What are nature-based solutions?
The European Union is committed to develop nature-based solutions, and supports various initiatives in this direction including research and innovation projects: “Nature-based solutions are innovations inspired and supported by nature, which are cost-effective, simultaneously provide environmental, social and economic benefits and help build resilience. They bring more, and more diverse, nature and natural features and processes into cities, landscapes and seascapes, through locally adapted, resource-efficient and systemic interventions. Nature-based solutions must benefit biodiversity and support the delivery of a range of ecosystem services.”
Nature-based solutions are supported in many different contexts, by very different actors in the world. Examples:
- The : “Nature-based solutions are actions to protect, sustainably manage, or restore natural ecosystems, that address societal challenges such as climate change, human health, food and water security, and disaster risk reduction effectively and adaptively, simultaneously providing human well-being and biodiversity benefits. For example, a common problem is the flooding in coastal areas that occurs as a result of storm surges and coastal erosion. This challenge, traditionally tackled with manmade (grey) infrastructure such as sea walls or dikes, coastal flooding, can also be addressed by actions that take advantage of ecosystem services such as tree planting.”
- The International Union for the Conservation of Nature (): “Nature-based solutions are actions to protect, sustainably manage, and restore natural and modified ecosystems that address societal challenges effectively and adaptively, simultaneously benefiting people and nature. Nature-based solutions address societal challenges through the protection, sustainable management and restoration of both natural and modified ecosystems, benefiting both biodiversity and human well-being. Nature-based solutions are underpinned by benefits that flow from healthy ecosystems. They target major challenges like climate change, disaster risk reduction, food and water security, biodiversity loss and human health, and are critical to sustainable economic development.”
Nature-based solutions for better water management
Nature-based solutions may be cost-effective in addressing water management issues in agriculture.
Treatment wetlands enable the removal of excess nutrients from manure in areas with limitations to fertilizers application. Reed beds may be a cheap and operationally simple option for the treatment of sludge, producing a compost that can be used to increase the organic matter content of soils. When treating domestic wastewater sludge with little runoff and industrial contributions, likely to contain low levels of metals and other persistent contaminants, the long retention time of reed beds ensures degradation of the less persistent chemicals, hence potentially a sludge of good chemical quality that could be a valuable soil conditioner. These solutions may be often financially self-sustainable.
Buffer strips and ponds are effective ways to control diffuse pollution. Their broad implementation may be cost-effective in reducing nutrient and pesticide loads to the receiving water bodies. However, they require public investments or anyway payments to farmers, as they represent net costs for them. Similarly, while ponds to store water for irrigation may be sustainable investments for farmers, their design oriented to support biodiversity entails extra costs that should be compensated in order to make them feasible. Similar considerations apply to in-stream retention measures such as two-stage design of drainage channels .
In some cases, there can be opportunities to restore valuable ecosystems while improving water management, although usually measures at the scale of the catchment require public support to trigger the investments needed to deliver the full benefits. An example of this is the restoration of Lake Karla as a multi-purpose reservoir. Finally, in other cases it may be possible to obtain significant benefits with relatively simple management changes, entailing limited costs, as suggested by the example of blocking the drainage of headwater streams in the Kyll river basin in Germany .
The implementation of NBS requires an assessment of costs and benefits in comparison with their “grey” alternatives, and the definition of appropriate “business models” to secure their broad uptake and sustainable operation.
Annexes to JRC Science for Policy Report
Potential to implement nature-based solutions in Europe
Here we address selected typologies of nature-based solutions (NBS), including:
- treatment wetlands for the removal of excess nutrients from manure and the stabilization of sludge;
- buffer strips, ponds and vegetated drainage ditches for diffuse pollution control;
- ponds for water storage and managed aquifer recharge to address irrigation demand.
We propose criteria to map the favourability to investments in the above NBS typologies for agricultural water management, their costs and effectiveness. We identify areas where each typology can be implemented, taking into account various constraints.
We introduce indicators representing the intensity of "demand" for NBS, i.e. presence of diffuse pollution loads, excess manure and sewage sludge, soil erosion and pesticide loads, summer deficit of precipitation with respect to potential evapotranspiration, lack of biodiversity at the landscape scale, and intensity of extreme precipitation requiring flood buffering.
Treatment wetlands (TW) are a well-established NBS for wastewater and sludge, particularly for the treatment of domestic effluents in small agglomerations or for the polishing of secondary wastewater treatment plant effluents. They are typically designed as free-surface water ponds or tanks, or tanks filled with gravel (“beds”) through which water may percolate and flow either horizontally or vertically.
Buffer strips and ponds
Control of pollution due to excess nutrients from agricultural fields, as well as other contaminants such as pesticides and suspended sediments, can be achieved through a series of diffuse elements, including buffer strips, vegetated drainage ditches and free surface wetland ponds, intercepting runoff before it is discharged to the receiving water bodies. This type of interventions becomes particularly effective when implemented systematically over a catchment, thus intercepting a significant percentage of the total runoff thereby produced.
Free water surface wetlands and vegetated drainage ditches operate the removal of nutrients and sediments by providing conditions for the settling of suspended solids, nutrient uptake by the aquatic vegetation, and denitrification by microorganisms in a complex ecosystem reproducing the conditions of natural wetlands. Buffer strips operate on the same principle, but through the uptake of nutrients by plant roots, entrapment of sediments and denitrification in soils. Buffer strips may be designed to intercept surface flow, subsurface or groundwater flow, or both.
Nature-based solutions for the collection and storage or retention of water can provide benefits in terms of water harvesting, flood mitigation or a combination of the two. Each aspect depends strictly on the volume of water available for these purposes. Depending on how the storage volumes are implemented, they may associate their hydrological function to an ecological, as well as a socioeconomic function. Among NBS for water storage we consider three strategies for water retention solutions that have a catchment-scale relevance: small farm-scale reservoirs in the form of ponds; large reservoirs restoring natural lake habitats; and restoration of the retention capacity of soils.
Maps and info tools
A research project led by JRC suggests an approach to using the above information to build scenarios of implementation of NBS, which can be applied for the appraisal of programmes of measures at the regional and European scale.
Annexes to JRC Technical Report
Usually NBS are designed on a case-by-case basis. It is very difficult to propose general design principles, and the economic, social and ecological benefits must be evaluated in the specific context. While guidance documents exist, it is often useful to take inspiration from available case studies. Here we present a few cases where NBS have been analysed in-depth in their technical, economic and social/ecological aspects.