Nature-based Solutions Research Articles

Nature-based solution enhances resilience to flooding and catalyzes multi-benefits in coastal cities in the Global South

Coastal cities are facing a rise in groundwater levels induced by sea level rise, further triggering saturation excess flooding where groundwater levels reach the topographic surface or reduce the storage capacity of the soil, thus stressing the existing infrastructure. Lowering groundwater levels is a priority for sustaining the long-term livelihood of coastal cities. In the absence of studies assessing the possibility of using tree-planting as a measure of alleviating saturation excess flooding in the context of rising groundwater levels, the multi-benefit nature of tree-planting programs as sustainable Nature-based solutions (NBSs) in coastal cities in the Global South is discussed. In environments where groundwater is shallow, trees uptake groundwater or reduce groundwater recharge, thereby contributing to lower groundwater levels and increasing the unsaturated zone thickness, further reducing the risk of saturation excess flooding. Tree-planting programs represent long-term solutions sustained by environmental factors that are complementary to conventional engineering solutions. The multi-benefit nature of such NBSs and the expected positive environmental, economic, and social outcomes make them particularly promising. Wide social acceptance was identified as crucial for the long-term success of any tree-planting program, as the social factor plays a major role in addressing most weaknesses and threats of the solution. In the case of Nouakchott City (Mauritania), where a rise in groundwater levels has led to permanent saturation excess flooding, a tree-planting program has the potential to lower the groundwater levels, thereby reducing flooding during the rainy season.

Phytoremediation of pharmaceuticals and personal care products using the constructed wetland

Pharmaceuticals and personal care products (PPCPs) are ubiquitously found pseudo-persistent group of emerging contaminants that causes ecotoxicity even at nano-concentrations. Due to their persistence and bio-accumulative behavior, long-term exposure to these pollutants increases the risk of severe health disorders in humans and poses ecological risks to aquatic life. Sedimentation, membrane filtration, advanced oxidation, activated sludge, and membrane bioreactors are a few of the treatment processes with treatment efficiency ranging from 50 to 95%, but they have limitations such as high investment, towering operating costs, use of chemicals, membrane fouling issues etc. Constructed wetlands (CW) are promising low cost, nature-based solutions having potential of PPCPs removal by simultaneous action of physical, chemical and biological processes. Herein, substrate material, plants and microbes play crucial roles in eliminating PPCPs. Phytoremediation of PPCPs occurs via plant uptake, translocation and degradation. Plants like Canna indica and Phragmites australis have shown ~70–90% antibiotics removal efficiency. Biofilm formation and colonization of microbes lead to the microbial degradation of micro-pollutants apart from the synergistic effect of the plant-endophytic relationship. This bacterial property could be used in CWs for bioremediation of water and wastewaters, as substrates provide substratum for microbial adherence and biofilm formation. Quorum sensing (QS) is a density-based cell-communication system where bacterial cells send signals among themselves during biofilm formation. In this respect, QS-assisted biodegradation via augmentation of engineered bacteria with genes to enhance QS can be a novel approach for the degradation of organic pollutants in CWs with microbial richness.

Glaring gaps in tools to estimate businesses’ biodiversity impacts hinder alignment with the Kunming-Montreal global biodiversity framework

The Kunming-Montreal Global Biodiversity Framework, in a first-time move, calls for companies and financial institutions to measure and report their impacts on biodiversity. While many tools that measure businesses' biodiversity footprints have recently emerged (“biodiversity indices”), it is unclear whether they really allow companies to measure what the Global Biodiversity Framework requires. Identifying gaps in biodiversity indices concerning the GBF would aid businesses and strengthen its implementation. To fill this gap, here we assessed the degree of the alignment between the indices and the Global Biodiversity Framework. The businesses’ biodiversity indices identified by the European Union Business @ Biodiversity Platform and the Taskforce for Nature Financial Disclosures were selected. A semi-quantitative gap analysis was applied to compare their capabilities against the metrics extracted from the Global Biodiversity Framework. The glaring gaps were found in existing biodiversity indices in the coverage of the metrics needed to support the implementation of the Global Biodiversity Framework by businesses. Metrics related to ecosystem integrity, connectivity and restoration, nature-based solutions, sea use change, aquatic biodiversity, genetic diversity and resources, the territory and knowledge by Indigenous Peoples, and urban green and blue spaces were insufficiently addressed by most available biodiversity indices. There is an urgent need to develop integrated biodiversity indices if businesses are to effectively measure and disclose their impacts on biodiversity in a way more consistent with the Global Biodiversity Framework.

