Let nature do the job
The head of WWAP sheds light on the power of nature-based solutions for sustainable water management
The role of ecosystems and the concept and application of nature-based solutions (NBS) for sustainable water management is not new. Indeed, the use of natural processes to manage water spans millennia, but “nature-based solutions” terminology emerged only recently. NBS are increasingly recognized as important to address complex challenges in water management – water scarcity, quality and disaster risk reduction – and can be used to support development goals in multiple policy areas.
The next edition of the UN World Water Development Report (WWDR) 2018, entitled “Nature-based solutions for water” aims to show the importance of considering NBS (in parallel with alternative/classical approaches) more fully in water management policy and practice, to assist Member States in the implementation of the 2030 Agenda for Sustainable Development. The WWDR series are UN-Water reports produced by the UN World Water Assessment Programme of UNESCO in close cooperation with several UN-Water members and partners.
NBS use natural processes to contribute to improving the management of water. The defining feature of a nature-based solution is not whether an ecosystem being used is completely natural (or even pristine), but rather whether the natural processes can be proactively managed to achieve water management-related objectives.
For example: both natural and constructed wetlands can play an important role in increasing water storage, improving water quality and reducing disaster risk. They can act as natural barriers or retention areas, working as a natural “sponges” by trapping rainwater surface runoffs and by controlling land erosion.
Ecosystems provide natural (“green”) infrastructure that can perform similar functions to, and therefore partially substitute or augment, built (“grey”) infrastructure. Combing “green” and “grey” infrastructure effectively, for example, in the context of integrated flood and drought risk management in a river basin, can lead to cost savings compared to grey infrastructure solutions alone. In addition, green infrastructure provides additional functions and co-benefits that can directly improve the overall performance, such as improving water quality, recharging groundwater, providing habitat for fauna and generating jobs and additional revenues.
Nature-based solutions are becoming increasingly recognized as an important opportunity for addressing complex challenges in water management.
Achieving multiple purposes though nature-based solutions is exemplified by the ‘Sponge City’ project, recently initiated by the central Government of China to improve water availability and reduce water risks in urban settlements. The ‘Sponge City’ concept uses a combination of NBS and grey infrastructure to retain urban runoff for eventual reuse. Measures include the installation of green roofs, walls and permeable pavements, as well as the revitalization of degraded lakes and wetlands, which absorb excess rainwater, thus mitigating floods. Rain gardens and bio-retention swales collect runoff and remove pollutants. Some of this water is then released back to the environment and stored to ensure the availability of water for irrigation and other uses during water scarcity situations (Horn and Xu, 2017).
Despite several advantages of NBS for water resources, there are also many challenges to enable them to meet their full potential. The main obstacles revolve around the uncertainties of performance and cost-effectiveness, regulatory and legal constraints and limited access to information and guidance on design, implementation, monitoring and assessment.
NBS are widely claimed to be “cost-effective”. Indeed, there are many examples of where this is clearly the case, but this does not mean they are always cheap or that there will be a significant return on investment. The actual costs of NBS vary considerably according to scale, location, socio-economic boundary conditions and type of application. Financial incentives to adopt NBS, such as ‘payment for environmental services (PES) schemes’, can help improve the NBS business case and facilitate decision-making, but they remain highly under-utilized in practice. A more nuanced approach is needed that includes additional grey infrastructure in harmony with green infrastructure.
The UN World Water Development Report (WWDR) 2018 will be launched on World Water Day (22 March) in different locations around the world, including the global launch at the World Water Forum in Brasilia. WWDR 2018 highlights opportunities for nature-based solutions with caveats that they are not a panacea and need to be considered on a case-by-case basis de- pending on local conditions (environmen- tal, economic, and societal). The focus is on finding the correct balance and identifying opportunities to apply NBS more broadly – a key challenge to develop European water management more sustainably.