Nature-Based Solutions to Climate Change

IUCN Definition for ‘Nature-based solutions’

Actions to protect, sustainably manage and restore natural and modified ecosystems in ways that address societal challenges effectively and adaptively, to provide both human well-being and biodiversity benefits.

How does the Paris Climate Agreement (2015) recognise the importance of NBS?

It calls on all parties to acknowledge “the importance of ensuring the integrity of all ecosystems, and the protection of biodiversity”; 66% of signatories legally-bound themselves to commit to NBS in their climate pledges.

What is climate change mitigation?

Efforts to reduce emissions and enhance carbon sinks

What do nature-based solutions include?

Avoiding emissions by limiting deforestation and environmental degradation, restoring degraded ecosystems, increasing ecological diversity, changing agriculture management practices.

Which NBS has the most significant contribution to avoided emissions?

Protecting intact forests, wetlands and grasses (4 GT CO₂/yr), managing working lands for crops, grazing and timber (4 GT CO₂/yr), and restore native ecosystems (2 GT CO₂/yr)

What percentage of global CO₂ emissions are attributed to the agriculture, forestry and other land use sector per year?

Fitts, 2025: 21% - land use change is associated with 13% of these emissions.

What is the Bonn Challenge?

The Bonn Challenge (IUCN, 2011) is a global effort involving 56 nations to retore 350 million Ha of degraded land by 2030. This restoration is projected to sequester an additional 1.6 GtC/yr, equivalent to 14% of current emissions. (Dave et al, 2017)

Why is the Bonn Challenge problematised?

These international frameworks focus on the extent rather than the quality of forests which they create. 24 of the countries involved, covering 2/3 of the pledged area, have stated that 45% of the area is slated to become monoculture plantations, and only 34% is given to restoring natural forests. Encouraging the establishment of fast-growing monoculture plantations, including exotics, is done because it maximises short-term carbon sequestration. However, these tree species are highly vulnerable to long-term changing conditions and disturbances, which is especially relevant in light of climate change.

Lewis et al, 2019 - impacts of monoculture plantations on the Bonn Challenge targets

Restoring natural forests over the whole 350m hectares of land could remove 42 billion tonnes of CO₂ from the atmosphere by 2100. Through the current proportion of pledges (34%) to natural forests, this is only 16 billion tonnes. If commercial monocultures of pines and eucalypts were planted across 100% of the pledged area, solely 1bn tonnes of carbon would be sequestered - having a negligible impact on atmospheric CO₂ concentrations, especially if emissions continue at current rates.

Issues with the spatial distribution of the Bonn Challenge - Bond et al, 2019

Targeted areas for the Bonn Challenge are based on global maps of degradation. This erroneously assumes that low tree cover in ancient savanna landscapes where tree cover is reduced by browsing on trees, and several million years of grass-fuelled fires, which means that 100Mha of mostly savanna in Africa have been designated for reforestation. Even at this target, the current growth rate of atmospheric CO₂ would be mitigated by merely 2.7% per year.

Cameroon has pledged converting 12Mha, equivalent to ¼ of the country’s land area; Nigeria’s 32%, and Burundi’s 72%. This represents a major trade-off for land; Nigeria is Africa’s most populated country, estimated to almost double by 2050. Areas at risk of afforestation are currently supporting biodiversity and livelihoods, which would be lost in the local context of the individuals affected. Therefore, top-down actions do not account for local voices, values and knowledge in decision-making, and perpetuate power asymmetries.

Plantation forests are highly vulnerable to severe fires, exacerbated by global warming. Given that tree coverage increases albedo and has a net warming effect on the local area in the short-term, this may increase the arid savanna’s susceptibility to fire. Suppressing grass fires is far easier than plantation fires, and grasslands have higher rates of carbon sequestration belowground (90%), which makes them more stable carbon sinks in fire-prone climates.

What is the cost of the Bonn Challenge?

To nullify the growth rate in atmospheric CO₂, currently rising at 4.7 GtC per year, a NET (negative emission targetting) programme would cost US$10bn per Mg of C ($47bn total). Therefore, the funding secured for the Bonn Challenge ($1bn) is <0.5% of the minimum needed to balance the current growth rate of atmospheric CO₂.

Benefits of tree mixes in afforestation?

Standard aboveground biomass is larger in tree mixes than in averaged monocultures, especially in tree mixtures that include nitrogen fixers; encourages the formation of multiple carbon pools in soils, potentially increasing total carbon storage by up to 30% in highly-degraded landscapes; reduced intraspecific competition for resources; increased resistance to pests and disease.

