Fifth National Climate Assessment
30. Hawai'i and US-Affiliated Pacific Islands

Changing Climate Threatens Freshwater Resources

Dependable and safe freshwater resources and associated services in tropical islands are particularly vulnerable to rising temperatures (KM 4.1), altered rainfall patterns (Figure 30.3), runoff intensity and flooding, reduced groundwater recharge, and SLR (Figure 30.4; KM 4.2). Depletion of island aquifers compounds the potential for saltwater intrusion from SLR.^98,135,136 The availability of surface water for irrigation, drinking water, and hydropower is affected by increasing frequency and severity of flooding and by reductions in stream baseflow;¹³⁷ water contamination through increased Staphylococcus sp., Leptospira (a waterborne pathogenic bacteria), fecal coliform bacteria, and suspended sediment (KM 15.1);^{138,139,140,141} and extreme drought (KM 2.2).¹⁰³ In response to these changes, adaptation-focused restoration techniques are being applied, including revegetating with native species, reducing impervious surfaces, and redundant water distribution systems. Climate-induced land-cover change can have significant control over groundwater recharge, indicating that land-use adaptation is viable for managing impacts on water resources (KM 6.1).^142,143 Flood frequency is projected to increase across the region,⁷⁰ while drought frequency is projected to vary across the region (KMs 2.2, 4.1).^27,28,29,113

Changes Undermine the Sustainability of Water Supplies

Pacific Islands potable water supplies depend heavily on accessing clean groundwater or rain catchments, while other needs, such as irrigation, are often met with surface water resources. Groundwater recharge is affected by annual or longer-scale climate processes, while surface water supplies are more sensitive to shorter-term climatic influences.^{144,145,146,147,148} Although few studies assess regional changes in drought, evidence is clear that Hawaiʻi has experienced a drying trend since the 1950s and in La Niña years.^149,150 On atolls and low-lying islands, freshwater aquifers typically occur as very thin lenses and are highly sensitive to groundwater extraction and SLR-driven saltwater intrusion.^135,136 Shifting rainfall patterns and runoff conditions are affecting the availability of surface water to meet growing demands.¹⁰³ Climate change has elevated region-wide efforts to protect and conserve freshwater resources. Communities that rely heavily on rain-fed catchments and surface water are acutely susceptible to short-term and, in particular, long-term drought and the resulting reductions in streamflow.¹⁰³

Salinization and Pollutants Deteriorate Water Quality

Increased intensity of extreme rainfall events, coupled with SLR, is projected to exacerbate freshwater contamination risks.¹⁵¹ Past and ongoing disposal of military, industrial, agricultural, and municipal waste contaminates island water supplies.^35,152 Although SLR-driven mobilization of subsurface contaminants has received little study in the Pacific Islands, evidence of diverse groundwater contaminants in the region¹⁵³ and their mobilization^154,155 raises concerns for low-lying island aquifers (KM 4.2). Salt is a critical freshwater contaminant; wave-driven overwash^135,136,156 and SLR-induced rise of the freshwater–saltwater transition zone^{157,158,159,160} cause salinization and saltwater intrusion.

Changes in the frequency, severity, and duration of drought, associated fires, and flooding all interact to exacerbate sediment loading to streams.^103,161 Given the short ridge-to-reef distances in the region, sensitive nearshore coral ecosystems and fisheries are directly impacted by increased sediment and pollutant loads to streams,¹⁶² compromising biodiversity, subsistence practices, and economies (KM 9.2).^162,163,164

Food Systems Disrupted

Climate change will increasingly impact food production, transport, processing, packaging, storage, retail, consumption, and waste for Pacific Island communities (KMs 11.2, 13.1). The aforementioned challenges will disrupt imports reliant on fragile supply chains and reduce viability of local agriculture and fisheries, thus reducing access to nutritious foods.^{31,165,166,167,168,169} Fisheries are the principal protein sources for many Pacific Islanders, with locally grown staple food crops such as bananas, taro, breadfruit, and sweet potato supplying critical calories and nutrients.^170,171,172 However, Pacific Island communities have increasingly relied on imported foods, which come with complex and sometimes hidden environmental, financial, social, cultural, and nutritional costs (KM 30.2).^173,174 COVID-19 and previous disasters exposed the fragility of global supply chains (Focus on Risks to Supply Chains) and emphasized the need to bolster local food production capacity to increase resilience.^{166,167,175,176}

