Riparian restoration

Planting zones before planting a site and where the likely floodplain would be. Image by Wellington City Council, Toitū te marae a Tāne restoration planting techniques guide.

Riparian zones are complex intermediary habitats of both terrestrial and semi-aquatic plants and animals that are located on the margins of water bodies. Riparian restoration planting occurs primarily in habitats that include streams, rivers, springs, lakes, floodplains, estuarine edges, and other natural or constructed hydrological ecosystems.

Riparian zones play a crucial role in providing essential ecosystem services. They act as natural filters for overland flow, effectively reducing sediment and pollutants entering water bodies. Additionally, these zones serve as vital shelters for aquatic life, creating critical habitats and regulating water temperatures, which is especially important for maintaining healthy aquatic ecosystems. Furthermore, riparian vegetation stabilises the edges of water bodies, preventing erosion and maintaining the integrity of riverbanks.

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Name of NbS

Riparian restoration

Type of NbS

Ecosystem restoration

Location

  • Urban
  • Periurban
  • Rura
Riparian restoration. Photo by Manaaki Whenua – Landcare Research.

Relationship to Indigenous knowledge

For many Indigenous communities in Te Moananui Oceania, rivers hold significant cultural and spiritual importance (Hikuroa et al., 2011). These water bodies are often seen as living entities and are integral to cultural identity and heritage. For example, in Aotearoa New Zealand, the Te Awa Tupua (Whanganui River Claims Settlement) Act 2017 recognised the Whanganui River as a legal person, acknowledging the river’s significance to Whanganui iwi (tribes). This legal recognition supports the integration of mātauranga Māori (Māori knowledge) knowledge and values in the river’s management and restoration.

Local and Indigenous communities in Te  Moananui Oceania have historically adapted to environmental changes and challenges, such as climate variability and natural disasters. This adaptability and resilience are embedded in knowledge systems and practices, which can provide valuable insights into how river restoration projects can be designed to withstand and adapt to changing environmental conditions.

Effective river restoration often requires collaborative management approaches that include the participation and leadership of Indigenous communities. Co-management frameworks, where Indigenous knowledge and Western scientific approaches are integrated, can lead to more successful and culturally appropriate restoration outcomes. This collaboration helps build mutual trust and respect between Indigenous and non-Indigenous stakeholders. Parson et al. (2021) note that a continued emphasis on restoring ecosystems or keystone species within a framework of ‘a historical perspective’ must also question whose historical perspective is being taken into account when river restoration goals, targets, and approaches are being set. They emphasise the need to consider whose cultural landscapes and waterscapes are valued when decisions are made about what is being restored and/or protected and how the restoration practices are being enacted.

Incorporating Indigenous perspectives in river restoration projects helps ensure that these cultural and spiritual values are respected and preserved, fostering a sense of stewardship.

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Climate change benefits
  • Biomass cover loss
  • Changes in rainfall
  • Flooding
  • Reduced water quality
  • Sea level rise
  • Soil erosion 
  • Reduced soil quality
  • Reduced freshwater

Riparian zones are pivotal in both climate change adaptation and mitigation strategies. The presence of vegetation along water bodies is instrumental in mitigating the impacts of extreme weather events, such as floods and erosion, thus contributing significantly to climate change adaptation efforts. Urban riparian planting can effectively store large volumes of water and regulate extreme air temperatures through the process of evapotranspiration (Haase, 2017). 

Vegetation within riparian areas serves as a crucial carbon sink, absorbing and storing carbon dioxide from the atmosphere, thereby aiding in the mitigation of climate change.

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Societal / socio-cultural benefits
  • Disaster risk reduction 
  • Water security
  • Waste management and sanitation

When floodplains receive adequate support through riparian planting along rivers and streams, these habitats offer significant ecosystem services to urban residents living near these landscapes. 

Riparian planting not only yields ecological benefits but also creates recreational and educational spaces. For instance, case studies such as Kopupaka Park demonstrate how traditional knowledge of original riparian planting can influence contemporary restoration efforts. By integrating traditional Māori practices and utilising a woven crib wall system, these restoration projects not only restore the ecological integrity of riparian zones but also honour Indigenous cultural heritage. This approach not only enhances biodiversity and ecological resilience but also fosters community engagement and connection with the natural environment.

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Ecological and biodiversity benefits
  • Disturbance prevention
  • Habitat provision
  • Purification

Riparian planting plays a pivotal role in habitat restoration and wildlife conservation when appropriate species are employed. Diverse vegetation along waterways significantly enhances biodiversity, offering food and shelter for wildlife across a range of wetland and perennial habitats (Haase, 2017). This habitat diversity fosters thriving ecosystems, promoting the formation of stable and diverse food webs crucial for in-stream biota. Furthermore, riparian vegetation regulates temperatures and provides essential habitat diversity for in-stream biota (McKergow et al., 2016). Through these mechanisms, riparian planting not only bolsters wildlife conservation but also enhances the ecological integrity of aquatic ecosystems.

