Module 2: The links between nature-based solutions, green infrastructure and water security
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A look at some key terms and definitions, as well as the relationship to water security. Some considerations on both scope and scale of needed interventions.
Introduction
Water is the primary conduit by which climate change affects both man-made infrastructure, economic activity and human health and well-being. Consequently, there is a large overlap between NbS and issues of water management, water scarcity and water quality.
At the same time, significant investments are made on infrastructure that seeks to harness or control the natural water cycle, whether inside cities, upstream in the watershed, or at the coast. As climate variability increases, shortcomings in traditional ‘grey infrastructure’ are becoming apparent and the benefits of a mixed approach, one that combines green with grey, are becoming clearer.
This module explores these linkages, offering up working definitions of key terms (such as Nature-based Solutions and green infrastructure).
It also clarifies the scope of the on-ramp — including those important elements that are not addressed in detail — such as the contribution of NbS to coastal protection.
Finally, there is a discussion about the scale required for NbS to have a significant impact, and what is realistic to expect of the impact that can be achieved by investing in NbS.
Working definition of NbS
Nature-based Solutions
A widely used definition of Nature-based Solutions (or NbS) comes from IUCN, the International Union for Conservation of Nature:
“Nature-based solutions are actions to protect, sustainably manage and restore natural and modified ecosystems in ways that address societal challenges effectively and adaptively, to provide both human well-being and biodiversity benefits. They are underpinned by benefits that flow from healthy ecosystems and target major challenges like climate change, disaster risk reduction, food and water security, health and are critical to economic development” (IUCN, 2016)
The IUCN goes on to describe the characteristics of nature-based solutions:
“A nature-based solution uses the tools that nature already provides to address issues resulting from poor land or resource use, climate change or societal challenges. Solutions often enhance existing natural or man-made infrastructure and spur long-term economic, social and environmental benefits”.
What is the link between NbS and water security?
Given that water is the primary conduit by which climate change affects both man-made infrastructure, economic activity and human health and well-being, there is a large overlap between NbS and issues of water management, water scarcity and water quality. In short, between NbS and water security.
Of course, Nature-based solutions are being applied in a variety of fields and not all involve the water sector. However, for the remainder of this on-ramp we will be limiting our discussion of NbS to those that have a direct relation to water security.
Nature-based solutions that contribute to water security can still vary widely.
A recent publication for the UK’s Department for International Development (Cooper, 2020) identified, amongst others, the following:
- source water protection
- wetlands restoration, protection, and construction
- water harvesting
- agricultural best management practices
- soil conservation
- afforestation
- protecting mangroves
It suggests that these approaches and activities — in the right circumstances — can improve the timing, location and quality of water in both rural and urban settings.
Moreover the type of intervention can be quite different, sometimes looking to restore what was there before, on other occasions looking to create new natural systems, previously not existing in that location.
What is water security?
The Asian Development Bank says that societies can enjoy water security when:
“… they successfully manage their water resources and services to satisfy household water and sanitation needs in all communities; support productive economies in agriculture, industry, and energy; develop vibrant, liveable cities and towns; restore healthy rivers and ecosystems; and build resilient communities that can adapt to change” (ADB, 2013)
Yet there are many societies that fall short of this ideal — 25% of the world’s population now live in countries that face extremely high levels of baseline water stress (WRI, 2019).
Already, the World Business Council for Sustainable Development estimates that water shortages cost the global economy over US$323 billion annually. To put this into perspective, this is roughly double the value of the entire global wheat harvest (FAO, 2018).
To make the situation graver, higher water stress is predicted for our future.
By 2030, the number of large cities in the extremely high water stress category — with repercussions for public health and social unrest — is expected to rise to 45 and include nearly 470 million people.
Where does green infrastructure come into it?
In 2013 the European Union, in their white paper on Building a Green Infrastructure for Europe (EU, 2013) defined green infrastructure as follows:
“Green Infrastructure can be broadly defined as a strategically planned network of high quality natural and semi-natural areas with other environmental features, which is designed and managed to deliver a wide range of ecosystem services and protect biodiversity in both rural and urban settings. More specifically GI, being a spatial structure providing benefits from nature to people, aims to enhance nature’s ability to deliver multiple valuable ecosystem goods and services, such as clean air or water.”
The intention behind it is to combine different measures (such as reforestation, restoration of wetlands, permeable pavements in urban areas) in a strategic fashion in order to preserve, enhance or restore elements of a natural system.
A 2019 document from the World Bank outlines how such green infrastructure can be integrated with traditional grey approaches, to produce more resilient and lower cost solutions (Browder et al., 2019). A lot of the literature on green infrastructure is urban focused, but this approach can certainly be applied more widely, including to watersheds and whole water basins. The World Bank suggests three key opportunities that this offers, as outlined in the infographic below.
In addition to improving resilience, multiple benefits are often ascribed to green infrastructure approaches. Adherents are also keen to find ‘win-win’ opportunities that engage communities and provide new economic prospects for them. Finally, depending on the niche, the report argues that in the long-term, certain green infrastructure approaches can compete directly with traditional (grey) approaches in terms of cost alone.
In the realm of urban green infrastructure one example gaining in prominence is that of China’s ‘sponge cities’.