Declining Fisheries

The global capacity of coral reefs to supply fish has declined by half since the 1950s, a change that climate stressors have exacerbated (KM 9.2)^{62,177,178,179,180} through coral bleaching, acidification, SLR (Figure 30.4), terrestrial sediment, and contaminants (Box 30.3).^{78,79,181,182} Small-scale coral reef fisheries supply Pacific Island communities with a substantial portion (in some cases 50% to 90%) of their dietary protein and important micronutrients.^{82,172,177,183,184,185,186} Warming waters, acidification, and deoxygenation redistribute open-ocean fish stocks, and fisheries catch within regional EEZs is projected to decline by up to 40% by 2050 relative to the early 2000s under a very high scenario (RCP8.5; KM 10.1).¹⁰⁹ Fishing fleets are ill-equipped to adapt to this deficit (KM 10.2).^81,187 Warming, extreme events, acidification, and SLR may also compromise efforts to expand mariculture (marine farming), through damage to aquaculture systems,¹⁸⁸ decreased species richness,¹⁸⁹ and decreased local access to nearshore and open-ocean species.^190,191,192

Agriculture

Crop production in the USAPI has generally kept up with population growth over the past 20 years.^165,173 Although local agriculture provides a fraction of nutritional needs in the region,¹⁶⁵ it remains a critical food source, complementing imported foods, serving as an emergency food source, providing culturally important items, and supplementing household income and government revenue.^196,197

Climate change is projected to impact island food systems through a variety of different mechanisms (KMs 11.1, 23.3).⁷⁷ Warmer nighttime temperatures and saltwater intrusion, especially in FSM and RMI, are projected to increase damage from disease on staple crops such as taro, bananas, and breadfruit.^77,198 Cash crops are also likely to be affected, with higher temperatures and increased plant pathogens decreasing coffee yields, increased flooding depressing sugar yields, and higher winds damaging coconut palms, bananas, and breadfruit.¹⁹¹ In Hawaiʻi, droughts have become longer and more severe and are the principal cause of crop loss.⁴⁹

Adaptation Strategies to Improve Local Food System Resilience

Strategies are being developed and implemented across the region to revitalize healthier traditional food systems, resulting in more just access to food (KM 11.2).^{117,118,165,199} Subsistence-based food system practices such as agroforestry and fishing have sustained Pacific Island peoples for millennia and have aided in recoveries from natural disasters such as typhoons, earthquakes, volcanic eruptions, and tsunamis.^{119,171,200,201} Restoring Indigenous agroecology practices can support conservation, food security, and broader sociocultural objectives in the face of shifting precipitation and SLR (e.g., Bremer et al. 2018; Winter et al. 2020^202,203). Community food-sharing networks that empowered the most overburdened to overcome economic and social hardship during the COVID-19 pandemic offer a model for resilient food systems in the face of climate change.^175,204,205 Promising fisheries adaptations include establishing networks of marine protected areas to preserve coastal resources, safeguarding fish habitats from pollution runoff, and restoring traditional fishpond mariculture (KM 10.3; e.g., Bell et al. 2013; McLeod et al. 2019; Farmery et al. 2022^73,116,119).

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Climate change can degrade societal foundations of health and well-being, including access to shelter, nutritious food, clean water, and cultural and social relationships (KM 15.1). Prominent international frameworks and Pacific Island Indigenous conceptualizations of health and well-being recognize that the health of people is closely connected to the health of nonhuman beings, to the shared environment, and to place (Figure 16.3).^{209,210,211,212}

Indigenous communities of the Pacific Islands have actively responded to climate-related and other health risks, as well as external economic shocks (Box 30.3; KM 16.3).^119,205 However, colonization and economic disparities have resulted in disproportionately high rates of morbidity and mortality for Native Hawaiian and Indigenous Pacific Island peoples (KM 15.2).²¹³ Moreover, Pacific Island populations experienced severe economic shocks during the COVID-19 pandemic (KM 30.3),²¹⁴ which interacted with existing societal and non-climate stressors that worsen health inequities (KM 18.2).