The restoration of riparian vegetation along watercourse margins enhances the resilience of riverine systems by controlling erosion and preventing flooding (Kesstra, 2018). These vegetated buffers act as effective barriers to pollutants and sediments, safeguarding water quality and overall ecosystem health. Additionally, riparian planting contributes to soil erosion prevention and water and soil purification, further supporting the overall health of riparian ecosystems.

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Stream cross section showing edges, banks, and floodplain. Image by Wellington City Council, Toitū te marae a Tāne restoration planting techniques guide.

Technical requirements

Riparian planting thrives when native plants suited to the eco-zone are carefully selected. This process involves careful selection of plant species that align with site conditions and proper ground preparation before planting. Ongoing maintenance is crucial to prevent overgrowth in the riverine system and to mitigate the risk of exotic weeds outcompeting restoration efforts. Maintenance tasks may include regular monitoring, weed control, and occasional replanting to uphold the integrity of the riparian ecosystem.

Community engagement and stewardship programs may play a pivotal role in ensuring the long-term success of riparian planting initiatives. These programs cultivate a sense of responsibility among local residents, fostering active participation and support for the preservation and maintenance of riparian habitats.

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Issues and Barriers

Many riparian ecosystems reside on private land, making landowners primarily responsible for riparian planting restoration and ongoing management. However, this reliance on private landowners can sometimes hinder the effectiveness of nature-based solutions. The success of riparian planting initiatives hinges on the knowledge, willingness, and commitment of landowners to restore and maintain these ecosystems. Challenges may emerge due to varying levels of understanding about the importance of riparian vegetation, differing priorities among landowners, and potential conflicts with land use practices. Therefore, raising awareness, providing incentives, and offering support mechanisms for private landowners are essential for enhancing the effectiveness and sustainability of riparian planting projects.

Opportunities

Restoring riparian vegetation along waterways offers more than just immediate benefits; it holds the potential to address broader ecological and environmental concerns within river systems. By revitalising riparian zones, entire river ecosystems can be rejuvenated, creating interconnected habitats that sustain diverse flora and fauna populations. Furthermore, strategic selection and restoration of wetlands alongside riparian planting can maximise sediment filtration and enhance water quality. This integrated approach not only improves the effectiveness of riparian restoration but also contributes to broader ecosystem health and resilience.

Riparian restoration projects present opportunities for community engagement and capacity building. Involving local communities, Indigenous groups, and stakeholders fosters a sense of empowerment and stewardship. It could facilitates knowledge sharing, cultural revitalisation, and the promotion of traditional ecological wisdom. Additionally, riparian restoration initiatives can generate socio-economic benefits by creating recreational opportunities, supporting eco-tourism ventures, and enhancing aesthetic values along waterways.

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Financial case

Daigneault (2017) shows that riparian margin restoration can yield substantial net benefits, ranging from NZ $1.7 billion to $5.2 billion per year, depending on margin width and cost assumptions. The benefit-cost ratios span from 1.4 to 22.4. Importantly, the study underscores that these estimates do not fully capture the added value of biodiversity enhancement or improvements in stream ecosystem health, among other benefits. Despite this limitation, the benefits accruing from climate resilience and freshwater quality enhancement outweigh the implementation costs. This suggests that the economic case for riparian margin restoration is robust, with the potential for significant returns on investment.

References
  • Daigneault, A. J., Eppink, F. V., & Lee, W. G. (2017). A national riparian restoration programme in New Zealand: is it value for money? Journal of Environmental Management187, 166-177.
  • Haase, D. (2017). Urban wetlands and riparian forests as a nature-based solution for climate change adaptation in cities and their surroundings. In N. Kabisch et al (Ed.), Nature-based solutions to climate change adaptation in urban areas, theory and practice of urban sustainability transitions (pp. 111 – 122) DOI 10.1007/978-3-319-56091-5_7
  • Hikuroa, D., Slade, A., & Gravley, D. (2011). Implementing Māori indigenous knowledge (mātauranga) in a scientific paradigm: Restoring the mauri to Te Kete Poutama. MAI review, 3(1), 9.
  • Keesstra, S., Nunes, J., Novara, A., Finger, D., Avelar, D., Kalantari, Z., & Cerdà, A. (2018). The superior effect of nature-based solutions in land management for enhancing ecosystem services. Science of the Total Environment610, 997-1009.
  • McKergow, L.A., Matheson, F.E., & Quinn, J.M. (2016). Riparian management: a restoration tool for New Zealand streams. Ecological Management & Restoration17(3), 218-227.
  • Parsons, M., Fisher, K., Crease, R.P. (2021). Decolonising river restoration: Restoration as acts of healing and expression of Rangatiratanga. Decolonising Blue Spaces in the Anthropocene: Freshwater management in Aotearoa New Zealand, 359-417.

Further resources