Mixed forests experience 20% less damage from insect pests due to associational resistance, because insects are confounded in their search for their host’s signal when seeking out a specific tree species when there are diverse tree species present. (Jactel et al, 2020)

Increased species richness in ecosystems increases their resilience to changes in temperature and precipitation, since there is a greater likelihood that at least one species will be versatile to survive in new conditions.

Woodland expansion in the UK - the Western Forest

Woodland expansion is currently not occurring quickly enough to meet legally-binding creation targets by 2050 (16.5% of land cover across the UK). The Western Forest is a project to plant over 20 million new trees, restore 1,400 ha of degraded woodland and create 2,500 ha of new woodland across Western England.

73% of the Western Forest has been designated for agriculture, supporting agroforestry development. This enhances soil quality and crop yields, and increases drought and flood resilience. Planting fruit-bearing trees introduces a long-term income opportunity for farmers.

May boundary future urban development. Pucklechurch Wood is the first 30ha site of the Western Forest, with 22,000 trees planted between 2025-2026, and a further 22,000 projected to be planted in late 2027. This woodland restricts the expansion of the village, which has regional consequences due to Pucklechurch’s close proximity to Bristol.

What are the benefits of protecting other natural terrestrial habitats, not just forests?

Protecting grasslands, wetlands and agricultural lands as well as forests may provide up to 37% of the CO₂ mitigation needed through 2030, increasing the likelihood of reducing global warming to below 2°C by 66%.

What are the benefits of coastal mangrove habitats?

The most carbon-rich ecosystems on the planet, storing 1000 tonnes C/Ha in their biomass and underlying soils. Mangrove decline due to the conversion for aquaculture or coastal development has resulted in a global decline of 8,000km² between 2000 - 2014.

Ecosystem services/natural capital - reduced flood risk to 15 million people, support healthy fisheries, improve water quality, and provide flood protection benefits exceeding US$65bn in property damages each year. (Menedez et al, 2020)

Highlights that restoring and protecting nature should provide co-benefits such as protecting vulnerable ecosystems from floods, droughts, landslides, storms, heatwaves etc. as well as storing emissions.

Particularly beneficial to individuals living in SIDS - nations which produce less than 0.5% of global CO₂ emissions, yet who face extreme vulnerability to climate change and who rely on natural coastal defences like reefs and mangrove habitats (currently on track to lose 75% under RCP 8.5 estimates). Lost ecosystem services in excess of $150bn between 1970-2020 to climate and water-related hazards (IPCC, 2021)

Flood protections from mangroves - Mendenez et al, 2020

Mangroves act as the first line of defence against flooding and erosion; they dissipate up to 66% of wave energy in the first 100m of forest width.

If current mangroves were lost, 29% more land, 28% more people and 9% more property would be damaged per year. The benefits of mangroves increase alongside the severity of the storm; potentially protecting an extra 37 million people and preventing property losses exceeding $270bn during severe 1-in-100-year storm events.

The country which socially and economically benefit the most from mangroves, protecting in excess of $11.31bn of property, is the USA. However, neoliberal deregulation and economic development along the coastline has degraded mangrove forests.

Conversely, the countries which receive the greatest benefit and economic protection from mangroves are developing nations e.g. Belize, Suriname, Mozambique, are also those which have limited ecological footprints. This paradox suggests that the countries worst affected by climate change, sea level rise, and the increased frequency and severity of meteorlogical hazards are also those which have contributed the least to anthropogenic emissions and warming.

Countries with longer mangrove belts, irrespective of the width inland of the mangrove forest, are those which receive the greatest benefits since a greater proportion of the coastline is protected.

Smith et al., 2021 - mangrove restoration in Bangladesh

Coastal communities in Bangladesh affected by cyclones and storm surges which increase erosion and saltwater intrusion planted mangrove species that are more resistant to extreme weather conditions. This reduced wave energy and storm damage, stabilised shorelines, and protected agriculture land and settlements. As well as ecological protection, social and economic co-benefits include enhanced fish stock and crab harvesting, which diversified livelihoods by providing new employment opportunities.

Impacts of greenwashing on tree species diversity in Europe? Yao et al, 2025

Aims to reforest quickly has resulted in many schemes replacing broad-leafed native oak trees with faster-growing conifers, meaning that forest cover on the European continent is 10% greater than it was pre-IR. However, these trees sequester less carbon and they trap heat more efficiently, decreasing local albedo and contributing to global warming by 0.12°C - equivalent to 6% of the warming attributed to burning fossil fuels.