Incorporating suburban cropland into urban green infrastructure: A perspective of nature-based solutions in China

Urban green infrastructure (GI) addresses human social development issues and challenges through urban green space ecosystem services. However, the ecosystem service functions of suburban cropland, especially regulating services and cultural services, have been seriously underestimated. The distribution of green spaces and suburban cropland varies in different regions of China, as well as their potential development methods. This article examines the potential of integrating suburban cropland into urban green infrastructure, offering a perspective on nature-based solutions in China. We divided the suburban cropland in China into three parts: peri‑suburban, mid-suburban, and outer-suburban by the concept of 15-minute living circle based on different travel modes of people. Based on statistical yearbook data, satellite remote sensing images and the fragstats 4.2 programme, a quantitative analysis was conducted on the spatial distribution, landscape pattern and social development of suburban farmland and green space in four cities. Then, the potential for improving the exposure level of suburban cropland after incorporating suburban cropland into urban green infrastructure was quantified and compared. Finally, we explored the potential development of the three kinds of suburban cropland as green infrastructure based on the concept of NbS. We found the spatial pattern of cropland and green space in the mid-suburban is greatly affected by regional geographical conditions, the green exposure level, i.e., green space availability indicators, in Beijing, Shanghai, Guangzhou, and Xi'an increased by 83 %, 300 %, 24 %, and 612 %, respectively, after incorporating suburban cropland into urban green infrastructure. The potential development models for suburban cropland should be based on NbS and China's national conditions: peri‑suburban cropland should be fully utilized for cultural and social functions, the mid-suburban cropland should focus on multifunctional utilization of cropland, and the outer-suburban is prioritized for ecological functions. Our study provides scientific insights for deep exploration of the functions of suburban cropland in China.

What-if nature-based storm buffers on mitigating coastal erosion

Creating ecosystem buffers in intertidal zones, such as seagrass meadows, has gained increasing attention as a nature-based solution for mitigating storm-driven coastal erosion. This study presents what-if scenarios using an integrated model framework to determine the effectiveness and strategies for planting seagrass to reduce coastal erosion. The framework comprises two levels of simulation packages. The first level is a regional-scale coupled hydrodynamic model that simulates the processes of a specific storm and provides boundary forces for the morphodynamic model XBeach to apply at the next level, which simulates nearshore morphological evolution. The framework is applied to the open coast of Norderney in the German Bight of the North Sea. We demonstrate that optimising the location and size of seagrass meadows is crucial to increase the efficiency of onshore sediment erosion mitigation. For a specific depth range, depending on the storm's intensity, the most significant reduction in erosion may not be achieved by starting the meadow at the depth that permits the largest meadow size. To maintain a significant coastal protection effect, seagrass density and stem height should be considered together, ensuring erosion reduction by at least 80 % compared to the unprotected coast. This study provides valuable insights for the design and implementation of seagrass transplantation as a nature-based solution, highlighting the importance of considering location, size, density, and stem height when using seagrass meadows for coastal protection.

