The European Commission defines nature-based solutions as those which are inspired or supported by nature, are cost-effective, simultaneously provide environmental, social and economic benefits, and help build resilience (for example, to climate change).
Biodiversity loss caused by human-related pressures such as intensive agriculture, greater urbanisation and pollution has resulted in ecosystems being degraded across the EU. This affects the ability of nature to provide 'ecosystem services'. These services are generally public goods with no markets or prices; their degradation is therefore often not detected under the current economic system. Examples of ecosystem services include: water, air purification, fisheries, pollination, timber production and nutrient cycling.
In urban areas, nature-based solutions are increasingly being seen as the best way to restore and improve biodiversity - and therefore the ecosystem services it provides - and to enhance urban resilience.
Restoring urban biodiversity and connectivity
Restoring urban biodiversity and improving its ecosystem services is a major goal of several LIFE projects. For example, 'URBANCOWS' (LIFE10 NAT/EE/000107) is looking to improve the conservation status of coastal meadows and lagoon habitats in the Pärnu urban area of Estonia, thus improving coastal dynamics, water quality and retention. The project will clear reeds and bushes from 220 ha of coastal meadow habitat by reintroducing cow grazing on the land and restore the natural hydrology of 50 ha of coastal lagoons. Another project, 'URBANBEES' (LIFE08 NAT/F/000478), aimed to enhance the biodiversity of wild bees in urban habitats and therefore boost pollination services in urban areas. It created a total surface area of 883 m² dedicated to wild bees on its 16 urban sites in France, as well as establishing 2 000 m² of meadow in urban areas to support them.
Improving connectivity between natural sites and species populations across urban areas is an important component of maintaining and improving biodiversity. Several LIFE projects are focusing on this. For instance, 'Ljubljanica connects' (LIFE10 NAT/SI/000142) aims to improve the connectivity of fragmented fish populations in the Ljubljanica river and its corridor (upstream and downstream of the Ljubljana urban area). This is a vital habitat for numerous endangered species but one of the most degraded rivers in Slovenia. The project plans to remove barriers to fish migration, enhance and restore habitats, improve the water management infrastructure, and establish a water monitoring system.
'Life - OZON' (LIFE12 NAT/BE/000166) will link areas of high ecological value within Belgium's Sonian Forest, which covers parts of south-east Brussels, by constructing wildlife crossings, such as underpasses, viaducts and culverts. The forest is currently threaded by roads and railways, dividing wildlife populations and resulting in the deaths of over 50 roe deer and red foxes - the most common species - every year. The project should enable vulnerable species to move between isolated patches within the forest and extend the populations of typical species. Fences will also be erected to impede animals' access to roads and railway lines. It is hoped this will reduce road kill by 90%.
Around 40% of Zaragoza’s city area is significant in terms of biodiversity, but it suffers from isolation and fragmentation due to factors such as urban encroachment, degradation of river basins and deforestation. The 'LIFE ZARAGOZA NATURAL' project (LIFE12 ENV/ES/000567) aims to protect and improve biodiversity and connectivity in and between Natura 2000 network sites and other areas of natural interest within Zaragoza municipality. It is restoring the ecological status of several ecosystems such as rivers, riversides and wetlands, as well as focusing on forest and steppe areas. The restored areas will boost inter-connectivity and coherence of the municipality and will provide a multifunctional 'green' structure around the urban area. As part of the project, eight natural areas totalling around 5 ha will be partially or fully restored, with more than 1 000 new trees planted.
Green corridors and connectivity are also increasing in the Chanteloup loop, a peri-urban area near Paris, through the 'SeineCityPark' (LIFE11 ENV/FR/000746) project. This is being achieved through the use of natural clean-up techniques for tackling water and soil pollution and through the removal of invasive aquatic and terrestrial plant species. The improved connectivity will aid the free movement of land animals, birds, insects, amphibians and dragonflies across the urban territory. “We have managed to re-qualify whole areas and transform them into green corridors," explains project manager Isabelle Chatoux. "This has not only made our territory more resilient to flooding, but by making this ecological transition between park, the Seine and the city, we are protecting the environment and supporting the sustainable economic development of this area while improving the health and well-being of our citizens.”