These work by harnessing green infrastructure to manage the hydrological pathways inside the city, in order to better regulate run-off as well as improve groundwater recharge. The first ‘sponge cities’ in China started to appear around 2013 to mitigate severe urban water-related problems (Wang et al., 2018). Combining green and grey infrastructure, the objective of this strategy is to reduce urban flooding and control urban water pollution. By filtering rainwater through various ‘green interventions’ the aim is to not only improve water quality, but also to reduce ecological degradation commonplace in urban water systems. A key benefit is to increase the resilience of cities even as urbanization grows, climate change sets in and natural disasters become both more severe and more frequent.
The type of green infrastructure being invested is diverse but includes: green roofs, vegetable swales, permeable pavements and bioremediation. Each is dependent on the other, and together the intention is that the system functions as a ‘sponge’, reducing peak flows and also removing some pollutants.
Scope of the on-ramp when dealing with NbS and green infrastructure
Although much of the literature, especially when it comes to green infrastructure, centres on interventions within the ‘urban envelope’, the scope of the on-ramp is wider than this.
Given our focus on the wider hydrological cycle — and some evidence suggesting that, to be effective, NbS interventions need to be applied at a significant scale — we seek to balance discussion between ‘inside-city’ activities and those that take place in peri-urban and rural areas. We further look to discuss approaches that can be implemented in both developing and developed countries, since a lot of the (English language) existing evidence base about urban interventions is sourced from Europe and North America.
That said, our focus is largely a terrestrial and freshwater one, in that we do not go into much detail about coastal engineering and its nature-based equivalents. This despite the fact that one area of much interest on NbS is in the performance of mangrove forests — or other natural coastal systems — in part as a defense against storm surges and other climate-related threats, acting either along and nearby coastlines.
Being realistic about the impact that can be achieved by investing in NbS — and the scale that such investments necessitate.
The evidence base for different NbS is varied and the scale at which certain interventions need to be applied clearly depends not only on the local context. but also on the level of ambition.
Taking wetlands as but one example, a meta-analysis of the flow regulation capabilities of wetlands found that on average, wetlands can reduce the frequency and magnitude of floods, increase the flood return period, augment low flows and decrease runoff and streamflow, but that there was substantial variation in the estimated effects between studies (Kadykalo & Findlay, 2016).
When looking at impacts across an entire watershed or water basin, it is clear that there can be trade-offs and, on occasion, global level benefits are juxtaposed with local level losses (for instance, increased flood risk in one location as a trade-off against improved flood resilience across a larger area).
Some go as far as arguing that interventions should operate at the same scale as the ecosystems themselves in order to achieve real impacts, including the recently published IUCN standards on NbS (IUCN, 2020).
Again, this can pose a challenge when considering watersheds. At the ecosystem scale, whether this be a river basin, flood plain, or other, hydrological and other natural boundaries will rarely overlap neatly and simply with other key boundaries, whether these be political, administrative or associated with land ownership.
Example: The Greater Cape Town Water Fund
The above video discusses the ‘business case’ that underpins the Greater Cape Town Water Fund in South Africa. One of the key advantages that exist there is that much of the land on which the alien vegetation has spread is not only owned by government, but is under the management of one specific government agency, Cape Nature.
The other point to note is that nature-based solutions are not being proposed for the entire catchment, but rather a scientific modelling process has led to a focus on only the most impactful sub-catchments. This increases the ‘return on investment’ in undertaking activities there — making the case for a ‘green infrastructure’ approach that much stronger.
Whereas for the Greater Cape Town Water Fund the scale of the intervention remains manageable — and the land in question is largely controlled by one or two key actors — other contexts are far more challenging.
A recent study commissioned by TNC on using NbS for groundwater recharge in Guatemala concluded that if NbS approaches were expanded to cover 10% of a key watershed (reversing some of the damage caused by land changes, including over-grazing and deforestation), the impact on groundwater recharge would only be in the region of 2.5 to 3.5%.
In conclusion then, the impact that NbS and green infrastructure can have is typically quite context-specific and for those seeking to implement them, it is healthy to acknowledge this fully from the outset.
Groupwork: Module 2
We recommend these activities be done in groups of between 2 and 6 people. If you are a larger group than that, then please consider splitting into two smaller sub-groups.
This group work mostly involves just talking to other members in the group, based on notes you make for yourself. Other group work involves templates that are shared there.
Step One
Discuss what problem you are trying to solve as a group using NbS.
Step Two
Discuss whether you envisage applying NbS inside the city, in the peri-urban areas touching the city perimeters or in rural areas. What problem are you trying to solve as a group using NbS? If you’re addressing water security, which are the top two interventions you may consider from: wetlands restoration/protection/construction; water harvesting; agricultural best management practices; soil conservation; reforestation or afforestation; or the protection of mangroves? Or do you have another one in mind altogether?
Step Three
As a group (you can all do this as individuals) listen to the following podcast, branching off the World Bank report on integrating green and grey infrastructure:
Discuss which parts of the podcast make you optimistic and which, if any, make it sound like there will be challenges ahead.
Quiz: Module 2
Questions
- Which global insurance giant recently stated that: “A fifth of countries globally are at risk of their ecosystems collapsing due to a decline in biodiversity and related beneficial services”?
- Water shortages already cost double the value of ? (Select an option)
- Which organisation suggested that “Green infrastructure … aims to enhance nature’s ability to deliver multiple valuable ecosystem goods and services, such as clean air or water”
- What percentage of world population will be at risk of flooding by 2050 (according to today’s trends)? (Select an option)
Sources
For the source material for all modules, including this one, go here:
Module 3— accessed via a link provided the end of the quiz survey above — addresses the following:
To see the overview of all modules, go here:
