Riparian Restoration
Riparian:
Develop ability to utilize hybrid-novel ecosystems - prioritizing species based on potential habitat alteration impact.
For the first part of the discussion, the riparian restoration group was offered six climate change-resilient restoration strategies. Regarding using hybrid/novel ecosystems and prioritizing species based on habitat alteration potential (rather than species origin), the group questioned which non-native species could still be beneficial. Some participants shared their experience removing non-natives and replacing them with ʻahuʻawa and pili. These species successfully held space, along with follow-up maintenance for 3-5 years–until a desired seed bank was established. Participants expressed interest in creating corridors of connectivity–to support the movement of riparian species – which would require invasive species removal and managing secondary invasions. Central questions to support the implementation of this strategy were around prioritization–what species and where. Ephemeral streams were noted to be more vulnerable to climate impacts than main streams, and there was a desire to establish floodplain buffer zones using flood/drought-tolerant species to reduce sedimentation. Methods would differ between dry and wet riparian regions, such as building vegetation in dry areas and removing it in wet ones. Varying water quality also requires consideration, and maintaining surface water flow for ecozone connectivity may involve using equipment to physically reshape the landscape based on the area's water and land history.
In the second part of the discussion, the group outlined five steps to better utilize hybrid/novel ecosystems and species with habitat-altering potential:
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Hydrology: There are existing tools that present historical streamflow over 10- and 50-year intervals, including for ephemeral streams. Additionally, historical flow data is available for some locations, such as at Limahuli Garden and Preserve. It is also important to understand the surrounding zone, such as soil types (which NRCS has classified broadly for Hawaiʻi) and soil movement. Conducting this type of synthesis will require complex coordination, with the Commission for Water Resources Management (CWRM) and the USGS Water Science Center indicated as key partners. Enhancing current hydrology tools by integrating climate and geomorphology data could inform restoration techniques. For example, floodplain design and step-pool structures, common in salmon restoration on the North American Continent, might be adapted–though Hawaiian streams may require different approaches due to big pulse events that might overwhelm built structures.
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Establish Desired Conditions: Restoration plans are evolving to include biodiversity and community use, meaning native and non-native plants might be considered for revegetation. Revisiting plans to incorporate community values is essential, with neighboring landowners and local communities as key partners. Invasive species removal and species additions will likely differ based on proactive versus reactive management.
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Species Profiles: Some species profiles that detail functional traits already exist, but there are information gaps, and some information is not easily accessible. Participants suggested some key traits, including shade and canopy coverage, growth rate, soil retention, nutrient inputs, and other ecosystem functions. A “Friend or Foe?” guide could help classify species based on their traits. Potential partners include Garden Smith and the Fish and Wildlife Service (FWS).
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Invasive Species Removal and Augmentation: Proactive and reactive management strategies will differ depending on the species and site-specific conditions. Developing detailed plans for this will be needed for effective restoration outcomes.
Restoration Handbook: There’s a need to consider substrate manipulation in riparian restoration. An NSF hui (team) at the University of Hawaiʻi at Mānoa and a NOAA project based on Maui to protect reefs may provide a good example resource.