Ecological impact of pharmaceutical pollutants and options of river health improvements - A risk analysis-based approach

Pharmaceuticals are one of the emerging pollutants (EPs) in river waters across the world. Due to their toxic effects on aquatic organisms, they have drawn the global attention of the scientific community concerned with river ecosystems. This paper reviews the existing occurrence data for various pharmaceutical pollutants (PPs) reported in river waters in some part of the world and their ecological impacts. Using algae, macroinvertebrates (MI), and fish as biotic indicator groups in water to reflect river health conditions, an attempt has been made to assess the ecological risk due to the presence of PPs in the water environment.After ascertaining the predicted no-effect concentration (PNEC) of PPs for selected groups of aquatic organisms, the risk quotient (RQ) is estimated based on their measured environmental concentration (MEC). When MEC > PNEC and RQ > 1 for any of the biotic indicator, ecologically it is ‘high risk’ condition. The determination of PNEC uses a minimum assessment factor (AF) of 10 due to uncertainty in data over the no observed effect level (NOEL) or lowest observed effect level (LOEL). Accordingly, MEC 10 times higher than PNEC, (RQ = 10) represents a threshold risk concentration (RCT) beyond which adverse effects may start showing observable manifestations. In the present study, a new classification system of ‘high risk’ conditions for RQ = 1–10 has been proposed, starting from ‘moderately high’ to ‘severely high’. For RQ > 10, the ecological condition of the river is considered ‘impaired’.For river health assessment, in the present study, the whole range of physico-chemical characteristics of river water quality has been divided into three groups based on their ease of measurement and frequency of monitoring. Dissolved oxygen related parameters (DORPs), nutrients (NTs), and EPs. PPs represent EPs in this study. A framework for calculating separate indicator group score (IGS) and the overall river health index (RHI) has been developed to predict indicator group condition (IGC) and river health condition (RHC), respectively. Color-coded hexagonal pictorial forms representing IGC and RHC provide a direct visible perception of the existing aquatic environment and a scientific basis for prioritization of corrective measures in terms of treatment technology selection for river health improvements.The analyses indicate that many rivers across the world are under ‘high risk’ conditions due to PPs having MEC > PNEC and RQ > 1. Up to RCT, (where RQ = 10), the ‘high risk’ condition varies from ‘moderately high’ to ‘severely high’. In many instances, RQ is found much more higher than 10, indicating that the ecological condition of river may be considered as ‘impaired’. Algae is the most frequently affected group of biotic indicators, followed by MI and fish.A review of treatment methods for selection of appropriate technology to reduce the pollution load, especially PPs from the wastewater streams has been summarized. It appears that constructed wetlands (CWs) are at present the most suitable nature-based solutions, particularly for the developing economies of the world, to reduce the concentrations of PPs within limits to minimize the ecological impacts of pharmaceutical compounds on biotic indicators and restore the river health condition. Some suggestive design guidelines for the CWs have also been presented to initiate the process.

Naturalization of treated wastewater by a constructed wetland in a water-scarce Mediterranean region

The effluents from conventional wastewater treatment plants (WWTP), even if accomplishing quality regulations, substantially differ in their characteristics with those of waters in natural environments. Constructed wetlands (CWs) serve as transitional ecosystems within WWTPs, mitigating these differences and restoring natural features before water is poured into the natural environment. Our study focused on an experimental surface-flow CW naturalizing the WWTP effluent in a semiarid area in Eastern Spain. Despite relatively low pollutant concentrations entering the CW, it effectively further reduced settled organic matter and nitrogen. Dissolved organic matter (DOM) reaching the CW was mainly protein-like, yet optical property changes in the DOM indicated increased humification, aromaticity, and stabilization as it flowed through the CW. Flow cytometry analysis revealed that the CW released less abundant but more active bacterial populations than those received. MiSeq Illumina sequencing highlighted changes in the prokaryotic community composition, with phyla Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria dominating the CW outflow. Functional prediction tools (FaproTax and PICRUSt2) demonstrated a shift towards microbial guilds aligned with those of the natural aquatic environments, increased aerobic chemoheterotrophs, photoautotrophs, and metabolic reactions at higher redox potentials. Enhanced capabilities for degrading plant material correlated well with changes in the DOM pool. Our findings emphasize the role of CWs in releasing biochemically stable DOM and functionally suited microbial populations for natural receiving environments. Consequently, we propose CWs as a naturalization nature-based solution (NBS) in water-scarce regions like the Mediterranean, where reclaimed discharged water can significantly contribute to ecosystem's water resources compared to natural flows.

