Integrated valuation of a nature-based solution for water pollution control. Highlighting hidden benefits

Liquete, C., et al., 2016. Ecosystem Services

Original research (primary data)
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Abstract

In this study we assess multiple benefits (environmental, social and economic) provided by a multi-purpose green infrastructure (a series of constructed wetlands surrounded by a park) in a peri-urban area, and compare it with the alternative grey infrastructure and with the previous situation (a poplar plantation). We apply a multi-criteria analysis as a basis for integrated valuation. We address specific policy needs (strategic objectives) for the local territorial planning in the implementation of the EU Water Framework Directive. The analysis is used retrospectively (ex post evaluation) but our results could also be used prospectively to appraise new proposals of constructed wetlands under similar circumstances. The results reflect that the green infrastructure performs equal or even better than the grey infrastructure alternative for water purification and flood protection, it has a similar cost, and it provides additional benefits (like wildlife support and recreation). The most preferred alternative is the green infrastructure, followed by the grey infrastructure and the poplar plantation. This study demonstrates (a) the effectiveness of investments on nature-based solutions, (b) the potential of green infrastructures for delivering a broad range of ecosystem services, and (c) the utility of integrating different value systems and stakeholders’ viewpoints to support environmental decision-making.

Case studies

Basic information

  • Case ID: INT-183-2
  • Intervention type: Created habitats
  • Intervention description:

    INT 2 – Poplar plantation: private use of 4.2ha for productive forestry

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Freshwater flooding  No effect Water quality: Load reduction of dissolved organic carbon (t/yr), Load reduction of nitrogen (t/yr) Flooding: Peak flow reduction (%) return time of 10yr , Reduction of flooding downstream (m3) return time of 10yr
    Reduced water quality  No effect Water quality: Load reduction of dissolved organic carbon (t/yr), Load reduction of nitrogen (t/yr) Flooding: Peak flow reduction (%) return time of 10yr , Reduction of flooding downstream (m3) return time of 10yr
  • Approach implemented in the field: Yes
  • Specific location:

    Gorla Maggiore, a small municipality in northern Italy

  • Country: Italy
  • Habitat/Biome type: Created forest |
  • Issue specific term: Nature-based (general)

Evidence

  • Notes on intervention effectivness: Effectiveness determined by monitoring how the outcome measures change during a CSO event [Combined Sewer Overflow (CSO), i.e. the excess flow of mixed sewage and rainwater that cannot be treated in the waste-water treatment plant during heavy rain events] For INT 2, labeled as having no effect on water quality or flooding because was observed that CSO was directly discharged to the river before the construction of artificial wetlands [before construction was when the poplar plantation was the land-use]
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Another NbS plus other non-NbS approach(s)
  • Compare effectivness?: Yes
  • Compared to the non-NBS approach: Less effective
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: Yes
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: Landscape diversity: This is the Shannon's diversity index of the habitats
  • Assess outcomes of the intervention on people: Yes
  • Impacts for people: No-effect
  • People measures: Number of visits to the site as an indicator of Recreational/health benefits
  • Considers economic costs: Yes
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic:

Basic information

  • Case ID: INT-183-1
  • Intervention type: Created habitats
  • Intervention description:

    INT 1 - The present Gorla Maggiore water park, called here the green infrastructure. The water park is a constructed ecosystem of about 9 ha built on the Olona River bank during 2011–2012. It includes (a) a pollutant removal area composed of a grid, a sedimentation tank and four vertical sub-surface flow constructed wetlands; (b) a multipurpose area with a surface flow constructed wetland or pond with multiple roles, such as pollution retention (secondary and tertiary treatment), buffer tank for flood events, maintenance of biodiversity and recreational area; and (c) a recreational park with restored riparian trees, green open space, walking and cycling paths and some services (e.g. picnic table, toilets, bar) maintained by a voluntary association

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Freshwater flooding  Positive Water quality: Load reduction of dissolved organic carbon (t/yr), Load reduction of nitrogen (t/yr) Flooding: Peak flow reduction (%) return time of 10yr , Reduction of flooding downstream (m3) return time of 10yr
    Reduced water quality  Positive Water quality: Load reduction of dissolved organic carbon (t/yr), Load reduction of nitrogen (t/yr) Flooding: Peak flow reduction (%) return time of 10yr , Reduction of flooding downstream (m3) return time of 10yr
  • Approach implemented in the field: Yes
  • Specific location:

    Gorla Maggiore, a small municipality in northern Italy

  • Country: Italy
  • Habitat/Biome type: Created wetland |
  • Issue specific term: Nature-based (general)

Evidence

  • Notes on intervention effectivness: Effectiveness determined by monitoring how the outcome measures change during a CSO event [Combined Sewer Overflow (CSO), i.e. the excess flow of mixed sewage and rainwater that cannot be treated in the waste-water treatment plant during heavy rain events] For INT 1 “The free water sur- face constructed wetland works as a buffer tank to store 71% of the influent volume, with a less but not negligible role in lamination of vertical sub-surface flow beds (11%). Also the peak flow (86.2% of reduction) and the outflow duration (27.3 times higher than the CSO event duration) are satisfactorily managed during the 10 year return time events”
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Another NbS plus engineered approach(s)
  • Compare effectivness?: Yes
  • Compared to the non-NBS approach: More effective
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: Yes
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: Landscape diversity: This is the Shannon's diversity index of the habitats For INT 1 only -> biodiversity sampling of macroinvertebrates, macrophytes, birds, amphibians, pond vegetation + presence of threatened/priority species
  • Assess outcomes of the intervention on people: Yes
  • Impacts for people: Positive
  • People measures: Number of visits to the site as an indicator of Recreational/health benefits For INT 1 only: The level of appreciation of the users of the park [is between moderate and high]
  • Considers economic costs: Yes
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: Yes
  • Compared to an alternative: More costly

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic: