Assessing the long-term effectiveness of Nature-Based Solutions under different climate change scenarios

A quantitative review of nature-based solutions for urban sustainability (2016-2022): From science to implementation

Nature-based solutions (NBS) have great potential for achieving urban sustainability. While several reviews have comprehensively examined NBS, few have focused on its role in addressing urban sustainability challenges. Here we present a systematic review of 142 case studies selected from English papers published in SCI journals (i.e., indexed by Web of Science) during 2016-2022, whose titles, abstracts or keywords contain both urban-related terms and NBS-related terms. Using multiple methods, including statistical analysis, deductive content analysis, and inductive content analysis, we found that: (1) NBS have primarily been utilized to address urban flooding (43 %) and heat stress (21 %), with green roofs (24 %) and urban forests (16 %) being the most extensively studied NBS for tackling these challenges. (2) The ecosystem services (ES) capacity of NBS has been heavily researched (57 %), while studies addressing ES flows (7 %) and ES demand (18 %) are limited. (3) Most studies involved at least one NBS implementation process (83 %), but primarily focused on selecting and assessing NBS and related actions (66 %), with fewer studies on designing and implementing NBS and transferring & upscale NBS. We suggest that future research should contribute to the establishment of a checklist to assist in identifying which NBS types are effective in addressing specific urban sustainability challenges in varying contexts. Integrating the science and practice of NBS for urban sustainability is also crucial for advancing this field.

The underexposed nature-based solutions: A critical state-of-art review on drought mitigation

Droughts are the most expensive climate disasters as they leave long-term and chronic impacts on the ecosystem, agriculture, and human society. The intensity, frequency, and duration of drought events have increased over the years and are expected to worsen in the future on a regional and planetary/global scale. Nature-based solutions (NBS) such as wetland and floodplain restorations, green infrastructures, rainwater harvesting, etc., are highlighted as effective solutions to cope with the future impacts of these events. While the role of NBS in coping with the impacts of other disasters, such as floods, has been extensively studied, there has been a lack of comprehensive review of NBS targeting drought. The following paper provides a unique critical state-of-the-art literature review of individual drought-related NBS around the world, in Europe, and particularly in Belgium, and assesses the critical differences between the NBS applied globally and in Flanders. An extensive literature review was conducted to systematically analyze NBS, listing the type, the location, the status of the implementation, and the possible recommendations proposed to optimize future NBS applications. Finally, a comparison is made between small- and large-scale applications of NBS. By analyzing all these aspects, especially the level of effectiveness and recommendations, insight was gained into the future potential of NBS and possible improvements. The research indicated a lack of scientific publications, especially in Belgium. Hence, grey literature was also included in the literature review. Only four papers included a quantitative assessment regarding the effectiveness of drought on a global level, all stating a positive impact on groundwater recharge. In contrast, at regional and country levels, the performance of NBS was not quantified. The number of large-scale implementations is low, where landscape- or watershed-scale holistic approaches to drought mitigation are still scarce. Some successfully implemented projects are only very local and have a long realization time, two aspects that limit achieving visible impact at a larger scale. Among the many NBS, wetlands are recognized as highly effective in coping with drought but are still degraded or lost despite their significant restoration potential. A common effectiveness evaluation framework shall be followed, which gives policymakers a clear view of the different NBS investment options. Furthermore, a more collaborative approach is recommended globally, including different stakeholder groups, with specific attention to the local communities. To conclude, future research should increase the evidence base and implementation of drought-mitigating NBS.

Review of Nature-based Solutions in Dryland Ecosystems: the Aral Sea Case Study

NbS have gained substantial attention in the academic literature recently as a potential approach for simultaneously tackling environmental issues and addressing societal challenges. Drylands, which are among the world's most vulnerable areas to the impacts of climate change and cover a little less than the half of the global terrestrial surface, were the focus of this study. We conducted a systematic literature review to explore the potential opportunities for the application of NbS in rural drylands across the globe. We go on to specifically consider the possibility of applying selected NbS approaches in the Aral Sea region of Uzbekistan, as a case study of a dryland ecosystem illustrating major environmental and social challenges. We highlight which NbS show the most promise in the Aral Sea region and conclude with a discussion of existing gaps in the literature on NbS in drylands, and opportunities for further research.

Analysis of potential nature-based solutions for the Mun River Basin, Thailand

Despite the growth in research and applications of nature-based solutions (NBS) within the literature, there are limited applications in South East Asia, moreover studies which quantitatively assess the impacts of NBS could have on hazard reduction are scarce. This paper addresses this gap by developing and validating MCDA-GIS analysis to map how potential nature strategies could mitigate flood hazard if applied within the Mun River Basin, Thailand. Through a literature review, the top three solutions for flood and drought hazards were found: wetlands, re/afforestation, and changing crop types. These strategies were reviewed and validated with a MCDA-GIS methodology, through land use change (LUC) maps to depict different future scenarios. The results found that flood hazard did decrease when NBS were implemented in the catchment, especially for A/Reforestation, and to a greater extent when a combination of NBS were applied. This article provides specific insights into the current gaps of NBS publications, specifically considering the case of the Mun River Basin, Thailand.

A Digital Twin modelling framework for the assessment of seagrass Nature Based Solutions against storm surges

In this paper we demonstrate a novel framework for assessing nature-based solutions (NBSs) in coastal zones using a new suite of numerical models that provide a virtual "replica" of the natural environment. We design experiments that use a Digital Twin strategy to establish the wave, sea level and current attenuation due to seagrass NBSs. This Digital Twin modelling framework allows us to answer "what if" scenario questions such as: (i) are indigenous seagrass meadows able to reduce the energy of storm surges, and if so how? (ii) what are the best seagrass types and their landscaping for optimal wave and current attenuation? An important result of the study is to show that the landscaping of seagrasses is an important design choice and that seagrass does not directly attenuate the sea level but the current amplitudes. This framework reveals the link between seagrass NBS and the components of the disruptive potential of storm surges (waves and sea level) and opens up new avenues for future studies.

Simulation of Vegetation Carbon Sink of Arbor Forest and Carbon Mitigation of Forestry Bioenergy in China

Mitigating carbon emissions through forest carbon sinks is one of the nature-based solutions to global warming. Forest ecosystems play a role as a carbon sink and an important source of bioenergy. China's forest ecosystems have significantly contributed to mitigating carbon emissions. However, there are relatively limited quantitative studies on the carbon mitigation effects of forestry bioenergy in China, so this paper simulated the carbon sequestration of Chinese arbor forest vegetation from 2018 to 2060 based on the CO2FIX model and accounted for the carbon emission reduction brought about by substituting forestry bioenergy for fossil energy, which is important for the formulation of policies to tackle climate change in the Chinese forestry sector. The simulation results showed that the carbon storage of all arbor forest vegetation in China increased year by year from 2018 to 2060, and, overall, it behaved as a carbon sink, with the annual carbon sink fluctuating in the region of 250 MtC/a. For commercial forests that already existed in 2018, the emission reduction effected by substituting forestry bioenergy for fossil energy was significant. The average annual carbon reduction in terms of bioenergy by using traditional and improved stoves reached 36.1 and 69.3 MtC/a, respectively. Overall, for China's existing arbor forests, especially commercial forests, forestry bioenergy should be utilized more efficiently to further exploit its emission reduction potential. For future newly planted forests in China, new afforestation should focus on ecological public welfare forests, which are more beneficial as carbon sinks.