finding 27.2 : key-message-27-2

Pacific island ecosystems are notable for the high percentage of species found only in the region, and their biodiversity is both an important cultural resource for island people and a source of economic revenue through tourism (very high confidence). Terrestrial habitats and the goods and services they provide are threatened by rising temperatures (very likely, very high confidence), changes in rainfall (likely, medium confidence), increased storminess (likely, medium confidence), and land-use change (very likely, very high confidence). These changes promote the spread of invasive species (likely, low confidence) and reduce the ability of habitats to support protected species and sustain human communities (likely, medium confidence). Some species are expected to become extinct (likely, medium confidence) and others to decline to the point of requiring protection and costly management (likely, high confidence).

This finding is from chapter 27 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

To frame this chapter, the regional leads wanted to maximize inclusiveness and represent the key sectoral interests of communities and researchers. To select sectors and a full author team, the coordinating lead author and regional chapter lead author distributed an online Google survey from September to October 2016. The survey received 136 responses representing Hawaiʻi and all the U.S.-Affiliated Pacific Islands (USAPI) jurisdictions; respondents identified which of the National Climate Assessment (NCA) sectors they were most interested in learning about with respect to climate change in the Pacific Islands and suggested representative case studies.884675c9-3e31-483d-b6b9-fd53b99875ae The five top sectors were picked as the focus of the chapter, and a total of eight lead authors with expertise in those sectors were invited to join the regional team. To solicit additional participation from potential technical contributors across the region, two informational webinars spanning convenient time zones across the Pacific were held; 35 people joined in. The webinars outlined the NCA history and process, as well as past regional reports and ways to participate in this Fourth National Climate Assessment (NCA4).

A critical part of outlining the chapter and gathering literature published since the Third National Climate Assessment (NCA3)dd5b893d-4462-4bb3-9205-67b532919566 was done by inviting technical experts in the key sectors to participate in a half-day workshop led by each of the lead authors. A larger workshop centered on adaptation best practices was convened with participants from all sectors, as well as regional decision-makers. In all, 75 participants, including some virtual attendees, took part in the sectoral workshops on March 6 and 13, 2017. Finally, to include public concerns and interests, two town hall discussion events on March 6 and April 19, 2017, were held in Honolulu, Hawaiʻi, and Tumon, Guam, respectively. Approximately 100 participants attended the town halls. Throughout the refining of the Key Messages and narrative sections, authors met weekly both via conference calls and in person to discuss the chapter and carefully review evidence and findings. Technical contributors were given multiple opportunities to respond to and edit sections. The process was coordinated by the regional chapter lead and coordinating lead authors, as well as the Pacific Islands sustained assessment specialist.

Description of evidence base:

Projections of sea level rise have been made at both regional and local scales (see Traceable Account for Key Message 3). Based on these projections, the effects of sea level rise on coastal ecosystems have been evaluated for the Northwest Hawaiian Islands.8fd88741-58fd-4753-ae35-af3a2ed38915,cd76b4d4-a868-4324-abb1-3400e5f19618,ae901019-a648-4f5b-b572-1c3e4da60da2,e0d5406b-6d06-4ba7-9419-f44e1feeb5c8,eb2800b8-395d-44cf-90cd-2f9f3abcc9de,44466960-d3a9-4374-b1cf-893bb8a476f0 There has also been an assessment of the effects of climate change to many small islands across the Pacific Islands region.0b9752b8-62d7-40e2-becc-1f2877d2ac27 The effect of sea level rise (and global warming) on mangroves has also been evaluated.e0d5406b-6d06-4ba7-9419-f44e1feeb5c8,160c86ad-71ad-4ea3-bfc7-7ad79026b886,6b60f34d-c84f-4bdd-84a8-78ff37ea2b2e,3bffd087-0af7-47d7-8a00-a21f0fc63569

Forecasts of how climate change will affect rainfall and temperature in the main Hawaiian Islands have been based on both statistical and dynamical downscaling of global climate models (GCMs; see Traceable Account for Key Message 1). Statewide vulnerability models have been developed for nearly all species of native plantsc0eb08ae-6725-4e68-b99e-1f2cef382c25 and forest birds,f483b8cf-8401-40ec-9001-23466261d5fa showing substantial changes in the available habitat for many species. More detailed modeling within Hawaiʻi Volcanoes National Park has suggested that rare and listed plants being managed in Special Ecological Areas will experience climate changes that make the habitat in these areas unsuitable.5eac12ba-e664-4eb2-aa66-18d9067566d8

Effects of climate change on streamflow in Hawaiʻi will largely be driven by changes in rainfall, although geologic conditions affect the discharge of groundwater that provides base flow during dry weather.381cc925-f22b-46a5-8a36-3e99bbd52635 A regional watershed model from the windward side of Hawaiʻi Island suggested that control of an invasive tree with high water demand would somewhat mitigate decreases in streamflow that might be caused by a drier climate.e69ceccd-2c27-48f0-b3fe-46ce1b67f636 Finally, it has been suggested that ocean acidification will decrease the viability of the planktonic larvae of native Hawaiian stream fishes.0c523a5a-213e-491a-9dcf-0a2c7eb05d77

New information and remaining uncertainties:

The timing and magnitude of sea level rise are somewhat uncertain. There is greater uncertainty on how climate change will affect the complex patterns of precipitation over the high islands of Hawaiʻi. There is also high uncertainty about how plants will respond to changes in their habitats and the extent to which climate change will foster the spread of invasive species.

Assessment of confidence based on evidence:

It is very likely that air and water temperatures will increase and that sea level will rise (very high confidence). Research indicates that global mean sea level rise will exceed previous estimates and that, in the USAPI, sea level rise is likely to be higher than the global mean (likely, high confidence). As a result, it is likely that climate change will affect low-lying and coastal ecosystems in Hawaiʻi and other Pacific islands, with medium confidence in forecasts of the effects on these ecosystems.

There is low confidence as to how rainfall patterns will shift across the main Hawaiian Islands. It is considered likely that changes in rainfall will result in ecologic shifts expected to threaten some species. However, there is low confidence in specific ecologic forecasts because the direction and magnitude of rainfall changes are uncertain, and there is a lack of robust understanding of how species will respond to those changes. It seems as likely as not that the responses of terrestrial biomes and species to climate change will result in additional complexity in the management of rare and threatened species.

This finding was derived from scenario rcp_8_5

References :

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