(Scope 2 emissions) and those from other parts of
their value chains (Scope 3 emissions).
SBTi is currently undertaking a public consultation
process and aims to release a corporate net zerostandard in November 2021 (VCMII 2021b). Its
working definition for a net zero company requires
deep decarbonization of value chain emissions in linewith limiting warming to 1.5°C, and the neutralizationof any residual emissions with permanent carbon
removal (VCMII 2021b). It is recognized that this is
a process of transition, and that carbon offsets canbe used to compensate for remaining emissions
as companies put measures in place to eliminate
them. SBTi encourages companies to directly financeinnovative projects and programmes as well aspurchasing high-quality carbon credits during their
net zero transition, to help deliver positive outcomesbeyond a company’s value chain. Companies need
to be explicit about the role of offsets as they

move towards net zero (Carney 2020; Seddon etal. 2021), showing that they are not a means to
avoid emissions reduction, but a means to reduce
emissions more rapidly and finally to ‘neutralize’
unavoidable emissions.
There are differences of view over whether avoided
emissions from natural habitat loss are appropriate
for use as offsets or should be separately funded as
an essential part of achieving net zero emissions.
SBTi’s current draft guidance limits companies
to using removals, not reduced emissions, when
offsetting their own emissions to achieve net zerotargets. That is, their accounting approach considers
that only ‘neutralization’ efforts that remove carbon
from the atmosphere can be used to counteract any
residual emissions that cannot be tackled (VCMII
2021a; VCMII 2021b). As presently formulated, thisapproach limits ‘neutralization’ to nature-based
solutions that Restore or sometimes Manage
ecosystems, thus potentially limiting the scope forthe private sector to scale up nature-based solutions
for climate change mitigation. This position contrasts
with the approach of the ART-TREES standard, which
requires a jurisdiction to show that emissions fromdeforestation and forest degradation are being
tackled before credits can be issued for removals
from reforestation. This latter approach is consistent
with the mitigation hierarchy.
There is a need to develop an infrastructure forscaling up high-quality and functioning carbon
markets, and a set of rules and guidance that allow
funding to be directed towards well-planned naturebased solutions that do not delay the urgently
needed decarbonization (Carney 2020; Seddon et al.
2021), as well as ensuring demand-side integrity, as
seen in the SBTi corporate net zero standard. The
private sector-led Taskforce for Scaling Voluntary
Carbon Markets is consulting on a blueprint for a
voluntary market infrastructure of this type, and aroadmap to implementation (Taskforce on Scaling
Voluntary Carbon Markets 2021). Again, the precise
implementation may be influenced by final decisions
on the rulebook for Article 6 of the Paris Agreement.

12 The Science Based Targets initiative (SBTi) is a partnership between the Carbon Disclosure Project (CDP), the United Nations Global
Compact, World Resources Institute (WRI) and WWF. Building on the momentum of the SBTi, the Science-Based Targets Network (SBTN) is
working to enable companies and cities to set targets for climate and nature. More information can be found at: https://sciencebasedtargets.
org/.

31

9

Conclusion

Nature-based solutions have a vital role to play inmitigating climate change, while simultaneously
providing adaptation and other benefits. We
conclude that at least 5 GtCO2e per year by 2030
and 10 GtCO2e per year by 2050 is feasible, taking a
conservative outlook across the several publishedstudies. The underlying estimates have a wide
range, which reflects the uncertainties regarding
the types of intervention considered, the speed atwhich they can be scaled up, the global willingness
to pay for nature-based solutions, represented byassumptions about the value assigned to climatechange mitigation (US$/tCO2e) and the impact thatstrict adherence to safeguards will have. In the lightof these uncertainties, we can have more
confidence in the estimates at the lower end of
the ranges provided.
However, while nature-based solutions have anecessary role to play, achieving the Paris Agreement
goal will require, above all, a rapid, ambitious andsustained abatement of fossil fuels and otherindustrial emissions, as called for by the latest
science (Pörtner et al. 2021; Seymour and Langer
2021). Without this ambitious action to decarbonize
national economies taken by governments andcorporates and supported by civil society, it will be
impossible to limit global temperature rise to below
1.5°C in the coming years. This would undermine thecapacity of the biosphere/ecosystems to draw down
and store carbon, and likely turn the biosphere into a
net source of greenhouse gases.
Nature-based solutions can be implemented acrossterrestrial and marine ecosystems, although weunderstand far more about the terrestrial response
options. Across ecosystems, the overall mitigation
potential is highest in forests, and then in grasslands
and agriculture, with peatlands and coastal wetlands
representing a very high potential per hectare, but alower overall potential due to their smaller area. This
understanding is broadly reflected in NDCs, whichmore frequently put forward solutions for mitigation
centred on forests, grasslands and agriculture thanfor other ecosystems.
If nature-based solutions are to deliver on thiscontribution to mitigation, then the necessary
safeguards, carbon accounting frameworks andgovernance schemes that have been identified
here need to be in place and strictly enforced.
Moreover, the finance must be available to ensure
delivery. Initiatives such as LEAF and the Green
Gigaton Challenge offer promising ways forward,
at least for forests. A proportion of the necessaryfinance could be delivered through the responsible
use of nature-based solution offsets, provided that
new and emerging frameworks are utilized to ensurethat the achievement of net zero targets is notcompromised and biodiversity and local
communities benefit. These initiatives for forests
should be adapted for use in other systems,
particularly in agricultural lands and degradedpeatlands of all types, to allow nature-based
solutions to be advanced there.
Equitable and resilient nature-based solutions canmitigate climate change while simultaneously
strengthening both ecosystems and communities’
resilience to climate change, promoting biodiversity
conservation and reducing the risk of climate change
feedbacks and impacts (Seddon et al. 2021). We
have an opportunity now, while rebuilding economies
in a post-Covid-19 world, to deploy robust andresilient nature-based solutions. With strategicplanning, evidence-based action, and engagementof local communities, solutions based on nature cancreate jobs and stable livelihoods, and better manage
our food and forestry systems, all while addressing
the urgent challenges of climate breakdown andbiodiversity loss.

32

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