Urban density and the urban forest: How well are cities balancing them in the context of climate change?

Urban forests are gaining recognition as a nature-based solution to climate change and other social-environmental issues in cities. Yet, the integration of urban forests may conflict with other climate measures such as urban densification, which may create hostile growing conditions for trees and lead to tree decline or loss. While previous studies have identified conflicts between densification and urban forests, there is a lack of research mapping the relationships among climate action, urban planning, and urban forest policies. This study involved semi-structured interviews with 14 key informants in Metro Vancouver, Canada, a rapidly-densifying region.Twenty-six trade-offs and 24 synergies were identified in five areas/sectors, such as (re)development and infrastructure. While strategic policies often highlighted synergies, policy implementation processes and outcomes often encountered trade-offs due to factors such as limited budgets and low political priority. Notably, most trade-offs and synergies were found in the same areas - (re)development and infrastructure - and shared the same contributing factors, such as political priority of urban forestry, suggesting areas of opportunity to transform trade-offs into synergies through appropriate planning and monitoring. The study also highlighted the need for further research on the interactions and impacts among municipal policies for more effective implementation and outcomes.

Plant-Based Biostimulants for Seeds in the Context of Circular Economy and Sustainability.

Plant-based biostimulants (PBs), agents rich in bioactive compounds, are emerging as key players able to sustainably improve plant growth and crop productivity to address food security. PBs are generally applied as foliar spray or soil irrigation, while more recently, the application as seed priming treatments is being envisaged as a highly sustainable method to also improve seed quality and germination. Therefore, this review proposes to explore the use of PBs for the seeds industry, specifically discussing about the relevance of product market values, sustainable methods for their production, why and how PBs are used for seed priming, and pinpointing specific strengths and challenges. The collected research studies indicate that PBs applied to seeds result in improved germination, seedling growth, and stress tolerance, although the molecular mechanisms at work are still largely overlooked. The high variability of bioactive molecules and used sources point towards a huge reservoir of nature-based solutions in support of sustainable agriculture practices.

Spatio-Temporal Pattern of Urban Green Space in Chengdu Urban Center under Rapid Urbanization: From the Policy-Oriented Perspective

Urban green space (UGS) is increasingly recognized as a nature-based solution to achieving urban sustainable development. Under rapid urbanization, greening policies are often the main driving factor behind the restoration or even growth of UGS. In this study, Chengdu, the pioneering “park city” in China, is chosen as a representative region. Based on land use/land cover (LULC) and normalized difference vegetation index (NDVI) data, indicators that can reflect both UGS quantity and quality are constructed and the spatio-temporal characteristics of UGS in original and expanding urban areas are also explored at different greening policy stages. The findings show that, from 2000 to 2022, the basic trend of UGS reduction during urbanization remained unchanged, despite the greening policies implemented in Chengdu. However, the original urban area has evolved into a new urban area. This has been achieved by integrating the expanded urban area with higher greening rates, resulting in the greening rate in 2022 (44.61%) being restored to the 2000 level (44.21%). The implementation of green policies in Chengdu is primarily reflected in improved UGS quality, especially in the stage of the ecological garden city construction (2008–2018). Specifically, the UGS quality in the original urban area has been improved by 25.25%. Overall, the UGS quality in Chengdu Urban Center has improved, changing from a medium level in 2000 to a medium-high level in 2022. The construction of a national demonstration zone of the park city provides an opportunity for the UGS quantity to increase and quality to improve in Chengdu in the future. However, effectively considering the development positioning of the Tianfu Granary to coordinate the relationship between UGS and high-quality farmland is a huge challenge for urban sustainable development in Chengdu.