Green infrastructure key
Green infrastructure is an important tool in urban areas; its underlying principle is that the same area of land can frequently offer multiple benefits and services if its ecosystems are in a healthy state. The Commission defines green infrastructure 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'.
Green roofs are an example of such infrastructure; they can help combat problems such as urban flooding and the heat island effect. A cluster of LIFE projects (GRACC, Roof Greening, GreenClimeAdapt) have demonstrated the benefits of green roofing since 1998. In particular, 'GreenClimeAdapt' (LIFE07 ENV/S/000908) tested green facades and roofs in Malmö. The project demonstrated an 8°C lowering of temperatures with green facades, 1-1.5°C lower indoor temperatures, reduced ground-level ozone readings near the green facades, and a higher biodiversity in their vicinity. A more recent project, 'LIFE Housing Landscapes' (LIFE12 ENV/UK/001133), is providing 2 790 m2 of enhanced green infrastructure within three high-density housing estates in West London. “We are expecting the measures to result in heat amelioration, reduced flood risk, improved air and water quality and sustainable drainage across the three estates,” says project manager Hannah Clay.
Rising temperatures can also be mitigated by the extension of forests in urban areas. 'EMoNFUr' (LIFE10 ENV/IT/000399) has clearly demonstrated this effect by monitoring urban and peri-urban forests in Lombardy, Italy, and the Osrednjeslovenska region of Slovenia. "By comparing the data obtained from the weather stations of the project with the data of 2002, we measured a decrease in temperatures," says project manager Enrico Calvo. "The cooling effect is greater at night (-0.7°C). This is very important as [for example] Milan in the last decades has undergone an average annual temperature increase of 1.5°C."
Enhancing blue infrastructure
Sealed surfaces tend to generate water runoff and urban flooding which can also affect the quality of surface waters. One way to counteract this phenomenon is by adopting blue infrastructure solutions. Since 2008, LIFE projects have focused on mitigating the effects of runoff water by adopting sustainable urban drainage systems (SUDS).
For example, the abovementioned LIFE Housing Landscapes is demonstrating sustainable urban drainage as part of a holistic package of blue measures that also includes rain gardens, drought-resilient plants and rainwater harvesting. Benefits will include a reduction in flooding risk, use of rainwater for garden irrigation and less wastewater to be treated. 'PLATAFORMA CENTRAL IBERUM' (LIFE11 ENV/ES/000538) is controlling the water cycle through rainwater harvesting and re-use, creation of permeable structures to avoid sealing, construction of canals and reservoirs to allow water to be collected for distribution, and the use of SUDS and the creation of storm ponds to maintain surface aquifers.
Open storm water management is another blue measure that can reduce the risk of flooding. It has been successfully demonstrated by the GreenClimeAdapt project in Sweden which built a catchment area capable of retaining 90% of the water of a 10-year rain event. Whereas in neighbouring Finland, the ongoing project 'Urban Oases' (LIFE11 ENV/FI/000911) is creating storm water swales in areas around Helsinki that are used to convey, infiltrate and clean storm water as well as to dissipate flow energy and store snow.
'LIFE-GREEN4GREY' (LIFE13 ENV/BE/000212) is focused on mitigating flooding in Flanders due to soil sealing. "We are implementing natural water retention measures such as re-naturalising artificial streams and creating wadis, which will have the effect of creating natural flooding areas and water retention bodies to capture water from rainfall during peak showers," explains project manager Pieter De Corte. Land use is also being changed from intensive agriculture to grasslands, increasing the soil's water infiltration capacity. In periods of heavy rainfall, these blue and green infrastructure elements capture water upstream.