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Online Tool Visualizes Impacts of Sea Level Rise on Unique Coastal Pools and Fishponds of Hawai’i

Published on: 02/19/2020
Region(s) of Study: U.S. States and Territories / Hawaii
Primary Contact(s): david.kidwell@noaa.gov

An anchialine pool on the west coast of the Island of Hawaiʻi. Credit TNC.

The west coast of the island of Hawai’i supports a variety of land locked “anchialine pools”, wetlands, and fishponds that support numerous endangered and endemic species, as well as provide key ecosystem services to natural and human communities. These habitats have come under new stress due to sea level rise, as well as human development. An NCCOS-funded project, led by The Nature Conservancy (TNC), has developed an online tool called a “story map” to visualize current and future impacts of sea level rise on these unique and historic Hawaii habitats.

Diagram illustrating (a) current conditions and (b) future risks to anchialine pools due to sea level rise: (1) Pools may become connected to the ocean at higher sea levels, (2) Invasive fishes may disperse during high water levels, and (4) Groundwater may inundate cesspools. However, (3) new pools will emerge in low-lying areas as daily groundwater floods previously dry areas. Credit TNC.

The TNC models used to create the story map incorporate flood frequency, magnitude, as well as both ocean and groundwater elevations to predict when and where pool habitats will shift. The models show how risks of invasive fish introduction, septic tank/cesspool contamination, and changing development pressures that might alter pool habitats from now until year 2080.

Anchialine pools form in natural depressions in the lava and have a subterranean connection to the nearby ocean. As sea levels rise, groundwater is also pushed upwards, creating new anchialine pools at higher elevations and submerging lower pools during storm surge events or high tides. When these habitats are submerged, invasive fishes are introduced to the pools, while septic tank and cesspool contaminants also enter.

The tool is already being used to make coastal management decisions and to plan for the future. For example, a local community non-profit at Kiholo Bay (North Kona) is using the app to identify adaptation measures for private landowners and restoration priorities for anchialine pool management within their Board of Trustees and staff meetings, and the County of Hawaii is incorporating the insights from the maps into their update of the Hawaii County General Plan.

South Kohala Regional Management plans have also incorporated the study findings for prioritizing land suitable for conservation to enable landward migration of pools and specific pools that are compatible for restoration via invasive species removal. The tool informed the first restoration of an anchialine pool since 1990, and due to its utility the project is being expanded to cover the remainder of the big island of Hawai’i.

The models and online story map tool are products of the NCCOS Ecological Effects of Sea Level Rise project Sea-Level Rise Modeling as a Catalyst for Effective Ecological Management in West Hawai‘i.

The project is led by The Nature Conservancy (TNC) in Hawaii.

View the Sea Level Rise Effects on Groundwater-fed Anchialine Pools online story map.

For more information, contact David.Kidwell@noaa.gov.

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