Co-Production Boundaries of Nature-Based Solutions for Urban Regeneration: The Case of a Healthy Corridor

Co-production, rooted in public collaborative management (Ostrom, 1996) or science and technology (Jasanoff, 2013) evolution, has demonstrated its innovative and transformative character within participatory processes. However, there is little empirical evidence that scrutinises these contexts of interaction. Equality of partnership in many cases is used as a discursive rhetoric that seeks to prescribe co-production above any difficulty, uncertainty, conflict, or unwanted situation. As a starting point, our proposal considers co-production as a social practice, composed of multiple layers and different participatory processes, activities, and strategies. Grounded in co-production approaches, the study draws upon the ongoing evaluation findings of the European project URBiNAT, which focuses on inclusive urban regeneration through nature-based solutions. The qualitative methods of evaluation (interviews and participant observation), applied during the co-production activities in the city of Porto (Portugal), provide evidence of how the various stakeholders—elected politicians, citizens, technicians, and researchers—participate in the co-production dynamic. The boundaries of a multi-stakeholder process are revealed with the goal of implementing healthy corridors in peripheral neighbourhoods. The intended evaluation analysis lies in the techniques, the agents, the dynamics, the knowledge, and the degrees of co-production. This analysis will contribute to the lack of explicit consideration of the impacts of nature-based solutions in urban regeneration pathways, especially those related to the social fabric underlined in Dumitru et al. (2020).

Vallisneria spiralis L. adaptive capacity improves pore water chemistry and increases potential nitrification in organic polluted sediments

BackgroundMacrophytes may modify benthic biodiversity and biogeochemistry via radial oxygen loss from roots. This condition contrasts sediments anoxia, allows roots respiration, and facilitates aerobic microbial communities and processes in the rhizosphere. Simultaneously, the rhizosphere can stimulate anaerobic microorganisms and processes via exudates or by favoring the build-up of electron acceptors as nitrate. As eutrophication often results in organic enrichment in sediments and large internal nutrients recycling, an interesting research question is to investigate whether plants maintain the capacity to stimulate aerobic or anaerobic microbial communities and processes also under elevated organic pollution.MethodsA manipulative experiment was carried out under laboratory-controlled conditions. Microcosms containing bare sediments and sediments transplanted with the macrophyte Vallisneria spiralis L. were created. The effect of the plant was investigated on sediments with moderate (8%) and elevated (21%) organic matter content, after an acclimatization period of 30 days. Chemical and physical parameters, microbial community composition and the potential rates of nitrification, denitrification and nitrate ammonification were measured at two different depths (0–1 and 1–5 cm) after the acclimatization period to evaluate the role of roots.ResultsVallisneria spiralis grew and assimilated pore water nutrients at the two organic matter levels and vegetated sediments had always nutrient-depleted porewaters as compared to bare sediments. Nitrifying microbes had a lower relative abundance and diversity compared to denitrifying bacteria. However, regardless of the organic content, in vegetated sediments nitrifiers were detected in deeper horizons as compared to bare sediments, where nitrification was confined near the surface. In contrast, potential denitrification rates were not affected by the presence of roots, but probably regulated by the presence of nitrate and by root-dependent nitrification. Potential nitrate ammonification rates were always much lower (< 3%) than potential denitrification rates.ConclusionsVallisneria spiralis affects N-related microbial diversity and biogeochemistry at moderate and elevated organic matter content, smoothing bottom water–pore water chemical gradients and stimulating nitrification and nitrogen loss via denitrification. These results suggest the possibility to deploy V. spiralis as a nature-based solution to counteract eutrophication in freshwater systems impacted by high loads of organic matter, for example, downstream of wastewater treatment plants.

Boosting the resilience to drought of crop plants using wood distillate: A pilot study with lettuce (Lactuca sativa L.)

