Water is a fundamental component of the urban ecosystem. It is a form of nature in the city that has multiple anthropic uses and must be managed in order to control potentially damaging effects (flooding, soil and water contamination, etc.). This issue can be approached from the point of view of both the environmental and social sciences, or a combination of these to offer a systemic overview of the subject. In cities, water-related NBS refer to certain well identified forms: constructed wetlands, swales, de-sealed areas, reopened streams, the remeandering and reprofiling of rivers, etc. The challenges and benefits of restoring the water cycle at a neighbourhood scale, such as improving biodiversity and managing flood risks, are well documented. This session will focus more on the NBS where water is "hidden". Indeed, some NBS, not directly associated with water, are nevertheless highly dependent on it. These are NBS that involve vegetation, especially when it is irrigated: green spaces, vegetable gardens, etc. Also applicable are NBS participating in urban cooling by means of shading effects, and includes the evapotranspiration process. Such NBS are often characterized in relation to their use of vegetation, but the process also relies on the availability of water. In order to develop a more systemic vision of water management, the session will also address the questions that are raised by the human and social sciences. Water-related NBS can also involve conflicts of usage: irrigation and water sharing, layout of renatured rivers, etc. The session will also focus on the perceptual aspects of this type of NBS such as safety and associated nuisances (mosquitoes, odours, etc). Scientific papers and policy briefs proposed by researchers and practitioners will be welcomed.
Stakeholders are increasingly realizing advantages of Nature-Based Solutions (NBS) to rapidly adapt to changing climate patterns and related impacts such as flooding, landslides, mudflows or rockfalls while providing a multitude of co-benefits such as an increased landscape value for society and biodiversity. Collaborative planning and co-design approaches such as using Living Labs can help to overcome bottlenecks when implementing measures and provide common ground to provide space for new ideas, to promote innovation and to develop solutions with high acceptance. While co-design and implementing NBS has already been applied and are well documented for urban areas, muss less attendance is given to mountain areas, although these areas are much more effected by changing climate and resulting increase in severe weather events.
In our case study analysis from the EU-funded H2020 project PHUSICOS, we present stakeholder views on NBS from rural and mountain areas in the Pyrenees (France, Spain and Andorra), the Serchio River Basin (Italy) and in Gudbrandsdalen (Norway). The case sites have to tackle challenges such as avalanches, landslides, rockfall and debris flows (Pyrenees), reducing the risk of flooding and enhancing water retention capacities (all demonstrator cases) and reducing runoff and debris flow from agricultural land into waterbodies (Italy).
Besides literature reviews on collaborative planning on NBS and neighboring concepts, a series of in-depth interviews with selected stakeholders as well as standardized surveys are conducted throughout the lifetime of PHUSICOS. They intend to provide insights on stakeholder views, perceptions, awareness and expectations on NBS and the connected collaborative planning and co-design processes to establish tailored NBS solutions in the different study areas.
Outcomes from the first series of in-depth interviews and first standardized surveys indicate that despite the importance of NBS on political and research agendas, stakeholders are less familiar with the NBS concept. It was mainly encountered within river restoration measures. The main interest for implementing NBS in rural mountain areas was to reduce risks of natural hazards. A very important aspect for stakeholders was to find solutions that were attractive and interesting from an economical point of view such as creating new viable business models for farmers and landowners. Less importance was seen in a multitude of benefits which is often the most important aspect for NBS implementation in urban settings.
With a lack of knowledge and a proof of concept that NBS can reduce the risks of natural hazards, the Living Lab processes in PHUSICOS were seen most important to engage stakeholders and provide learning opportunities about NBS. Especially “hands-on” cases” were considered very important to demonstrate the durability, viability and reliability of such solutions and to overcome skepticism.
With many expectations to NBS and the Living Lab processes expressed by the interviewed stakeholders in the PHUSICOS project, it will be particularly interesting to follow stakeholder attitudes and perceptions on NBS throughout the project lifetime. Learning, building trust and intensive in-depth collaboration processes seem to be the key elements for triggering action, mainstreaming NBS and gaining more acceptance of NBS over traditional grey solutions.
As the world’s population keeps growing, and, at the same time, the percentage of people living in urban areas is rising, cities become denser, and overbuilding of hard surfaces is causing the depletion of urban greenery, exacerbating the urban heat island and increasing urban vulnerability due to climate change (Victorero et al., 2015; Weinmaster, 2009). Green walls are a nature-based solution attracting increasing interest for architectural green cladding. Green walls bring the natural environment into building technological systems in the urban landscape (Kmieć, 2014; Virtudes & Manso, 2016), forming a convenient solution to the above-mentioned problems.
