Green infrastructures towards resilient cities
According to the United Nations, 68% of the world population is projected to live in urban areas by 2050. Understanding the key trends of urbanization is crucial to proceed with the implementation of the 2030 Agenda for Sustainable Development, including Sustainable Development Goal 11 – to make cities and human settlements inclusive, safe, resilient and sustainable, and Goal 13 – to take urgent action to combat climate change and its impacts.
The increase of population in cities associated with climate change can create innumerable environmental, economic and social problems, around the world. As it densifies, the demand of space for building and higher impermeabilization of surfaces occur, resulting in fragmentation of green areas, ecosystem degradation, loss of biodiversity, heat island effect, water, air and land pollution and consequently leading to deterioration of human wellbeing and disconnection to nature. Besides that, as a consequence of climate change, extreme events are also occurring more often such heavily rains, originating floods, and in the opposite, occurrence of droughts and heat waves.
Nature is back
Nature is being called back to the city not as a mere adornment but for its valuable services – ecosystem services. According to the Millennium Ecosystem Assessment (2005) “ecosystem services are the benefits people obtain from ecosystems”. They are grouped in four major categories as provisioning, regulating, cultural and ecosystem supporting services. Provisioning services refer to material products obtained from ecosystems such as food, water and fiber. Regulatory services refer to the benefits arising from the regulation of ecosystem processes, such as climate, water and air quality, and the spread of diseases. Cultural services comprise the non-material benefits, such as cognitive development, spiritual enrichment, including educational values, cultural diversity, aesthetic and cultural heritage values. Supporting services are those that are necessary for the production of all other ecosystem services, such as soil formation, photosynthesis, primary production, nutrient and water cycling. Therefore, the human being depends on nature to survive as a source of food, drinking water, clean air, climate regulation and other services. Ecosystem services are often ignored since we do not have to pay for them, which is why they are often easily discarded and sidelined when considering the implementation of urban infrastructures. Traditional infrastructure systems worldwide rely on built solutions (grey infrastructure) that is the usual choice made in detriment of green infrastructure, for example with regard to flood prevention. Often, the solutions presented within the scope of green infrastructures are less expensive than grey ones and provide a wide range of co-benefits for local economies and the environment. The integration of Nature-based solutions (NBS) as part of green infrastructures can provide multiple benefits to multiple stakeholders (Figure 1).
Figure 1 (source: Climate-KIC)
In many circumstances, combining green infrastructures with traditional grey infrastructures, can enhance the whole system performance, boost resilience, lower the costs, and better protect the communities. For example, the concept of “sponge city” relies on the purpose of improving water availability in urban settlements in order to retain urban runoff for eventual reuse, through a combination of NBS and grey infrastructures. The objective underpinning this strategy is to assure that most of the rain water is absorbed and reused through improved water permeation, retention and storage, purification and drainage, as well as water saving and reuse.
Green infrastructures and Nature-based solutions
European Union defines green infrastructure (GI) as “a strategically planned network of natural and semi-natural areas with other environmental features designed and managed to deliver a wide range of ecosystem services”. Nature-based solutions can integrate these GI as being “solutions that are inspired and supported by nature, which are cost-effective, simultaneously provide environmental, social and economic benefits and help build resilience“. Examples of NBS are rain gardens, bioswales, green roofs, green walls, tree trenches, swales, detention basins, wetlands and ponds. The green infrastructure acts as a structuring element of the urban landscape, intended to improve connectivity between territories, increase permeability and promote multifunctional areas, helping to maintain the services provided by ecosystems. In addition, it promotes adaptation to the effects of climate change and favors the mitigation of environmental impacts.
Four main goals have been identified by European Union that can be addressed by NBS:
i) Enhancing sustainable urbanization through NBS: it can foster economic growth and at the same time a better environment, making cities more attractive, and promoting human well-being.
ii) Restoring degraded ecosystems through the use of NBS: it can enhance ecosystem resilience, allowing them to provide vital ecosystem services and meet other societal challenges.
iii) Developing climate change adaptation and mitigation schemes through the use of NBS: it can provide more resilient responses and enhance the storage of carbon.
iv) Improving risk management and resilience through the use of NBS: it can lead to greater benefits than conventional methods and provide synergies in reducing multiple risks.
