Regulating urban surface runoff through nature-based solutions – An assessment at the micro-scale. Zölch,T, Henze, L, Keilholz, P & Pauleit, S. Environmental Research, Volume 157, August 2017, Pages 135–14.
- Runoff after heavy rain events accounts for approx. 95% of total precipitation in highly sealed urban areas.
- By enhancing water storage capacities green infrastructure reduces runoff by max. 14.8% compared to the baseline.
- Green roofs and trees both show to be effective but due to different functions.
- The reduction of runoff is larger with higher shares of green cover in the case area.
Urban development leads to changes of surface cover that disrupt the hydrological cycle in cities. In particular, impermeable surfaces and the removal of vegetation reduce the ability to intercept, store and infiltrate rainwater. Consequently, the volume of stormwater runoff and the risk of local flooding rises. This is further amplified by the anticipated effects of climate change leading to an increased frequency and intensity of heavy rain events. Hence, urban adaptation strategies are required to mitigate those impacts.
A nature-based solution, more and more promoted in politics and academia, is urban green infrastructure as it contributes to the resilience of urban ecosystems by providing services to maintain or restore hydrological functions. However, this poses a challenge to urban planners in deciding upon effective adaptation measures as they often lack information on the performance of green infrastructure to moderate surface runoff. It remains unclear what type of green infrastructure (e.g. trees, green roofs), offers the highest potential to reduce discharge volumes and to what extent.
Against this background, this study provides an approach to gather quantitative evidence on green infrastructure’s regulation potential. We use a micro-scale scenario modelling approach of different variations of green cover under current and future climatic conditions. The scenarios are modelled with MIKE SHE, an integrated hydrological modelling system for building and simulating surface water and groundwater flow, and applied to a high density residential area of perimeter blocks in Munich, Germany. The results reveal that both trees and green roofs increase water storage capacities and hence reduce surface runoff, although the main contribution of trees lies in increasing interception and evapotranspiration, whereas green roofs allow for more retention through water storage in their substrate. With increasing precipitation intensities as projected under climate change their regulating potential decreases due to limited water storage capacities. The performance of both types stays limited to a maximum reduction of 2.4% compared to the baseline scenario, unless the coverage of vegetation and permeable surfaces is significantly increased as a 14.8% reduction is achieved by greening all roof surfaces.
The authors conclude that the study provides empirical support for the effectiveness of urban green infrastructure as nature-based solution to stormwater regulation and assists planners and operators of sewage systems in selecting the most effective measures for implementation and estimation of their effects.
Urban green infrastructure as nature-based solution to regulate surface runoff becomes increasingly important, as climate change and urbanisation alter the urban water balance. The present study assessed the performance of two urban green infrastructure (UGI) types, trees and green roofs, on relevant hydrological processes, especially surface runoff. The two measures were applied in scenarios of different greening quantity and for heavy rain events of different intensities as projected for the future. This scenario approach revealed that both trees and green roofs contribute positively by interception, evapotranspiration and infiltration. Differences in their performance showed to be dependent on the greening quantity, share of permeable surfaces leaf area index (LAI) and finally, intensity of the rainfall event. Generally, their effectiveness remains low under heavy rain events, unless a significant proportion of the case area is greened to provide sufficient water storage capacities (Artmann, 2014).
For urban planning the presented results have practical implications for the selection of UGI types to reduce surface runoff volumes and in consequence reduce discharge loads, the sewage system has to handle. An effective nature-based solution increases the storage capacities within the area of interest as much as possible, while using open spaces that have not been used previously and/or while providing benefits to other areas of urban planning. Trees increase the storage capacity mainly by intercepting and evapotranspiring rainwater, their infiltration capacity is limited to the tree pits. But trees can normally not be implemented in large quantity in dense urban areas due to their requirements of open space. Green roofs on the other hand, provide storage capacity mainly by retaining rainwater in their substrates and can be implemented at larger scale on previously unused roof surfaces.
Furthermore, both types are multifunctional and can provide co-benefits for urban planning. The approach represents a first step in allowing planners as well as operators of sewage systems to estimate reductions in runoff volume when locally implementing UGI measures. These estimations could be further improved by integrating additional stormwater management practices and the drainage system in more detail into the modelling setup. Thus, conducting a larger systematic study of UGI scenarios would allow for including e.g. more UGI types, different species and LAI values as well as planting conditions. Such a study could enhance the provision of empirical evidence for climate resilient urban planning.