There are different types of green walls, such as direct or indirect green facades and continuous or modular living walls (Palermo & Turco, 2020; Pirouz et al., 2020).
In this study, a modular living wall was designed and installed in Nicosia, Cyprus, characterized by a Mediterranean semi-arid climate. The modular living wall was assessed for its hygrothermal and sound insulation performances with an in-field experiment that compared the performance of the modular living wall against a control wall. During the experiment, (dry-bulb) air temperature, relative humidity, and sound level were collected for four weeks at the modular living wall and the control wall. The surface temperatures of the two façades were also acquired using infrared thermal photography. Moreover, in this study, a five-stage methodological framework for the plant selection phase of a green wall installation was developed and applied.
The results of this study always indicate lower dry-bulb air temperature behind the modular living wall, with a maximum reduction of 7.9 °C, due to shading from the green wall (Cameron et al., 2014) and evapotranspiration from the plants and the soil (S. K. Gupta, 2018). Also, a decrease in the sound level behind the MLW was measured with a maximum of 5.1 dB. Relative humidity was consistently higher (up to 6.6%) in the air cavity between the modular living wall and the building fabric but consistently lower than about 70%. On the contrary, absolute humidity was always lower in the air cavity, with a maximum difference of 8.6 g/Kg. The surface temperature of the modular living wall was observed to be, during the day, up to 27 °C lower than that of the control façade, which was in the same location and exposure. Furthermore, from the surface temperature monitoring of the foliage, it was found that foliage with a higher leaf area index is more effective in reducing the green wall’s surface temperature that, for the experiment conducted, it amounted to up to 5.8 °C.
Overall, the modular living wall proved to be beneficial for protecting the building materials and envelope components from high solar radiation and ambient temperature and increasing the cooling energy savings, while it requires water for plant irrigation.
This study was developed to contribute to an ongoing collaboration between The Cyprus Institute and Politecnico di Milano on nature-based solutions adopted for climate-change mitigation and adaptation, thanks to the contribution of the industrial company ItalMesh.
Sub-Saharan Africa (SSA) is the region most vulnerable to climate change and related hydro-meteorological risks (HMRs). These risks are being worsened through rapid urbanization and the depletion of green spaces with their regulating ecosystem services (ESSs). The potential of nature-based solutions (NBS) to mitigate natural hazards is increasingly recognized in the Global North; however, its application in urban areas of SSA still needs to be systematically explored to promote its uptake in the sub-region. We therefore conducted this multidisciplinary systematic review following the PRISMA protocol to assess 1) the extent of uptake of NBS for HMR mitigation in urban SSA, 2) the location of NBS in relation to location of risks, 3) the specific practices in use and 4) the benefits being derived through ESSs generated and livelihood opportunities created. After searching scientific journal databases, including Scopus, Science Direct and Web of Science; websites of 12 key institutions, including UN agencies and Local Governments for Sustainability; and 11 NBS databases, 45 papers were identified for analysis.
We found at least one reported NBS in 70.8% of SSA countries across 83 different locations. 62.2% of the papers however studied locations in South Africa, Kenya, Tanzania and Nigeria only, while the most studied cities were Dar es Salaam in Tanzania (n=6) and Kampala in Uganda (n=3). Sixty-six different NBS practices were identified, most of which were implemented for mitigating floods (n=44). We also found that NBS are implemented where risks are, but not where they are most severe. Among the most at-risk countries like Somalia, South Sudan and Mozambique, only Mozambique reported on NBS (n=2). Furthermore, blue and green NBS practices like mangrove restoration, wetland restoration; reforestation, urban forests; agroforestry and conservation agriculture are most common for floods, extreme heat and drought mitigation, respectively. These NBS practices also provided ESSs, including 15 regulatory, 5 provisioning and 4 cultural ESSs. Also, 4 in 5 NBS created livelihood opportunities, mostly green jobs in disciplines like horticulture, forestry, market gardening and eco-tourism.
We make several conclusions. First, that reported uptake of NBS for HMR in SSA remains low however, there could be more ongoing NBS, especially at the local level, that are unreported. Second, NBS are being implemented where risks are but not where they are most severe. Third, it is not too late for SSA to develop in a climate-resilient way due to the proliferation of blue and green NBS. This will help to avoid repeating past mistakes in the Global North that led to depletion and dwindling of green and blue spaces. Fourth, NBS could help address some of the major developmental challenges that confront SSA, including issues of food and water insecurity and unemployment, aside from climate change and the associated risks.
We recommend NBS to be mainstreamed into urban planning, for NBS to be improved through a co-created citizen science approach and for NBS that drive urban and peri-urban agriculture to be prioritized. Furthermore, we recommend that knowledge transfer opportunities between SSA and Europe be explored.