David Rogers, Boram Lee, Vladimir Tsirkunov, Alan Thorpe, Makoto Suwa, Anna-Maria Bogdanova and Brenden Longman |  June 2022

Find the panel discussion on this subject in the GFDRR/GWEF new economy series. 
 

Climate projections for NbS

For many NbS, reliable information is needed on changes in precipitation, temperature, and extreme meteorological and hydrological hazards. Yet, obtaining credible projections of climate change at local scales has been, and remains, challenging. The limited understanding and high level of uncertain of future climate projections and how systems will respond to long-term effects of climate variability could limit the effectiveness of NbS approaches. Rizvi and van Riel (2014) collated the following knowledge gaps:

• Projections of climate change impacts and access to meteorological data at local scale
• Sector specific information on projected impacts of climate change
• Relationship between climate, hydro-geological changes and water induced hazards
• Combined impact of climate change and economic development on specific sectors
• Other drivers of change, such as deforestation, invasive species, human population growth impact on the ability of ecosystems underpinning NbS to deliver sustainable adaptation services
• Socio-economic aspects of climate change impacts related to water resources
• Potential impacts of climate change on existing and future water development infrastructures
• Environmental vulnerabilities due to natural hazards affect ecosystems and natural resources

More recently, advances in numerical modelling have offered significant capabilities to attribute the potential for NbS to moderate the impact of climate change. Holden et al. (2022), for example, used a multi-model approach linking climate and hydrological model simulations to attribute climate change ecosystem modification to drought-period stream flow. The method utilized a 68-member ensemble from the Hadley Centre regional model (HadRM3p) nested in the Hadley Centre Global Model (HadAM3P-N96), a 50-member ensemble from ECHAM5.4 and a 27-member multi-model ensemble from CMIP5. These simulations were used as input to a local validated, physically based hydrological model (MIKE SHE) coupled with a channel routing model (MIKE HYDRO). The authors were able to represent each climate state by 145 hydrological model simulations, which were applied to determine the impact of invasive trees on stream flow, modelling the current, cleared, and invaded state of the ecosystem. Their results highlight the potential for NbS for drought and flood mitigation as well as the importance of access to reliable climate projections and analyses. The ability to downscale through nesting models is critical to create information at the appropriate scales for intervention.

Assessment of NbS

There are relatively few quantitative assessments of the impact of NbS, particularly in developing countries. Examples include studies on the value of coastal wetlands for flood reduction (Narayan et al. 2017); the value of coral reefs for flood risk reduction (Reguero et al. 2021); the value of NbS for urban flood management (Wishart et al. 2021); and green space influence on urban heat island mitigation (Park et al. 2017).

As the ability to attribute past meteorological and hydrological extremes to climate change improves, so does the opportunity to assess the potential of NbS interventions. For example, attribution studies have focused on physical climate variables associated with specific extremes such as rainfall, temperature, or relevant indices that use these variables. A few studies have gone further to assess the propagation of human influence on climate extremes through to an attributable impact on hydrological systems or society (Holden et al. 2022).

At the same time, knowledge of the future climate at local scales is essential to make the right interventions. Afforestation actions have been taken places in many places in the effort of atmospheric carbon sequestration, by replacing native grasslands to non-native trees. While trees may be useful in absorbing large amounts of water and reduce flood risk, the reduced stream flow would increase drought risk if low rainfall conditions prevail. And the benefit of increased atmospheric carbon sequestration is yet to be quantified in consideration of the the natural capacity of carbon capture by native grasslands. Comprehensive understanding and application of weather/water/climate projection, and their integration with ecosystem modelling, is critical for the assessment of the impact of such interventions.

Both spatial and temporal dimensions are essential in evaluating NbS. For example, the effect of greenspace on environmental quality will differ as a consequence of changing weather (e.g. level of direct sunlight) and atmospheric circulation patterns (Hutchins et al. 2021). The benefit of implemented NbS to mitigate air pollution may be quantified differently, depending on the scale, domain, and the inclusion of long-range transportation and deposition modelling of target pollutants.