The Health Impacts of Extreme Events

Tropical cyclone intensity,^53,215,216 drought frequency,^150,217 and flood potential (KMs 30.3, 2.2)^{70,98,218,219} are expected to increase and continue to aggravate social and geographic inequities (KMs 2.2, 4.2, 10.1, 16.1, 17.4).^53,98 Extreme weather impacts health in ways that persist beyond the initial disaster,^220,221 including increases in food- and waterborne pathogens, loss of access to medications and emergency services, loss of electricity needed for medical equipment and medical facilities, and disruptions to transportation networks, all of which increase illnesses and deaths (KM 15.1).²²² Healthcare facilities in the Pacific Islands are located primarily on coastlines, making them especially susceptible to tropical cyclones and SLR-driven flooding (KM 9.2),^104,223 with limited space and resources for relocation (KM 30.3).

The built environment is especially affected by extreme weather because of high costs of building materials, supply shortages, delays in code updates, and physical isolation (Figure 30.8; KM 30.3).²²⁴ Given the limited emergency infrastructure and evacuation options, extreme weather events create high risks for the mental and physical health of island populations, with individuals with low-income, older adults, children, and persons with disabilities at disproportionately higher risk (Box 15.1).^{26,225,226,227}

Drought poses health challenges, particularly for rural island populations. A 2013 drought in the northern atolls of RMI caused crop failures and unsafe and insufficient water supplies, which led to nutritional deficits and increased prevalence of infectious diseases, especially in children.^103,228 Severe wildfires, which occur primarily during droughts,^229,230,231 directly threaten health and safety and can create respiratory hazards (KM 14.2).²³²

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Extreme events acutely affect Pacific Island communities and their built environment.

Figure 30.8. In 2018 Super Typhoon Yutu struck the Commonwealth of the Northern Mariana Islands and damaged or destroyed a significant portion of the islands’ buildings and critical infrastructure, leaving a sizable population temporarily unhoused. The experience underscored how events such as cyclones, flooding, and droughts combine with societal factors to acutely affect human health and safety. Images show US Naval personnel clearing debris at a Tinian family’s home destroyed by Super Typhoon Yutu (top left); a satellite infrared image of Super Typhoon Yutu (top right); and a classroom in Hopwood Middle School on Saipan after the storm (bottom). Image credits: (top left) Matthew R. White, US Navy; (top right) NOAA/UWM-CIMSS, William Straka III; (bottom) Grace Simoneau, FEMA.

Health-Associated Impacts from Migration

Under a very high scenario (RCP8.5), human migration will increase due to SLR-driven inundation and salinization, displacing people, even entire populations, from low-lying atolls and low-elevation areas of high islands, with enormous implications for health and well-being (KMs 15.1, 17.1, 20.3).^98,105 Migrants often have difficulty navigating foreign healthcare systems²³³ and face other barriers to accessing healthcare, including ineligibility for federal programs.²³⁴ An improved understanding of the experiences and health outcomes of people who migrate, within or away from the USAPI, could inform better policy.

Mental Health Consequences and Climate Grief

Climate change directly and indirectly affects the mental health of Pacific Islanders.^235,236,237 On some islands globally, local climate stressors (such as floods, droughts, and SLR) are linked with negative mental health outcomes such as sadness, distress, and anger (KM 15.1).^238,239,240 Across the Pacific region, studies show that rural populations, socioeconomically disadvantaged groups, and people with disabilities experience more severe mental health consequences from various climate impacts (KM 15.2).^{105,239,240,241,242}

