One of the impacts of global climate change for the Hawaiian Islands is a projected increase in sea level of about one meter by the year 2100. This change will impact both biological and cultural resources located along the coastline. Few intact native coastal and lowland plant communities remain in Hawai’i. Many of those that remain contain listed endangered species and provide important habitat for other species such as seabirds, shorebirds, and native invertebrates. Where upslope habitats are available, some coastal plant communities may be able to migrate in response to sea level rise. However, in sites that have no upslope opportunities due to habitat modification by human development, the species and communities are vulnerable to loss. Similarly, many native Hawaiian cultural sites are found in coastal areas and are highly vulnerable to sea level rise since they are fixed in place. This project will use projections of sea‐level rise and coastal inundation to assess the vulnerability of native plant communities and associated cultural sites between now and 2100. The Pacific Islands Ecosystem Research Center has access to approximately 150 location records of coastal native vegetation from surveys conducted by Center personnel and other sources. Further surveys using the methodology described in Warshauer et al. (2009) will be conducted, as needed, to extend coverage under this project to the remaining areas of the coastline of the main Hawaiian Islands (excluding Ni’ihau) that still contain coastal plant communities. We will delineate and characterize these native shoreline plant communities with regard to species, diversity, disturbance, and other factors. Elevations of these plant communities will be derived from LiDAR‐based DEMS developed by the US Army Corps of Engineers and other sources. Exposure of the mapped communities to sea level rise will be derived from elevations and projected sea levels using passive inundation models modified where appropriate to approximate wave‐driven impacts. These modifications will be based on comparison of passive projections and available dynamic inundation models at representative locations. Sea level rise intervals will encompass the estimated range likely in the 21st century. Sea level rise and increased inundation from surf will also increasingly threaten native Hawaiian cultural sites. It is important for practitioners and other responsible parties to know which sites are most vulnerable so that strategies can be developed to mitigate these impacts. We will work with the State Historic Preservation Division to determine the location of cultural sites in delineated areas of native coastal vegetation to also assess how those sites may be impacted by changing sea level. An understanding of how sea level rise may affect remaining native plant communities will be needed to develop and implement adaptation measures. Roads, human communities or geology may act as barriers to natural shoreline retreat, and in those areas, active management or relocation efforts may be necessary. Using a landscape‐based vulnerability analysis framework, we will characterize the relative vulnerability of sites and species to sea level rise, determine the important proximate causes of vulnerability for each, and propose adaptation options.