Level and type of engineering/innovation of nature versus delivery of ecosystem services and number of ecosystem services and stakeholder groups. NBS can range from more natural solutions including managed ecosystems to highly engineered novel ecosystems (Lechner et al. 2020 after Eggermont et al. 2015)

NbS in developing economies

The shift from conventional engineering solutions to adapt to climate change is gaining momentum within developed economies at a much faster pace than in developing ones (cf., Lechner et al. 2020). NbS can be a more cost-effective and sustainable approach to address societal challenges from climate change and urbanization. They have the potential to provide energy and resource efficient responses to climate change, can build natural capital, and enhance the green economy.

The World Bank is scaling up NbS to address climate challenges to help developing countries build resilience. There are significant opportunities but also impediments where traditional engineering solutions are seen as tangible interventions relative to nature-based ones. Engaging local communities is also challenging where NbS require changes in community livelihood practices. NbS require direct local community and individual ownership to sustain the managed ecosystem and this needs to be tied to direct, measurable benefits and co-benefits to these communities. Creating opportunities for local communities to develop and manage the implementation of their own projects supported by development partners and governments is a way to integrate rural households, for example, into wider sustainable value chains in districts and beyond.

For further discussion on this subject, find the GFDRR/GWEF new economy series.

References

Holden P B, Rebelo A J, Wolski P, Odoulami R C , Lawal K A, Kimutai J, Nkemelang T and New M G (2022) Nature-based solutions in mountain catchments reduce impact of anthropogenic climate change on drought streamflow. Commun. Earth Environ. 3, 51. https://doi.org/10.1038/s43247-022-00379-9

Hutchins M G, Fletcher D, Hagen-Zanker A, Jia H, Jones L, Li H, Loiselle S, Miller J, Reis S, Seifert-Dähnn I, Wilde V, Xu C-Y, Yang D, Yu J and Yu S (2021). Why scale is vital to plan optimal Nature-Based Solutions for resilient cities. Environ. Res. Lett. 16 044008

Lechner A M, Rachel L G, Rodrigues L, Ashfold M J, Selvam S B, Wong E P, Raymond C M, Zieritz A, Sing K W, Billa P M L, Sagala S, Cheshmehzangi A, Lourdes K, Azhar B, Sanusi R, Ives C D, Tang Y T, Tan D T, Chan F K S, Nath T K, Sabarudin N A B, Metcalfe S E, Gulsrud N M, Schuerch M, Campos-Arceiz A, Macklin M G and Gibbins C (2020) Challenges and considerations of applying nature-based solutions in low- and middle-income countries in Southeast and East Asia. Blue-Green Systems 1; 2 (1): 331–351. doi: https://doi.org/10.2166/bgs.2020.014

Narayan S, Beck M W, Wilson P, Thomas C J, Guerrero A, Shepard C C, Reguero B G, Franco G, Ingram J C and Trespalacois D (2017). The Value of Coastal Wetlands for Flood Damage Reduction in the Northeastern USA. Sci. Rep. 7, 9463.

Park J, Kim J H, Lee D K, Park C Y and Jeong S G (2017) The influence of small green space type and structure at the street level on urban heat island mitigation. Urban forestry & urban greening, 21, 203-212.

Reguero B G, Storlazzi C D, Gibbs A E, Shope J B, Cole A D, Cumming K A and Beck M W (2021) The value of US coral reefs for flood risk reduction. Nature Sustainability, 1-11.

Rizvi A and van Riel K (2014) Nature Based Solutions for Climate Change Adaption – Knowledge Gaps. An Analysis of Critical Knowledge Gaps, Needs, Barriers and Research Priorities for Adaptation. IUCN 2014.

Wishart M, Wong, T, Furmage B, Liao X, Pannell D and Wang J (2021) The Gray, Green, Blue Continuum : Valuing the Benefit of Nature-Based Solutions for Integrated Urban Flood Management in China. World Bank, Washington, DC. https://openknowledge.worldbank.org/handle/10986/35687 License: CC BY 3.0 IGO

The Global Program on Nature-Based Solutions (NBS) for Climate Resilience, World Bank / GFDRR: https://naturebasedsolutions.org/