While the term “nature-based solutions” may have been coined relatively recently, communities worked with nature’s strengths to enhance societal resilience long before modern civilisation. For example, the Aztecs developed an agro‐hydrological system, known as the Chinampas, to build resilience against drought. They created rectangular areas of fertile arable land by dredging mud and creating canals. Not only did this technique replenish the nutrients in the soil for the crops, it also created a habitat for fish and birds, which in turn helped maintain the health of the ecosystem as well as provided additional sources of food. The drainage systems also mitigated flooding during the rainy season.
Today, over-exploitation of natural resources and intensive land-use is causing environmental degradation and an unprecedented rate of species extinction. Climate change will only accelerate these processes and add new challenges. Nature-based solutions (NbS) are attracting increasing attention as a way to address these inter-related issues.
Solutions grounded in nature offer an impressive array of benefits
If you look at water-related climate risks, for example, NbS provide many co-benefits:
- Wetlands reduce flood risk by enhancing water absorption, while contributing to better water quality and enhancing biodiversity. In the United States, it is estimated that coastal wetlands provide USD 23.2 billion in storm protection services annually. However, over 85% of global wetlands have been lost over the past three centuries.
- Mangroves provide critical protection against coastal risks, acting as a speed bump to attenuate the impact of storm surge, while protecting habitats. At the same time, their carbon sequestration potential is significant. Without mangroves, an estimated 15 million more people worldwide would suffer from coastal flooding each year. However, mangroves cover around the world has decreased by 20 to 35% since the 1980s.
- Forests decrease land erosion and increase slope stability, while helping to absorb carbon emissions from the atmosphere, improving air quality and protecting the habitats of many species. In Switzerland, the benefits of protected forests have been estimated at USD 2-3.5 billion per year due to avoided costs of avalanches, landslides and flooding. Yet, deforestation and forest degradation worldwide continue at alarming rates.
- Green spaces in cities can reduce the urban heat island effect while mitigating flood risk by reducing runoff and increasing absorption capacity, as well as contributing to improved air quality by trapping or absorbing air pollutants emitted by power plants, factories and vehicles. For example, the installation of green roofs is mandatory in Toronto and Copenhagen for certain new constructions.
The potential of NbS remains underexploited despite many examples of good-practice
While many countries have started to recognise the importance of NbS in their national climate adaptation and mitigation policies, their potential remains under-exploited. In recent work at the OECD, we highlighted some of the challenges that practitioners face in increasing the use of NbS for addressing water-related climate risks. In addition to lack of awareness and of technical capacity, two major obstacles prevail:
- Grey dominates green: the policy and regulatory environment for measures that reduce climate related water risks, for example, strongly favours the use of grey solutions, such as levees and dams. This is reinforced by a misguided perception that NbS only yield (uncertain) benefits in the long-term, while engineered solutions are immediately effective and well understood.
- Quantifying and capturing benefits to secure funding: There are inherent difficulties in quantifying many of the benefits NbS offer such as species protection, air or water quality improvement, and so on. In addition, the dispersion of values created across stakeholders contributes to the difficulty to capture NbS values for financiers. The lack of quantification of benefits and the lack of robust performance data make it hard for NbS to compete against established engineering measures.
Countries are working to overcome these barriers
From our ongoing country-focused analysis, we find reason for why this might change in the future.
Countries have begun to incentivise the use of NbS: for example, in Norway, central government planning guidelines encourage municipalities and counties to consider the conservation, restoration or use of NbS in their planning processes and require authorities to provide justification if other engineered methods are chosen. The UK’s National Planning Policy Framework similarly recommends local authorities to consider the use of natural flood management in new property or infrastructure development projects when appropriate. These efforts reflect the international political momentum given to NbS.
Established funding mechanisms are being adapted to include NbS: for example, NbS became eligible for funding under Canada’s CAD 1.6 billion Disaster Mitigation and Adaptation Fund and the UK’s Flood and Coastal Resilience Innovation Programme. International funding has also been an accelerator for NbS. For example in Mexico, the Global Environmental Facility (GEF) supports a number of larger scale NbS projects, such as mangrove restoration and riparian reforestation, coral reef protection and water flow rehabilitation, intended to reduce the risk of climate-related disasters in the Gulf of Mexico.
Technical capacities for NbS are being reinforced: the skills and knowledge needed to implement NbS may differ from those needed for grey solutions (e.g. understanding of biodiversity impacts). In recognition of this, Mexico has started to include NbS in tertiary education curricula, as is the case with the Universidad Nacional Autónoma de México (UNAM).
Developments in 2021 give cause for some optimism in relation to NbS. Countries and organisations are gearing up their pledges to support NbS for climate change adaptation at the Climate Adaptation Summit to take place on 25-26 January. Similarly, the UNFCCC COP26 later this year will promote nature as a key solution to tackling climate change.
Further reading
- For more information on OECD work on climate adaptation, visit: http://www.oecd.org/environment/cc/climate-adaptation/
- OECD (2020), “Nature-based solutions for adapting to water-related climate risks“, OECD Environment Policy Papers, No. 21, OECD Publishing, Paris.
- 2021: Adaptation comes to the fore, OECD Environment Focus Blog
