Nature-based Solutions for Climate Adaptation

Key Findings from IPCC AR6 WGII 2022 Report and World Economic Forum Global Commission on BiodiverCities

by Dr. Timon McPhearson, IPCC Lead Author, WG II

The historic report released by the Intergovernmental Panel on Climate Change (IPCC) released in February 2022 explores the challenges and potential for leveraging nature-based solutions to advance climate adaption globally. This brief summary discusses some of the key takeaways and recommendations from IPCC contributors and authors from across the world.

How Nature-based Solutions (NbS) is framed in IPCC

Nature-based Solutions (NbS) are “actions to protect, sustainably manage, and restore natural or modified ecosystems, that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits(IUCN, 2016).

Major reports have highlighted the role of NbS for climate adaptation, mitigation, and biodiversity protection including:

Take Home Message

Nature-based Solutions are:

  • Cost effective
  • Scalable
  • Durable
  • Viable
  • Offer immediate climate solutions

Yet, NbS are not silver bullets and significant challenges and knowledge gaps limit wider implementation.


1. Ecosystem-based Adaptation (EbA; or NBS) can deliver climate change adaptation for people with multiple additional benefits, including for biodiversity.

  • Climatic risks to people, including from flood, drought, fire and over-heating, can be lowered by a range of EbA in urban and rural areas. However, EbA and other NbS are still not widely implemented.
  • Public parks, urban forests, street trees and green roofs as well as lakes, ponds and streams are widely documented for providing local cooling, grass and riparian buffers and forested watersheds can enhance flood and drought protection for cities and settlements, and mangrove stands and wetlands in coastal areas can reduce storm surges.

2. NBS can be more flexible and cost effective for providing flood risk reduction, heat risk reduction, and other benefits than other adaptation options. A widely adopted model in New York City found that green infrastructure costs were half that of grey infrastructure costs for improving urban stormwater absorption.

  • Analysis of the impacts of Hurricane Sandy showed that communities located behind wetlands experienced 20% less damage.
  • Coral reefs are providing $544M per year and mangroves $22USDB in property protection for coastal communities in the US and Mexico.
  • NbS are not only generally less expensive but strengthen over time, compared with built infrastructure which erodes with time
  • By 2030, flooding from changes in storms, sea level rise (based on RCP8.5) and increases in built infrastructure in the US Gulf Coast may result in net economic losses of up to US$176 billion, of which US$50 billion could be avoided through implementation of nature-based measures including wetland and oyster reef restoration and other green infrastructure (EPA, 2015b; Reguero et al., 2018).

4. Natural ecosystems can provide carbon storage and sequestration at the same time as providing multiple other ecosystem services, including EbA.

  • EbA forms part of a wider range Nature-based Solutions (NbS) actions and some have mitigation co-benefits, including the protection and restoration of forests and other high-carbon ecosystems, as well as agroecological farming practices.
  • Development and climate mitigation co-benefits of NBS (including for public health) is an additional reason that NBS are being increasingly taken up by cities including for improving health and livelihoods, particularly for poor, marginalized groups

6. Potential for EbA is large if finance for NBS can be motivated. Globally 90% of climate finance is for mitigation.

7. A range of analyses have concluded that ~30% of Earth’s surface needs to be effectively conserved to maintain biodiversity and ecosystem services.

  • US protected land area is 12% but is 10% of global total protected area, underlining US opportunity for leadership, and global challenge to meet biodiversity conservation targets

8. Adaptation strategies that treat climate, biodiversity and human society as coupled systems will be most effective.

9. NbS are, on average, 50% more cost-effective than “grey” alternatives and deliver 28% more added value, yet they received just 0.3% of overall spending on urban infrastructure in 2021. (WEF 2022)

10. Globally, expanding nature in the built environment creates significant economic and social value. Spending $583 billion on NbS for infrastructure and on interventions that release land to nature could create more than 59 million jobs by 2030, including 21 million livelihood- enhancing jobs dedicated to restoring and protecting natural ecosystems. (WEF 2022)


1. Unintended consequences of investing in green infrastructure for NBS can contribute to gentrification, displacement, create more public use, increase water demand

2. Studies demonstrating efficacy in multiple social and ecological contexts are still needed. Most studies rely on modeled scenarios and field data remains thin. Evaluating the efficacy of NbS may become more tractable with more uniform guidelines for implementation, and coordination in scaling-up local-level NbS measures is likely to facilitate long-term success.

3. Post implementation evaluation is needed to improved understanding of cost effectiveness for disaster risk reduction and deliver critical co-benefits for human well-being.

4. Despite increasing knowledge about NBS recent studies indicate that nature-based approaches to adaptation and resilience are still under-recognised and under-invested in urban planning and development despite the potential scale of benefits

a. for example, a recent study covering 70 cities in Latin America calculated that 96 million people would benefit from improving main watersheds with green infrastructure)

5. To realize potential benefits and avoid harm, it is essential that EbA is deployed in the right places and with the right approaches for that area, with inclusive governance (Ch2)

a. Interdisciplinary scientific information and practical expertise, including local and Indigenous knowledge, are essential to effectiveness (high confidence). There is a large risk of maladaptation where this does not happen (high confidence).

6. Need for Coproduction: Effective NbS requires a well-coordinated suite of adaptation efforts (e.g., assessment, planning, funding, implementation, and evaluation) that is co-produced among stakeholders and across sectors

7. Ecosystem restoration and resilience building cannot prevent all impacts of climate change, and adaptation planning needs to manage inevitable changes to species distributions, ecosystem structure and processes (Ch.2) Ecosystem-based Adaptation and other Nature-based Solutions are themselves vulnerable to climate change impacts.

8. Extreme events are compressing the timeline available for natural systems to adapt and impeding our ability to identify, develop and implement solutions.

Dr. Timon McPhearson is the Director of the Urban Systems Lab and professor of Urban Ecology at The New School. In 2018 he was appointed as a member of the Intergovernmental Panel on Climate Change (IPCC) and lead author for the urban chapter. He is also a Research Fellow at the Cary Institute of Ecosystem Studies in Millbrook, New York, and at the Stockholm Resilience Center at Stockholm University in Sweden.

Follow him on ResearchGate, Google Scholar, and LinkedIn.

Citation: Dodman, D., B. Hayward, M. Pelling, V. Castan Broto, W. Chow, E. Chu, R. Dawson, L. Khirfan, T. McPhearson, A. Prakash, Y. Zheng, and G. Ziervogel. (2022). Cities, Settlements and Key Infrastructure. In: Climate Change 2022: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press.



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