Rewilding in Slovenia case study - Van Hall et al., 2017

Increased soil organic matter content, total nitrogen, bulk density, aggregate stability, and water infiltration (reducing the risk of erosion and overland flow). The benefits of rewilding were primarily found to take effect in the first 5-10yrs of land abandonment, during which period secondary succession takes over for the establishment of small plants, but before the establishment of forests. The high demands of forest cover have decreased environmental benefits due to high water demands, which can cause rivers to run dry during the summer, since this detrimentally impacts settlers who rely on the catchment area.

Blue-green infrastructure in Sweden case study - Sorensen and Emilsson, 2017)

Blue-green infrastructure aims to mimic valuable functions supplied by nature, such as water purification, flood control, water storage and heat control. The implementation of sustainable urban drainage systems through building trenches, ditches, ponds and wetlands in Augustenborg, Sweden (a neighbourhood of Malmo), retains water flows from roofs, roads and car parks. As a result, there have been no floods in the area, compared with five floods between 1994 and 1999. Positive spillover effects include improved provisions of house/business insurance, causing businesses and households to establish themselves in Augustenborg due to improved economic and social stability. Biodiversity has also increased by 50% through the better environment provided to local plants and wildlife.

SuDS (Sustainable Urban Drainage System) - Cambourne, Cambridgeshire (Susdrain, 2011)

In a new-build estate of 35 affordable homes, a range of SuDS components were implemented to demonstrate the wide-scale adoption of practical and innovative water management techniques within new residential developments.

This includes:

• Water butts to collect rainwater

• Permeable paving, allowing water to enter porous storage zones and to filter out pollutants.

• Green sloping roofs to reduce runoff

• Swale channels for excess water, slowing the flow of water and continuing the water treatment process.

• Detention basins to slow the runoff rate and store water on a temporary short-term basis during extreme rainfall events

Benefits include:

• Improvement in the biodiversity, ecology and quality of water in the development

• Cost savings of approximately £11,000 (approx. 10%) due to SuDS. Some financial benefits from grey water collection in water butts, which can be used for watering gardens, cleaning outside etc.

REDD+ scheme in Brazil and tenure rights - afforestation Angelsen, 2009)

REDD - Reducing Emissions from Deforestation and Degradation in developing countries. Proponents of the initiative argue that it can generate large, cheap and quick reductions in global GHG emissions through creating a multilevel system of payments for environmental services. Focuses on Mather, 1992’s forest transition theory, which argues that many developing countries follow a model whereby urbanisation and economic development catalyse deforestation, resulting in forest cover declining in reinforcing loops until agriculture no longer becomes profitable, enabling deforestation rates to fall and the forest to stabilise. REDD+ aims to accelerate forest cover stabilisation or prevent its deterioration in the first instance.

Land tenure is a major preventer of REDD+ initiatives being a suitable NbS. In the Brazilian Amazon there are contested and overlapping claims over land between indigenous populations and the state - with the less powerful stakeholders sidelined in these conflicts due to the economic opportunities in forestry under REDD+. Unclassified public lands account for 24% of the Amazon, and these areas do not qualify for REDD+ payments, which decreases the government’s incentive to afforest or protect forests and makes them vulnerable to extensive logging. Even in communities where there are exclusion rights, they are often not able to exercise them because they lack the government control to prevent invasion from commercial interests. This shows that deforestation can only be inhibited by actions that delimit land tenure and protect marginalised landowners from invasions.

Land grabs from indigenous groups are often orchestrated by Global North-owned organisations who aim to profit - entrenching neo-colonial envrionmental degradation.

Greenwashing - Anderson et al, 2019

The benefits of NbS and the involvement of large, polluting MNCs is increasingly used to distract from the imperative of mitigating emissions from the energy and industrial sectors.

Negative emissions from NbS must be paired with no-delay mitigation for maximum cumulative effect. A swift transition will help to avoid lock-ins associated with the production of new fossil-fuel based products and infrastructure such as cars, factories and power plants, which can extend lifetime emissions for decades.

Nature-based Solutions as discourse - McLennan, 2022

The term ‘Nature-based Solutions’ is a broad and malleable concept - the phrase gained popularity in 2011 following the Fukushima nuclear accident, in relation to disaster risk management rather than to support climate-saving initiatives.

Chevron, 2022, announced an agreement to reforest 9,000 acres of natural cypress forests and swamps n Louisiana as a carbon offsetting tool for their company. Fifteen days later, the same company announced that it plans to spend $67bn developing new oil and gas fields over the next seven years, which blatantly defiles their environmentalist claims. Despite this, the company still assigns responsibility to environmental degradation to a collective “we”, even though they perpetrated many of its dire climatic consequences.