Bringing NBS to the city promotes urban regeneration, being the green roofs a good example that provide several environmental and social benefits, besides enhancing economic development (Figure 2). Resourceful and circular cities, with a strong nature-based component and having in consideration the built materials, will provide multifunctional and multipurpose spaces.
Figure 2: Green roof at Praça de Lisboa-Portugal
Potential components of green infrastructure
The physical elements that contribute to a green infrastructure can be considered at the local, regional or national scale. Therefore, are considered according to the European Union:
- protected areas (e.g. Natura 2000 sites);
- areas identified of high natural value, such as wetlands, coastal zones, floodplains and forests;
- natural passages for wildlife that can act as ecological corridors or stepping stones, that include natural landscape elements such as water courses, forest patches and hedgerows;
- zones of restored habitats that have been designed for certain species and to promote a certain function such as extending feeding zones, promoting mobility and geographic distribution, etc;
- elements designed as eco-ducts or eco-bridges, which were featured to allow species to circulate in the face of insurmountable obstacles and landscape barriers;
- multifunctional areas where the maintenance and regeneration of ecosystems is associated with consistent land use;
- areas that are the target of interventions to improve general ecological quality and landscape permeability;
- urban elements such as green parks, green walls and green roofs that promote and host biodiversity and associated services serving as a link between urban, peri-urban and rural areas;
- elements with adaptive function and mitigation to climate change, such as marshes, floodplain forestsand bogs. Preventing flood, acting as water storage and CO2 intake, providing space to species to react to change in climate conditions.
EU policies and green infrastructure
A European Union R&I agenda on NBS is an essential component to greening the economy and achieving sustainable development. Within the scope of the EU Biodiversity Strategy for 2020 the Commission’s commitment to prepare a strategy for green infrastructure was included, and in 2013 a document was issued in response to that commitment. However, there is a need for greater effort from the Member States to implement it. In 2015, the European Environment Agency issued a report that explores “nature-based solutions” through the role of green infrastructure, in its contribution to mitigating the adverse effects of extreme weather events and the impact of climate change. The importance of green infrastructures is therefore recognized by the domain of EU policies through some examples, such as: the 7th Environment Action Programme (EAP)- the Union’s General Program of Action for 2020 on the Environment “Living well, within the limits of our planet” (Decision No 1386/2013 / EU), EU Biodiversity Strategy for 2020: Our life insurance, our natural capital (COM (2011) 244 final), the European Commission’s Strategy on Green Infrastructure – Enhancing Europe’s Natural Capital (COM / 2013/0249 final), the Regional Policy 2014–2020, the Water Framework Directive, the Nitrates Directive (91/676 / EEC), the Floods Directive (2007/60 / EC) and the EU for Adaptation to Climate Change (COM (2013) 216). Green Infrastructure can play a fulcra role in integrating biodiversity into other policies, such as water, marine and fisheries, agriculture, forestry, regional and cohesion policy, climate change mitigation and adaptation, transport, energy and land use policy.
The way in which the occupation of the territory developed and the cities evolved, led to a disruption in natural flows. Cities have become more impermeable and with an increasing fragmentation of habitats and degradation of ecosystems. Green infrastructures operate at different scales and rely on nature to generate environmental (eg biodiversity conservation or adaptation to climate change), economic (eg job creation and property valuation) and social (eg water drainage) advantages and green spaces. In addition, it plays an important role in mitigating the effects of urbanization, aiming to strengthen urban ecosystems in order to be more resilient to the challenges of climate change and contributing to the transition to a low carbon economy.
The strategy for changing territories involves the conversion of mono-functional to multifunctional areas using green infrastructures with support or complemented by grey infrastructures. The use of nature-based solutions are important tools that follow the European Union’s alignment for the establishment of resilient cities.
The literacy of the citizens regarding the interpretation of the landscape is a central issue in the success of a new way of living and shaping spaces, in which the extermination of nature is not the answer, but rather to work with it. Otherwise, it will be a losing battle in detriment of our own quality of life.
Various contributions from green infrastructures are already established at different scales, such disaster risk management, environment and climate change, and it is now necessary for green infrastructure to become a popular element of planning and territory development.
To meet the ambitious goals of the 2030 Agenda and the Paris Agreement, we need to entail substantial global investments and an unprecedented transformation of the global infrastructure system.
Cristina Calheiros | CIIMAR | Environmental Engineer & Scientific Researcher