In March 2013 the Landscape Institute published an updated Mission Statement, ‘Green Infrastructure: An integrated approach to land management’. The document was described as,
“An opportunity to showcase a range of successful strategic GI work and completed
projects. The aim is to give public and private sector bodies, clients and natural and built environment professionals fresh insights into the benefits GI can bring by creating multifunctional landscapes and show how people can collaborate to deliver it.”
Research: Collentine, D. & Futter, M.N. (2016). Realising the potential of natural water retention measures in catchment flood management: trade-offs and matching interests. Journal of Flood Risk Management. DOI: 10.1111/jfr3.12269.
Natural water-retention measures, which ‘keep the rain where it falls’, have great potential to be used as part of flood-risk management plans. But their benefits for downstream urban areas can bring costs to the upstream agricultural areas where they are installed. The researchers suggest that we need new and/or improved policies and institutions to oversee the trade-offs and benefits for agriculture and flood management, and a better scientific understanding of the measures’ likely impact on urban flood risk.
The analysis, conducted by academics in Sweden, draws on various studies to discuss the many benefits of natural water-retention measures and how to encourage their uptake. Floods, which have caused annual economic losses of €4 900 million in Europe, are a serious problem. Natural water-retention measures could play an important role in managing floods, the researchers say, and help meet the goals of the EU’s Floods Directive and Water Framework Directive. These nature-based solutions store rainfall and allow it to evaporate back into the atmosphere to help prevent water flowing into urban areas, where it can cause the greatest damage.
Nature based water-retention measures are a key example of how green infrastructure can work alongside traditional grey infrastructure (e.g. flood gates). They take many forms, from small green roofs to large forests, and bring multiple benefits. As well as reducing flood risk, they can have value for biodiversity, recreation and water quality because they reduce soil erosion and can prevent agricultural pollution running into rivers.
However, this multi-functionality may also act as a barrier to their uptake. Because they bring benefits that fall under different policy areas, it is not necessarily easy for decision makers to determine who should pay for these measures. For some measures, the effect on flood risk may be an additional, secondary benefit — as in the case of agricultural buffer zones, which are primarily intended to reduce fertiliser run-off.
Alongside flood-management benefits, measures installed on upstream agricultural land can also lead to trade-offs, notably reduced crop yield. This loss occurs either because cropland is replaced by the measures or because soil in fields becomes too wet. A payment-for-ecosystem-services (PES) model could, therefore, be used to finance natural water-retention measures, possibly through national agri-environmental schemes. Research from the USA has indicated that it is less costly to pay farmers to temporarily flood their land upstream, than it is to pay for urban damage downstream.
Other barriers to widespread uptake of natural water-retention measures include specific knowledge gaps. There is plenty of evidence to show the effectiveness of individual natural water-retention measures, particularly in small catchments. Computer-modelling studies suggest natural water-retention measures could contribute to downstream flood risk reduction, but there is a lack of real world studies which show how to incorporate such measures into flood-risk management plans and their likely impact on downstream urban flood risk. Such studies are needed to encourage further uptake by decision makers and land managers.
The exact area of responsibility of decision makers with regard to flood-risk management also remains unclear. As such, water policy at the national level is accountable to EU water directives and national decisions must be consistent with the decisions made at the EU level. This is also true for regional-level policy, which is based on national policy and, similarly, local decisions are founded on regional policy. Unfortunately, this set of embedded decisions seems to break down with flood-risk management and has led to a lack of distinction between jurisdictions. Each jurisdiction attempts to reduce flood damage within a limited area and thus tends to focus on the use of preventive structural measures, such as dams or retaining walls, rather than measures to reduce flooding (1).
The authors recommend that institutional structures and mechanisms are created or enhanced to oversee the urban/rural trade-offs that natural water-retention measures may bring, to match potential costs with benefits and ensure an appropriate compensation scheme is put in place; for example, one which links PES with flood-risk management plans.
1. This shortcoming should normally be addressed by the inclusion of a river basin approach within the flood risk management plans: http://ec.europa.eu/environment/water/index_en.htm
In his paper, ‘Constructing Landscape by Engineering Water’, Antoine Picon states that, “Technology used to be defined as an action exerted by man on nature. Nowadays we may wonder, especially in the urban context, whether man is adapting the very concept of nature to cope with the challenges we face.”