What is adaptation (UNFCCC, 2011)?

Adjustments in ecological, social or economic systems in response to actual or expected climatic stimuli and their effects. It refers to changes in processes, practices and structures to moderate potential damages or to benefit from the opportunities associated with climate change.

What changes may arise as a result of climate change?

Physical systems: rivers, coasts, glaciers, drought

Terrestrial systems: trees, fisheries, biodiversity, wildfire

Marine systems: habitat degradation

Human and managed systems: livelihood, health, food production

Bloschl et al, 2017 - climate change shifting the timing of European floods

River flooding has an estimated annual cost per year of $104bn globally.

Over the past 50 years, warmer temperatures have led to earlier spring snowmelt floods in February through northeastern Europe (Portugal and England; earlier by 13 days per decade), whilst delayed winter storms associated with polar warming - due to changes in NAO, which delayed the arrival of winter storms - have led to later winter floods around the North Sea (southwestern Norway, the Netherlands, Denmark and Scotland; later by 9 days per decade). In western Europe, earlier soil maxima have led to earlier winter floods.

Effects of urbanisation/deforestation in southeastern England may exacerbate the impacts of earlier winter floods. Sustained winter rainfall on saturated soils, which reached their field capacity in earlier months, is made worse through impermeable surfaces which don’t enable rainwater percolation, therefore increasing overland storage and flood run-off. Increasing vegetation coverage may support the infiltration of rainwater, in turn limiting the likelihood of extreme flooding events. Green roofs have the capacity to capture 70% of rainfall over a given time, and sustainable drainage systems can manage rainwater influxes to prevent over

In catchments around the North Sea, delayed winter flooding could lead to softer ground for spring farming operations, which results in higher soil compaction, enhanced erosion and direct crop damage; this has environmental, social and economic implications.

Effects of climate change on disease transmission

Climate change can increase the geographical ranges of vectors such as anopheles mosquitos, which transmit malaria across Sub-Saharan Africa. Other mosquito-borne diseases such as dengue and the West Nile virus may also become endemic in Europe as temperatures, precipitation and humidity increase.

Compared to 1951-1960, by 2013-2022, 10% of the land previously unsuitable for the anopheles mosquito has become a suitable habitat for these vectors to spread malaria, including across Northern Europe, Alaska, Canada, New Zealand and New South Wales.

Negev et al., 2020 - benefits of nature-based city design and urban greening

Urban greening can provide cooling benefits through shade created by tree canopies, and vegetation can intercept solar radiation and therefore reduce ground temperatures. Evapotranspiration releases water vapour into the atmosphere which lowers air temperatures.

Studies in Denmark by Engermann, 2019 determined that children raised in areas with the most restricted access to nature were up to 55% more likely to develop a mental health disorder, even after adjusting for other known risk factors e.g. socio-economic status, urbanisation, and the family history of mental disorders. Other global studies recognise that the benefits of green space are greatest for people from lower socio-economic backgrounds, where income-related health inequalities are more nuanced.

Urban greening can also combat the urban heat island effect, which currently keeps high-density road surfaces, pathways and buildings in urban areas 3-4°C warmer than a surrounding countryside. Cities across Europe could experience summer temperatures up to 10°C higher than the surrounding countryside by 2100 (Pope, 2009). Green roofs result in up to a 75% reduction in demand for cooling and 10% of heating for buildings, reducing electricity demands, via direct shading, evapotranspiration and the conversion of solar radiation to latent heat.

Ecosystem services provided by vegetation acting as porous bodies that absorb airborne pollutants and purify the air are estimated to have removed 2241 tonnes of pollution in London in 2015, valued at £126 million in health benefits.

The Woodlands Trust, 2023 - inequitable distribution of trees

High spatial disparities in urban tree coverage, relative to income. Neighbourhoods with the highest income levels have more than double the tree cover per person than less affluent neighbourhoods. High income neighbourhoods also have 30% less NO₂ and 10% less PM2.5 pollution, associated with significant physical health improvements. The five LAAs in the UK most at-risk from extreme heat - Birmingham, Newham, Tower Hamlets, Hackney and Nottingham - have less than 10% tree coverage.

King and Harrington, 2018 - climate apartheid

Inequitable distribution of local climate change impacts on a global scale. The regions projected to experience the most perceptible climate changes are in the tropics, despite the wealthiest regions of the world (who are the drivers of GHG emissions contributing to climate change) being in the extratropics - inverse relationship between GDP per capita and projected temperature increases. Deemed as ‘climate apartheid’ due to the disparity between how climate change affects differentially impacts social groups.