Increasingly severe drought driven by climate change is harming crop quality and productivity, making it crucial to find nature-based solutions like wood distillate (WD) to aid crops withstand these stressful conditions. This study investigated the effects of WD application on the growth and stress responses of lettuce (Lactuca sativa L.) under drought conditions. The experiment included periodic measurements of plant growth-related parameters and stress indices to evaluate the effectiveness of WD in mitigating drought-induced damage. The results showed a significant increase (13–26 %) in fresh biomass of the aboveground portion of lettuce treated with WD, indicating the potential of WD as a biostimulant to promote plant growth. In addition, treatment with WD led to a significant increase in total soluble protein content (14–28 %), showing a possible positive effect on protein synthesis. The enhancement of anti-radical activity (measured in terms of DPPH) following the application of WD up to 42 % reflected the ability of the plant to scavenge harmful reactive oxygen species and alleviate oxidative stress. The observed reduction (up to 19 % in comparison with control) in MDA content also confirmed the effectiveness of WD in protecting the integrity of plant cell membranes from oxidative damage. Despite the beneficial effects on anti-radical activity, the total content of the antioxidant compounds (phenols and flavonoids) decreased with the use of WD (5–14 %), most likely suggesting complex interactions between WD and the biosynthesis of these secondary metabolites. The study showed the positive effect of WD application on the growth and stress tolerance of lettuce plants under drought conditions. These results can provide new insights into sustainable agricultural practices and the potential application of WD as a nature-based and effective means to improve crop productivity, especially in water scarce areas.

Climate policies for carbon neutrality should not rely on the uncertain increase of carbon stocks in existing forests

The international community, through treaties such as the Paris agreement, aims to limit climate change to well below 2 °C, which implies reaching carbon neutrality around the second half of the century. In the current calculations underpinning the various roadmaps toward carbon neutrality, a major component is a steady or even expanding terrestrial carbon sink, supported by an increase of global forest biomass. However, recent research has challenged this view. Here we developed a framework that assesses the potential global equilibrium of forest biomass under different climate change scenarios. Results show that under global warming carbon storage potential in forest aboveground biomass gradually shifts to higher latitudes and the intensity of the disturbance regimes increases significantly almost everywhere. CO2 fertilization stands out as the most uncertain process, with different methods of estimation leading to diverging results by almost 155 PgC of above ground biomass at equilibrium. Overall, assuming that the sum of human pressures (e.g. wood extraction) does not change over time, that total forest cover does not change significantly and that the trend in CO2 fertilisation as it is currently estimated from satellite proxy observations remains, results show that we have reached (or are very close to reaching) the peak of global forest carbon storage. In the short term, where increased disturbance regimes are assumed to act quicker than increased forest growth potential, global forests might instead act as a carbon source, that will require even more effort in decarbonization than previously estimated. Therefore, the potential of forests as a nature-based solution to mitigate climate change brings higher uncertainties and risks than previously thought.

Potential of Nature-Based Solutions to Diminish Urban Heat Island Effects and Improve Outdoor Thermal Comfort in Summer: Case Study of Matadero Madrid

Urban heat island effects and climate change are climatic phenomena responsible for periods of extreme heat in summer which severely impact citizens’ well-being and health. In this alarming context which questions the livability of our cities, Nature-Based Solutions (NBSs) are considered an unavoidable component of the complex strategy in diminishing urban temperatures. The present work aims to show the relevance of NBSs in urban temperature regulation through the estimation of their potential to improve outdoor thermal comfort of the heritage site Matadero Madrid. To this end, this article evaluates the effects of a scenario combining different solutions including NBSs and identifies which solutions are the most effective. The results show that this scenario has an impact on direct solar radiation and wind speed but does not affect air temperature and relative humidity. Furthermore, even if this scenario combining a fabric canopy, tree canopy, and green area significantly improves thermal conditions, it does not allow us to reach an optimal level of thermal comfort for visitors. To consider the implementation of more meaningful interventions, existing legal, administrative, and cultural limitations of the case study should be omitted. This would enable us to identify which restrictions could be adapted, thus unlocking the adaptation potential of Matadero Madrid.