Picon, Professor of the History of Architecture and Technology at the Harvard Graduate School of Design, refers to “techno-nature”, a phrase he uses to describe the blurring between nature and the modern day, man-made urban realm. He claims that this is most prominent in the design of remedial landscapes . Historically, engineered hydraulic designs made clear distinctions between natural and man-made interventions – canals, aqua-ducts, locks and water treatment and storage was visibly constructed and segregated. Nowadays however, projects are often a combination of hard and natural engineering with a stronger reliance on nature based solutions for water management.
“Blending the natural and the artificial is not easy to reconcile with the public’s desire for close contact with natural elements and ambiances. Part of the challenge for landscape designers is to propose sequence that function with a harmonious combination of natural appearances and unavoidable artificiality.” Antoine Picon, ‘Constructing Landscape by Engineering Water’
Source: Institute for Landscape Architecture, ETH Zurich (ed.), Landscape Architecture in Mutation: Essays on Urban Landscapes, Zurich: gta Verlag, 2005, pp. 99-115.
Such as the project on the banks of the River Seille at Metz, France. Here everything is artificial – the project focuses on the development of a new water catchment basin created by a new branch of the river – ‘giving the Seille River an extra arm’ – to assist regulating the Seille River’s hydrography. The project provides a new ‘natural element’ on the edge of the city.
Parc de La Seille – METZ (Moselle)
Completion year 2003
Contracting Authority Municipality of Metz
Mission Creating an urban park featuring an advanced environmental approach
Project Management Team Landscape architects and designers Jacques Coulon (mandated agent), Landscape architects and designers Laure Planchais, Ecological engineers Sinbio, Civil works engineers Ingerop, Light designers Coup d’Eclat
Surface area 20 hectares (excluding the Seille River)
Budget €6m exc. VAT
Ratio €30 exc. VAT per m²
The Parc de La Seille was intended to be a space widely open to the skies, highlighting the topographical features of the banks of the river that runs through it by forming links with the surrounding existing and future urban landscape. Significant levelling has been performed to open up the Seille River which had until then been channelled, as well as shaping the hills that link the park to the future slab-mounted Amphitheatre district. A vast prairie stretches at the foot of the hills, which is used to host various activities.
The park has a number of purposes:
- “Reclaiming” the riverside environment
- Regulating the Seille River’s hydrography
- Collecting water for the future Amphitheatre district
- Forming a key area in the city, suitable for hosting sports and cultural events.
By increasing the areas liable to flooding, and giving the Seille River an extra arm, the park solves all hydrological issues and gains an alluvial setting. The water gardens provide a contrast with the dry hill gardens, encouraging some diversification among the possible biotopes in the area.
As a more urban feature, the esplanade hosts those sports and cultural events that are more spectacular. It starts out inside the Amphitheatre district by the Metz Centre Pompidou, and ends up as a platform overlooking the Seille River, thereby accentuating the bond between the district and the river.
Over 20 hectares, the park offers areas of flowering plants, wet and dry meadows, vineyards and hop growing on hillside, fruit trees and others, sports and play areas plus many trails.
In addition to being of value in their own right, natural systems and processes provide a broad range of goods and services which help to support human health, well-being and economic success. Ecosystem services are the benefits which nature provides for human well-being, society and the economy. They include:
- Provisioning services: the goods people obtain from ecosystems, including food, water, fuel, raw materials and genetic resources
- Regulating services which control conditions, including the processes that regulate the climate and water flows; air, water and soil quality; pollination; and pests and diseases
- Cultural services, including aesthetic, spiritual, educational and recreational benefits
- Supporting services, which provide the basic infrastructure for life, including photosynthesis, nutrient cycling, and soil formation
Understanding and working with nature where possible will enable us to achieve more sustainable outcomes. This means taking a more proactive approach than assessing and mitigating the environmental impacts of policies, strategies and projects through formal processes including Strategic Environmental Assessment, Sustainability Appraisal, Environmental Impact Assessment and Habitat Regulations Appropriate Assessment.
The ecosystem approach is a holistic and inclusive approach to planning and decision making, which takes account of the benefits and services we derive from nature and seeks to maintain or enhance them. It involves understanding the ecosystem services provided across a given area; valuing them appropriately; and involving the relevant stakeholders to make balanced and effective land management decisions, based on the best possible understanding of the implications.
It is important that ecosystem services are accounted for in decision-making for their own sake, but in these economically constrained times, applying the ecosystem approach will also help ensure that limited funds are targeted at the interventions which will deliver the maximum benefits to the environment, people, and the economy.