Research is limited on the mental health impacts of climate-induced migration. Instability caused by voluntary and involuntary migration is expected to be a continuing source of anxiety,⁹⁹ although evidence indicates that social cohesion and reducing disparities can counter negative impacts.^105,243 Some data show that distress from thinking about climate stressors can be comparable to that from experiencing direct impacts.²³⁹ Additionally, because Indigenous People in the Pacific are strongly connected to place, and place is central to conceptions of cultural identity, sudden ecological devastation or gradual change to the environment can create considerable stress (KMs 10.1, 15.1, 15.2, 23.1, 29.1).⁹⁹

Mental health services related to climate change show effectiveness when they are designed to serve Pacific Islander populations in a culturally centered way and include diverse ways of knowing.^235,243,244 Finally, the lack of studies on mental health and climate change in Hawaiʻi and the USAPI indicates that additional research may provide a more nuanced understanding of local implications. 

Increase in Vector-Borne Disease

Outbreaks of mosquito-borne diseases such as dengue, chikungunya, and Zika are increasing in frequency, extent, and duration across the region.^245,246 Changes in rainfall (Figure 30.3) and temperature, combined with environmental and demographic changes, are anticipated to exacerbate this trend.^34,247 Resources for vector control and managing outbreaks are limited on small tropical islands, and outbreaks sometimes overwhelm health systems.^245,247 Health officials in FSM, RMI, and Palau are developing predictive modeling to create a dengue early warning system.²⁴⁸ Similar to how chikungunya and Zika recently emerged and expanded in the Pacific, other vector-borne diseases may emerge in the future.²⁴⁹

High Temperatures and Heat-Related Illness and Death

As in much of the US (Figure 2.11), the number of hot days has increased across the Pacific Islands; 2020 was the region’s hottest year on record.^{27,28,29,45,113} A community heat assessment in Oʻahu, Hawaiʻi, in August 2019 found many neighborhoods with record-high afternoon heat indices between 100°F (38°C) and 107°F (42°C) (Figure 30.9).^250,251

Climate change–driven hot weather causes heat-related illness and increases hospitalizations and deaths; 82% of heat-related deaths in Honolulu are already attributable to climate change (KM 15.1).²⁵² Those more likely to experience heat-related illness include young children, older adults, outdoor workers, economically burdened and disadvantaged people with little access to cooling or healthcare (KM 15.1), military personnel whose duties require heavy gear and vigorous activity, and non-acclimated visitors.⁹¹ Shock events interact with heat: for example, after the 2009 tsunami in American Sāmoa, dehydration, heat stress illnesses, and barriers to receiving medical care increased.²⁵³

Imported low-quality foods have replaced local, nutritious, traditional diets (KM 30.1), resulting in some of world’s highest prevalence of noncommunicable diseases (NCDs).^{165,190,199,254,255} Heat worsens health outcomes for people with NCDs such as heart disease, cancer, stroke, and diabetes²⁵⁶ and creates challenges for the management of obesity and other diseases because exercise is more difficult to do safely. Overweight and obesity in young children are at a higher prevalence in American Sāmoa, CNMI, and Guam than globally.²⁵⁷

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High temperatures are responsible for heat-related illnesses, hospitalizations, and death.

Figure 30.9. This community heat assessment map shows the afternoon heat index and “hotspots” for the island of Oʻahu, Hawaiʻi. The inset is urban Honolulu. Data were collected by community volunteers and the City and County of Honolulu on August 31, 2019. On this day, the high temperature tied the hottest-ever recorded for Honolulu. Multiple neighborhoods on Oʻahu experienced afternoon heat indices above 100°F (38°C), with a maximum recorded heat index of 107.3°F (42°C). Climate change is increasing the frequency, intensity, and duration of heat extremes, putting individuals and communities at risk. Figure credit: Arizona State University, University of Hawaiʻi at Mānoa, NOAA NCEI, and CISESS NC.