Comparison of cooling grey solutions in the sense-city urban demonstrator for adapting cities to heat waves

SummaryFaced with the increase in urban heat in summer, cities must quickly adapt by offering cool islands. If nature-based solutions are efficient and popular, other so-called grey solutions exist and can also provide solutions. In this paper we compare standard grey solutions in Sense-city, an urban demonstrator equipped with sensor, located in the scientific campus of Cité Descartes at Marne la Vallée. Our objective is on the one hand to compare the effectiveness of standard solutions over time, but also to study the ability of sense-city and its canyon street to study this phenomenon despite its relatively small size. MethodsIn this work we follow an experimental approach using a wide coverage of calibrated sensors deployed in Sense-city. We have conducted two measurement campaigns in July 2021 and July–August 2022 where we study the effectiveness of standard solutions (shading, white floor surface, street watering) to reduce the air temperature in the canyon street of sense-city. As the days are different, we compare the temperature difference in the street canyon equipped with these cooling solutions with that on the surrounding area. This method allows us to overcome daily variations. To interpret the results, we analyse the shades and we follow the temperature over time and not only during the hottest hours. We also calculate the UTCI (Universal Thermal Climate Index) to compare the perceived temperature. FindingsThe results show that despite its small size, the canyon street of sense-city behaves like a canyon street and that the measured temperature differences due to heat exchanges comply with physical laws and that the number and spatial distribution of sensors is validated. The Sense-city demonstrator can therefore be used to carry out thermal efficiency experiments. In addition, the method we used to compare cooling solutions allows us to limit the impacts due to slight daily variations. Finally, while watering is effective in rapidly lowering the temperature in the street, shading remains an optimal solution for the perceived temperature, even if it would be ideal to close them at the end of the day to allow air circulation.

Nature-based Solutions can help restore degraded grasslands and increase carbon sequestration in the Tibetan Plateau

The Tibetan grassland ecosystems possess significant carbon sink potential and have room for improved carbon sequestration processes. There is a need to uncover more ambitious and coherent solutions (e.g., Nature-based Solutions) to increase carbon sequestration. Here, we investigated the rationale and urgency behind the implementation of Nature-based Solutions on sequestering carbon using literature review and meta-analysis. We also project the changes in terrestrial carbon sink of Tibetan Plateau grassland ecosystems using model simulations with different future emissions scenario. The results show that the Nature-based Solution projects are expected to increase the carbon sink of Tibetan Plateau grassland ecosystems by 15 to 21 tetragrams of carbon by 2060. We defined a conceptual framework of Nature-based Solutions that integrates initiatives for the restoration of degraded grasslands and carbon sequestration. Our framework consists of four stages: theory, identification, practice, and goal. Traditional Tibetan knowledge plays an important role in reframing the proposed Nature-based Solutions framework. We also apply this framework to optimize ecological restoration techniques and projects and to evaluate the annual changes in the carbon sink under different socioeconomic pathway scenarios.

Computerized constructed wetlands allocation model (based on ecosystem services demand)

Egypt’s urban communities face many threats, including, pluvial floods, heat waves, and lack of publicly accessible urban green spaces. Nature-based solutions such as constructed wetlands (CWs) present a promising solution that could offer a wide range of ecosystem services (ES). However, the adoption of CWs is challenged by the lack of local planning guides and uncertainty about potential benefits. There are various models and tools available for quantifying and valuing ES, however, many of them are either highly complex or require extensive data and expertise. The aim of this paper is to develop a GIS-based multi-criteria decision model to select CW sites based on the supply and demand of ES. The model is to operate on three main stages: (i) demand: based on the need for risk reduction or benefit provisioning, (ii) potential sites (PSs): identify and score suitable sites for establishing a CW, and (iii) supply: define the service benefiting areas (SBA). An experimental approach is used, where the model is tested on New Damietta, an Egyptian Mediterranean city, proving the model is a reliable decision-making tool during preliminary urban planning stages due to its practicality, flexibility, and reasonable data requirements.