The ecosystem approach has been fundamental to the development of the Partnership Management Plan for the South Downs National Park. An overview of the ecosystem services provided by the National Park is included in the introduction to the document, and this understanding informs the policies on farming, forestry and woodland, water, tourism and other aspects of management.
The ecosystem approach is reflected in major projects in the National Park, including the South Downs Way Ahead Nature Improvement Area. This £3 million project is bringing together farmers, community groups, government bodies, research organisations, charities and local businesses to protect, restore and reconnect endangered chalk down land, enhance biodiversity and improve water quality.
In addition to informing planning and decision making, applying this kind of thinking can help to identify, develop and raise funding for projects which support adaptation to climate change and sea-level rise while enhancing the natural environment and benefiting local communities. The Medmerry coastal realignment scheme in Sussex is a great example of what can be achieved by working with nature (see case study).
When the social and economic benefits provided by the natural environment are clear, their value can be estimated and used to make the business case for funding or direct payments to those who help to maintain them.
Payments for Ecosystem Services (PES) schemes provide incentives to farmers and landowners to manage the land in a way which will deliver these services to an agreed standard through a voluntary agreement. A number of pilot studies have been undertaken across England, including the Slowing the Flow project in Pickering, North Yorkshire, which sought to reduce flood risk downstream and improve water and soil quality, by changing land management practices and planting additional woodlands to slow the flow of water through the river catchment. This approach builds on established schemes such as Environmental Stewardship and the Woodland Grant Scheme which are already widely taken up by landowners.
Case study: Medmerry managed realignment, West Sussex
The following case study is part of the No Regrets: Planning for Sea Level Rise and Climate Change and Investing in Adaptation Good Practice Guide sponsored by the Southern Regional Flood and Coastal Committee, August 2015. Local authorities and other organisations involved in planning, decision-making and infrastructure investment are encouraged to follow these case studies and plan for the long-term future of coastal communities in the South East of England and further afield.
Medmerry is the largest coastal realignment scheme on the open coast in the UK. It is sited on the west side of the Manhood Peninsula, which juts out into the English Channel south of Chichester. This is a flat coast line protected by shingle beaches, which are vulnerable to breaching and over-topping in storm conditions, resulting in regular flooding by the sea. Rather than building up the beaches to ever higher levels, as sea levels rise, the Agency decided to work with nature.
The scheme involved building up some 7km of new earth walls inland, breaching the existing shingle beach and forming a large new saltmarsh habitat. This helps to absorb wave energy and manage flood risk for 350 homes, two holiday parks, and a sewage treatment works. It also provides important compensation for loss of intertidal saltmarsh habitat elsewhere, allowing other flood defence schemes to proceed around the Solent.
The new habitat is now an RSPB Reserve with extensive walks and cycle tracks for people to enjoy and benefits for local businesses. It is a model for win-win climate change adaptation, combining improved flood defences with new natural habitats and opportunities for recreation and business on the coast.
The £28 million scheme was carried out by the Environment Agency from 2011 to 2013. At all stages, the scheme was developed in close consultation with a stakeholder group embracing a wide range of local interests.
Urban areas have a variety of environmental challenges, ranging from pollution to the effects of climate change. Nature-based solutions can provide an effective way to tackle these issues, whilst also generating social and economic benefits.
As urban populations grow and climate patterns shift, the need for such measures is expected to increase, according to Gorm Dige, project manager for territorial environment, policy and economic analysis with the European Environment Agency (EEA). By 2020 it is estimated that almost 80% of EU citizens will be living in cities.
The potential benefits of applying ‘nature’ solutions in towns and cities are manifold. They include: improving human health and well-being; encouraging economic development and investment; providing adaptation to predicted changes in climate; regeneration of previously developed land; promoting wildlife and habitats; and encouraging stronger and safer communities.
“Integration of urban green space with the built environment that surrounds it is crucially important if the benefits are to be maximised,” says Mr Dige. Communicating these benefits is also vital: “The real potential of such green spaces will only be realised if the activities or operations undertaken are supported by the whole local community.” He adds that creation and management of urban green spaces should be integrated with traditional land development and built infrastructure planning in order to achieve the potential benefits.