Social Adaptive Capacity and Community Resilience

The ability of individuals, communities, and institutions to endure stress and adapt to change determines health impacts of climate change. Recent examples demonstrating the importance of social capital (such as community networks, equitable access to education [KM 15.3], sharing, and relationships) in disaster response include community initiatives addressing flooding on the island of Kauaʻi²⁵⁸ and drought in RMI.²⁵⁹ Traditional Knowledge and coping strategies can enhance adaptive capacity and disaster response in some contexts.^{260,261,262,263} The resilience of organizations, including health-related institutions and disaster response systems, depends on the ability of organizations to form relationships and communicate with one another, participation by traditional leaders and faith organizations, and effective planning by disaster management agencies (KMs 16.2, 20.2).^{227,264,265,266,267} Prioritizing social and mental health initiatives in the health sector would aid in responding to the psychological issues that emerge with disasters and climate change.²⁶⁸

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Built Environment

The built environment refers to all human-made structures, including buildings, transportation infrastructure (ports, airports, roads, and bridges), military installations, and distribution systems for food, water, wastewater, communications, and power (electrical, oil, and gas). For this region, it includes traditional structures such as burial grounds, fishponds, and taro terraces (KM 30.5). These structures are critical to connecting people and providing access to goods and services, yet their location within a few feet of sea level renders them particularly vulnerable to SLR (Figure 30.4) and natural disasters (KM 9.2). For example, 98% of RMI’s and 80% of Palau’s built infrastructure is located within approximately 1,600 feet of their coastlines.⁸⁵

Impacts to Infrastructure

Sea level rise will increasingly impact coastal infrastructure through increased magnitude and duration of storm wave–induced flooding (KMs 2.2, 9.1),^98,219,269 rising high tides,²⁷⁰ and increased coastal erosion (Figure 30.10).²⁷¹ In Hawaiʻi, 3.2 feet of SLR above 2000 levels, which could occur as soon as 2100 under the Intermediate SLR scenario or 2070 under the High scenario (for information on the likelihood of these scenarios, see Appendix 3; Figure 30.4),⁶⁵ would affect 550 cultural sites, 38 miles (6%) of major coastal roads, 6,500 structures, and 25,800 acres of land, potentially displacing 20,000 residents and incurring $23.1 billion (in 2022 dollars) in economic loss.⁹² Approximately 3 feet of SLR is projected to affect at least 58% of Guam’s built environment⁹⁰ and most atolls in FSM and RMI.⁹⁸ Highly urbanized atolls may not be able to adapt to future SLR (KMs 9.2, 12.2),^106,107 leading to land loss and potential uninhabitability.^98,108 Elevated SSTs can increase bleaching and degradation of coral reefs, which are some islands’ primary natural defenses (Figure 30.11; KM 30.4) against coastal flooding.²⁷² Lastly, increased flooding and erosion due to SLR and stronger future cyclones threaten US military bases in the region, potentially destabilizing regional security and the ability of the Department of Defense to respond to natural disasters (KM 17.1).⁵³

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Sea level rise is increasingly impacting infrastructure and communities.

Figure 30.10. Rising sea levels are increasing the frequency and magnitude of coastal flooding events. (top left) Cars travel through king tide flooding on Oʻahu, Hawaiʻi, in August 2019. (top right) High tide inundates a low-lying coastal area in Majuro, Marshall Islands, in February 2020. (bottom left) A residence on Oʻahu, Hawaiʻi, has collapsed due to coastal erosion during a large wave event in February 2022. (bottom right) American Sāmoa experienced flooding around homes in May 2021. Photo credits: (top left) Maya Walton via © Hawaiʻi Sea Grant King Tides Project, 2019 [CC BY 4.0]; (top right) Max Sudnovsky via © Hawaiʻi Sea Grant King Tides Project, 2020 [CC BY 4.0]; (bottom left) © Shellie Habel; (bottom right) Kelley Anderson Tagarino via © Hawaiʻi Sea Grant King Tides Project, 2021 [CC BY 4.0].

Art × Climate

J. Matt
Structure Failure on O‘ahu in the Global Warming Era
(2022, photography)

Artist’s statement: The Ke Nui structure failure illustrates the complexity of coastal climate politics. The owners are native Hawaiians who have kept the building in the family for five generations — descendants of a thriving kingdom overthrown under threat of U.S. arms. Receding coastlines will force reckoning with not only issues of historical Indigenous exploitations and wealth concentration but also community, individual, and states’ rights pertaining to physically indefensible coastal private property. Without a coastal action plan, property owners in Hawai‘i rely on illegal courses of action when responding to catastrophes such as this one.