Exacerbated by climate colonialism - the exploitation of resources of the Global South by Northern nations for their green agendas.

Lemes de Oliveira, 2025 - nature is treated for the instrumental value it provides for humans, ignoring local ontologies/epistemologies.

Although NBS are widely promoted as ways to address climate change, biodiversity loss, flooding, and urban liveability, the concept of “nature” itself is rarely defined. This conceptual ambiguity means that different understandings of nature lead to different planning approaches, values and outcomes.

Anthropocentric worldviews place nature as being a tool to save human problems. Ironic considering the environmental degradation caused by human activity, which has longstanding detrimental impacts on nature. Nature is now understood through a conceptual lens where natural ecological systems have human activity embedded as a part of them. ‘New nature’, including technologically mediated or human-created ecosystems such as aquaponics and engineered woodlands, further stimulate the blur between physical and human-induced ecological processes.

Global Centre on Adaptation, 2024 - community-led NBS in informal settlements

In Barrio 20, an informal settlement located 12km from Buenos Aires’ city centre, intensifying heatwaves are a major climate threat. Exacerbated by the neighbourhood’s lack of green spaces, widespread use of impermeable surfaces, and minimal access to cooling infrastructure. Community-integrated NBS include tree planting, green walls and creating shared communal spaces, which have had both environmental and social benefits for residents. 60% have noted a significant increase in comfort. Possibility to scale-up this project now that it has helped to dispel myths about the cost and complexity of implementing climate solutions to informal settlements.

Oppla, 2021 - Quito’s urban agriculture as a NBS for facing climate change and food insecurity

In Quito, Ecuador, the Agrifood Pact project aims to tackle climate change, poverty and food provision by supporting urban gardens on public and private land, with community participation. Quito’s urban orchards have a production capacity of 1.35 million kgs of food per year, with the majority of this consumed by producers and local families, including in the city’s most vulnerable neighbourhoods where malnutrition rates are high (>30% in infants). Has supported education in schools and for disabled adults, provided matrifocal households the opportunity to earn a wage at home whilst caring for their children, and helped migrants and refugees to be integrated into the society through farming.

In 2013, the northern head of the disused open area of the city’s former airport was designated for urban agriculture activities. This recognises the transferability of the project, enabling it to benefit a wider spatial spread of residents and increase productive capacities.

Woroniecki et al., 2023 - how do NBS strategies help rural communities in the Global South?

A review article from 85 documented nature-based interventions from peer-reviewed studies across Africa, Asia and Latin America.

Determined that 95% of interventions reported reduced vulnerability to climate change, mainly through reduced ecological sensitivity (73%) such as agroforestry for improved soil moisture and fertility, mangroves for reducing coastal erosion, and wetlands for buffering floods.

Reduced social sensitivity through diversified income sources, improved crop yields and enhanced food security (e.g. Quito’s Agrifood Pact, Oppla, 2021) ensures that communities are better able to withstand climate shocks.

Social conditions such as local participation, secure land tenure (link to REDD+ problems, Anglesenn, 2009), equitable benefit sharing and the recognition of Indigenous and local knowledge (link to Lemis de Oliviera, 2025) strongly influence NbS success - without these factors, they may worsen entrenched inequalities.

DEFRA, 2024 - peatland restoration in the UK

Peatland = 1.4mHa across England. 87% is degraded. Under threat due to draining for forestry and farmland, extraction for use as fuel and compost, and burning for grouse moor management. England Government has pledged to restore 32,000 hectares of peat every year - well below CCC progress review suggestions of 67,000ha per year. Scottish government has pledged a further 250,000ha by 2030.

Peat sequesters almost 3.2Gt of carbon, although around 20 million tonnes of greenhouse gases (4% of total UK emissions) are released every year.

Blanket peatlands impede water runoff by up to 10x, slowing the flow of water during storm events to reduce the downstream flood risks. Water-logged peatland also has a lower fuel load because it impedes the above-ground growth of heather, which is susceptible to wildfire burning. By naturally filtering rainwater, peatland restoration also reduces the levels of dirt and sediment washed into rivers, treating it naturally.

1 million pond have been lost in the UK since 1990, reducing biodiversity, yet new pools may be colonised by a diverse assemblage of aquatic organisms.

Glenk et al., 2018 - peat restoration in Scotland benefits

Carbon capture, habitat provisions and regulation of water quality from restored peatlands provide ecosystem services. Restoring 20% of Scottish peatlands would result in an economic benefit of between £80 - £290 million over a period of 15 years. Delaying the restoration of peatland until 2040 could result in a £100 million reduction of economic benefits to society.