Role of green and blue infrastructure
Green (and blue) infrastructure is an important aspect of nature-based solutions, linking urban areas to the countryside and providing numerous environmental, social and economic benefits. It includes open land, woodland, private gardens, trees on streets, green roofs and parks, as well as ‘blue’ spaces such as wetlands, swales, ponds and temporary flood storage areas. Green infrastructure can be strategically planned and delivered on a range of scales to provide useable space with support for natural and ecological processes.
Gorm Dige contrasts this with ‘grey’ infrastructure, such as roads, piped sewer and water systems, dikes and concrete walls to combat flooding. “For example, single-purpose grey storm water infrastructure is largely designed to move urban storm water away from the built environment,” he explains. “Whereas green infrastructure reduces and treats storm water at its source, whilst also delivering many other environmental, social and economic benefits that promote urban liveability and add to the bottom line.”
The list of benefits for urban areas provided by green infrastructure is long, according to Gorm Dige. Some of these include:
- higher real estate prices;
- improved well-being and recreational opportunities;
- reduced energy consumption;
- improved pedestrian safety and traffic calming;
- lower costs for wastewater treatment;
- increased biodiversity;
- a more liveable habitat for birds, native plants and residents;
- enhanced community spaces and more appealing streets;
- improved street conditions for cyclists and pedestrians;
- reduced storm water run-off through soil and vegetation;
- cleaner groundwater;
- noise reduction;
- reduced urban heat (the heat island effect);
- and improved air quality.
On top of that, green infrastructure has an important role to play in supporting the adaptation of urban areas to climate change. It can provide shade and cooling in warm weather as well as wind interception and insulation in winter. Green infrastructure may also mitigate the risks from climate change-induced reductions in air and water quality. In addition, it can provide a buffer for habitats and species, whilst contributing to sustainable urban drainage and controlling upstream water flows to reduce flood risk.
“Effectively harnessed, green infrastructure also has real potential for informing people about climate change,” notes Mr Dige. “Green spaces can be used to promote an appreciation of the impacts of climate change and the lifestyle changes needed to reduce its effects and/or to adapt to them.”
Green infrastructure is anchored in the EU’s 2020 Biodiversity Strategy. However, “it is important to recognise that it can make significant contributions to other EU policy objectives on e.g. regional and rural development, health, climate change, disaster risk management, energy, agriculture, forestry and the environment”, says Mr Dige. He adds, “Green infrastructure has the potential to offer win-win solutions by tackling several problems at the same time. It is therefore a valuable policy tool to promote smart and economic sustainable growth.”
Contribution of LIFE
The LIFE programme has already made a significant contribution in the area of nature-based solutions, according to the EEA project manager, for instance by supporting connectivity of species and habitats, restoration of ecosystem functions, adaptation to climate change and building green infrastructure into urban planning.
It is difficult to calculate the benefits of such measures in monetary terms, but Mr Dige believes that LIFE project results could be consolidated and used to “showcase the multi-functional opportunities that green infrastructure provides to communities in urban settings”. This would involve analysing projects to determine their quantitative benefits, for example in terms of improving water retention, air quality, noise reduction, increasing tourism and recreational opportunities, insulation of buildings (green roofs), cutting energy demand and reducing urban heat island effects. “Monetary values of these benefits would assist decision-makers and urban planners in better comparing grey and green infrastructure solutions, ” he says.
There are several other areas that Gorm Dige believes could be fruitful for future LIFE projects. For example, encouraging developers and urban planners to rethink conventional approaches in order to tackle increased heavy precipitation and flooding in cities. New projects could also build on the results and findings of previous ones. For instance, finding more cost-effective storm-water management strategies in cities by using green infrastructure practices (i.e. through more soil and vegetation), and investigation of whether green roofs and trees in urban streets can reduce energy costs (e.g. by providing insulation or cooling, depending on the weather conditions).
He concludes, “With mounting investments required to repair and maintain the ageing stock of grey infrastructure, and increasing environmental pressures from expanding urbanisation, ecosystem services that have been seen as free are now entering authorities’ planning and management equations at town, city and regional level.” Compounded by “increasing regulatory pressure to address water and air quality, the need to anticipate and adapt for localised – if yet uncertain – impacts of climate change, and the drive for economic competitiveness, all with ever more constricted finances”, communities, cities and regions across Europe are increasingly assigning higher priority to nature-based solutions.
Further information on the role of green infrastructure in mitigating the impacts of weather- and climate change-related natural hazards is available in this recently released EEA report.