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Artworks and artists’ statements are not official Assessment products.

Adapting the Built Environment

Protecting coastal infrastructure on small islands is costly and requires strong governance and thoughtful urban planning.²⁷³ Hawaiʻi has enacted forward-looking state and county policies, including increased minimum setbacks for coastal development,^274,275,276 setbacks incorporating science-based erosion rates and long-planning horizons that account for future SLR,^{275,277,278,279} a first-in-the-Nation mandate to disclose SLR hazards prior to real estate transactions,²⁸⁰ a requirement for state agencies to assess and plan for SLR impacts,²⁸¹ and a mandate that environmental impact assessments consider SLR and other climate factors.²⁸² While evaluating a balance between public and private property interests (KM 30.5), Hawaiʻi is also assessing the feasibility of relocating some coastal developments,²⁸³ prohibiting most coastal hardening,²⁷⁴ and helping to preserve public beach access.²⁸³

Nature-based solutions such as coral reef restoration^284,285 have been proposed at the federal (DARPA Reefense Program),²⁸⁶ state (e.g., State of Hawaiʻi 2021²⁸⁷), and territorial²⁸⁸ levels. Such solutions are potentially cost effective for protecting coastal infrastructure²⁸⁹ and habitats, sustaining ecosystem services such as fisheries (KM 30.1), and supporting tourism and recreation.²⁹⁰

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Coral reef degradation could affect thousands of people and cause millions of dollars in damages.

Figure 30.11. The maps show coastal flood protection that the top-most 3.28 feet (1 m) of coral reefs provide annually in American Sāmoa; Guam; Saipan and Tinian (Commonwealth of the Northern Mariana Islands); and Hawaiʻi. The maps display (a) the number of people per mile at risk and (b) the potential economic losses (in millions of dollars per mile) from direct building damages and indirect economic disruption from flooding. Adapted from Storlazzi et al. 2019.²⁹¹

Livelihoods and Economy

Demographics and Migration

Compared to Hawaiʻi, the USAPI have smaller populations and smaller land masses, as well as fewer financial resources, making adaptation more challenging. During 2010–2020, populations increased in Hawaiʻi and decreased in American Sāmoa, CNMI, Guam, and Palau.^{16,17,18,19,20,21} Pacific Islanders are moving from rural to more urban areas that sometimes lack resources and infrastructure to accommodate influxes of people.^273,292 Migration is a traditional strategy for coping with resource scarcity in Micronesia—for example, a family member often migrates to an urban area for employment, sending money home to support family needs.²⁹³ In 2020, these external remittances accounted for 5.7% of FSM’s GDP, 0.08% of Palau’s GDP, and 12.7% of RMI’s GDP.^294,295,296 As livelihoods in climate-sensitive sectors are impacted by climate change, the amount of money migrants send to relatives will be affected. Climate change may displace populations,²⁹⁷ but the extent to which climate change drives migration is not well established because migration is an inherent part of Pacific Island cultures.²⁹⁸ However, some evidence points to a strong correlation between climate impacts on ecosystem services (e.g., food and water provision, protection against floods and storms) and people’s propensity to migrate.²⁹⁹

Economy

The costs of adapting to, mitigating, and suffering the consequences of climate change are projected to increase over time, amounting to between 3% and 13% (under the 450ppm and SRES [Special Report on Emission Scenarios] A1FI scenarios, respectively) of Pacific Island regional GDP by 2100 (KM 19.1).³⁰⁰ Relative to Hawaiʻi and larger countries, USAPI economies have smaller total GDPs and GDP-per-capita and higher dependence on fisheries and agriculture—climate-sensitive industries representing a large portion of GDP.³⁰¹ They also are more dependent on remittances, federal aid, and foreign aid (KM 17.1).^302,303