Nature-Based Solutions vs. Human-Induced Approaches for Alpine Grassland Ecosystem: “Climate-Help” Overwhelms “Human Act” to Promote Ecological Restoration in the Three-River-Source Region of Qinghai–Tibet Plateau

How climate change and human activities drive the evolution of the regional environment and where the quality of ecosystems improve or decline over time have become widespread concerns. In this study, we took the Three-River-Source (TRS) region of the Qinghai–Tibet Plateau as a case, aiming to identify and quantify the contribution of the natural and anthropogenic factors to the ecosystem changes over the past years from 1980 to 2018 using the methods of remote sensing and spatial statistical analysis. Based on the land cover map interpreted by reference to satellite remote sensing imagery data, we defined the Ecological Restoration Area Proportion (ERAP) as the bare land patch decrement to indicate the ecologically restored quantity in space. Assembling the restoration project information, we digitalized and vectorized the ecological Restoration Intensity (RI) including the spatial range and temporal duration. Combining the ERAP and the net primary productivity (NPP), which indicates the quantity and quality of ecosystems, respectively, the ecological asset Index (EAI) was developed and calculated. Having integrated the datasets of the vegetation monitoring, climatic factors, geographical factors, and human activities, we performed multi-variable analysis of the attribution of how the change in the EAI, the NPP, and the EAI have been affected by these factors together. The NPP of the middle and eastern parts of the TRS region has improved the most, as the average growth rate of NPP reached approximately 2.5 kg C/m2/10a. Due to such dynamic pattern, we found that human-induced re-vegetation has made limited contributions in our multi-regression model as the variance explained by the RI merely amounts to 4.4% to 8.8%, while the changes were mostly dependent on the regional temperature and the precipitation which contributed over 45% to the ecological restoration on average. It was summarized that “climate-help” overwhelms “human act” in such alpine grassland ecosystem. The regression results for the different aspects of the ERAP and NPP demonstrated that the ecological restoration project helped most in regard to ecosystem quality improvement rather than the restored ecosystem quantity. Our study has developed a comprehensive assessment methodology that can be reused to account for more ecological asset. The case is an example of an alpine ecosystem in which the success of ecological restoration needs favorable climatic conditions as supporting evidence for the nature-based solution.

Is Biomethane Production from Common Reed Biomass Influenced by the Hydraulic Parameters of Treatment Wetlands?

Treatment wetlands (TWs) are Nature-Based Solutions which have been increasingly used worldwide for wastewater (WW) treatment as they are able to remove mineral and organic pollutants through both physical and biochemical processes. Besides the reusable effluent, the TWs produce, as their main output, plant biomass that needs to be harvested and disposed of at least once a year with significant management costs and causing the TW to be temporarily out of service. This study aims (i) to evaluate the potential of TWs’ biomass for local energy production and (ii) to understand the effects of TWs’ hydraulic conductivity (Ks) on the biomass biomethane yield. Specifically, this was addressed by determining the Biochemical Methane Potential of common reed (CR) (Phragmites australis) samples collected at three harvest times from the 10-year-old horizontal subsurface treatment wetland (HSTW) used as a secondary WW treatment system for the IKEA® store situated in Catania (Eastern Sicily, Italy). Furthermore, the falling-head test was conducted to assess the hydraulic conductivity (Ks) variation in the hydraulic conductivity (Ks) of the HSTW, in order to understand its influence on the CR biomethane production. The average methane content values were 130.57 Nm3CH4/tVS (±24.29), 212.70 Nm3CH4/tVS (±50.62) and 72.83 Nm3CH4/tVS (±23.19) in August, September, October 2022, respectively. Ks was correlated with both dry matter (R2 = 0.58) and fiber content (R2 = 0.74) and, consequently, affected the biomethane yield, which increased as the Ks increased (R2 = 0.30 in August; R2 = 0.57 in September). In the framework of a circular economy, the results showed the successful possibility of integrating bioenergy production into TWs. The research could contribute (i) to encouraging plant operators to reuse biomass from TWs for local energy production and (ii) to help plant operators to understand Ks effects on the biomass biomethane yield in order to increase the sustainability of the system and to reduce the maintenance costs.