‘Towards an EU Research and Innovation policy agenda for Nature-Based Solutions & Re-Naturing Cities’ – the Final Report of the Horizon 2020 Expert Group on ‘Nature-Based Solutions and Re-Naturing Cities’ published by the European Commission’s Directorate-General for Research and Innovation, Climate Action, Environment, Resource Efficiency and Raw Materials.
- Nature-based solutions – what are they?
Nature-based solutions aim to help societies address a variety of environmental, social and economic challenges in sustainable ways. They are actions which are inspired by, supported by or copied from nature. Some involve using and enhancing existing natural solutions to challenges, while others are exploring more novel solutions, for example mimicking how non-human organisms and communities cope with environmental extremes. Nature-based solutions use the features and complex system processes of nature, such as its ability to store carbon and regulate water flow, in order to achieve desired outcomes, such as reduced disaster risk, improved human well-being and socially inclusive green growth. Maintaining and enhancing natural capital, therefore, is of crucial importance, as it forms the basis for implementing solutions. These nature-based solutions ideally are energy and resource-efficient, and resilient to change, but to be successful they must be adapted to local conditions.
- Key opportunities for research and innovation policy on nature-based solutions. The expert group identified four goals:
- Enhance sustainable urbanisation – Currently, 73% of Europe’s population live in cities and this is projected to increase to 82% by 2050, resulting in over 36 million new urban citizens . This will pose a range of challenges for cities, including resource availability and equitable economic growth. The quality of urban environments is also at risk, necessitating their sustainable development and regeneration in order to provide citizens with healthy and liveable conditions.
- Restore degraded ecosystems – In Europe, significant areas of ecosystems are being lost or degraded as a result of human activities. For example, between 60% and 70% of European wetlands have been completely destroyed.The drivers of loss and degradation vary according to the ecosystem and location, but the key pressures include agricultural intensification, grey infrastructure expansion, pollution of brownfield sites, hydrological modifications to water bodies, the intensification of forestry practices and, generally speaking, climate change
- Develop climate change adaptation and mitigation – Addressing climate change is a challenge as its impacts on Europe are likely to increase and it affects all aspects of the environment, economy and society. For example, the annual damage of climate change to the EU economy, measured as GDP loss from today’s conditions, could be between €20 billion for a 2.5°C scenario and €65 billion for a 5.4°C scenario with high sea level rise.
- Improve risk management and resilience – Europe is exposed to a range of natural and technological hazards, including drought, extreme temperatures, floods, industrial and transport accidents, landslides and avalanches, storms, volcanoes and wildfires. In the EU, between 2002 and 2012, numerous such events generated 80,000 fatalities and €95 billion in economic losses.
The restoration of the floodplain of the Noordwaard polder, the Netherlands, will provide climate change-related flood protection, improve the environmental quality for people and nature, increase recreational facilities and boost the economy. Both photos show the situation after depoldering, which has left more room for the river.
- Seven priority nature-based research and innovation actions to meet societal challenges in the above four goals have been identified:
- Urban regeneration through nature-based solutions – Changes in land use, neglected land and abandoned areas are challenges for many cities. Urban regeneration through nature-based solutions offers a context for innovative interventions for green growth.
- Nature-based solutions for improving well-being in urban areas – With millions more people needing housing, services, workplaces, infrastructure and institutions by 205020, the potential impacts of development decisions are unparalleled. By integrating nature based solutions into urban design and planning, increasingly large and dense cities can improve human health and well-being, while offering ecological and economic co-benefits.
- Establish nature-based solutions for coastal resilience – Coastal habitats are iconic and of considerable economic and social importance across the EU, protecting against floods and erosion, while providing livelihoods for many individuals through tourism and fishing.
- Multi-functional nature-based watershed management and ecosystem restoration – Watershed management and restoration using nature-based solutions can help to reduce the risk of floods and droughts, while improving water quality and quantity.
- Nature-based solutions for increasing the sustainable use of matter and energy – Nature-based solutions can decrease resource demand through energy and matter-efficient processes. In cities, green spaces and green roofs provide natural cooling or insulation.
- Nature-based solutions and the insurance value of ecosystems – The insurance value of ecosystems has to date been largely overlooked in research and practice and mostly discussed in relation to its role as a metaphor for the value of resilience.
- Increase carbon sequestration through nature-based solutions – Over the last 30 years, terrestrial and freshwater ecosystems have stored about a quarter of human generated CO2 emissions.