Tourism is a major economic engine in the Pacific.³⁰⁴ Before COVID-19, tourism accounted for over 80% of total exports for Palau and less than 20% for RMI³⁰⁵ and approximately 25% of total GDP in Hawaiʻi. Climate change impacts tourism-based jobs and revenue. Damages to the built environment, especially coastal infrastructure, deterioration of natural assets, and expanding vector-borne disease occurrence could reduce tourism.³⁰⁰

Fishing is a critical economic sector in many Pacific Islands.^178,306 Tuna license revenues represent a significant source of government income for the FAS but are expected to decline due to projected changes in fish availability in the EEZs (KMs 10.1, 10.2),^{79,80,81,83,306} with ramifications for local canneries in American Sāmoa and the FAS. Changing coastlines and potential land loss from SLR may result in changed maritime entitlements via changes in the size and shape of the respective EEZs,³⁰⁶ affecting not just fisheries but also marine mineral rights. Climate-related marine and coastal habitat impacts threaten artisanal fisheries, a critical source of food and income for many households (KMs 30.1, 10.1, 10.2).^{78,82,178,184}

Estimated Economic Costs of Climate Change

The estimated economic impacts of climate change will vary by sector. Coastal hazards have a disproportionately large impact on small islands’ GDPs.³⁰⁷ Specifically, the projected increased duration and magnitude of storm wave–induced flooding^98,219,269 and increased coastal erosion²⁷¹ can damage infrastructure underpinning the local economy. Degradation of coral reefs due to a rise in SSTs²⁷² could incur coastal damages costing approximately $1.2 billion (in 2022 dollars) annually to the economies of Hawaiʻi and the US Pacific territories.²¹⁸

In American Sāmoa and Guam, coastal flooding and erosion are projected to disproportionately harm at-risk individuals, including minority and low-income populations and those younger than 16 or older than 65 (groups defined by the 2010 US Census data).²¹⁸ High-risk coastal properties (i.e., those located in hazard-erosion areas of updated FEMA Flood Insurance Rate Maps) will be difficult to insure.³⁰⁸ Increased coastal flooding events and drought are expected to negatively impact agricultural revenues (KM 30.1). For example, between 2008 and 2016, Hawai‘i lost approximately $53.5 million (in 2022 dollars) in cattle production due to the most severe drought on record, and federal crop insurance programs paid $11.2 million (in 2022 dollars) to farmers for drought losses during 1996–2018, mainly for macadamia nuts and coffee.⁴⁹

Adapting Livelihoods and Economies

As a percentage of GDP, the costs of climate change adaptation are significantly higher for small islands than for larger countries.^300,309 Islands’ geographic isolation, reliance on imported goods, and vulnerable infrastructure can increase adaptation and disaster recovery costs (see Figure 30.8).²²⁴ Hawaiʻi and the USAPI have adopted the United Nations Sustainable Development Goals (Box 30.2)¹³⁰ to increase resilience by creating more equitable approaches to adaptation and mitigation. Financing costly climate adaptation is a shared international challenge for the FAS (KM 17.4).^300,301 Unlike American Sāmoa, CNMI, Guam, and Hawaiʻi, the sovereign FAS are eligible for foreign direct investment and receive substantial funding from the Green Climate Fund,³¹⁰ the Asian Development Bank,^311,312 the US Government via the Compact of Free Association,^310,313 and other nations (KMs 19.2, 19.3).³¹⁴ Because credit agencies are increasingly considering vulnerability to climate change as a factor in their ratings, however, Palau’s and RMI’s credit ratings may decrease, with negative impacts on their abilities to borrow external funds, attract foreign investment, or access below-market-rate financing to accelerate development.³¹⁵

Decarbonization, Sequestration, and Resilience

Although many Pacific Islands emit minimal greenhouse gases, they are striving to reduce emissions and sequester carbon while addressing ecosystem resilience needs.¹¹⁹ For example, Guam and Hawaiʻi established 100% renewable portfolio standards for the electricity sector, to be achieved by no later than 2045.^316,317 Hawaiʻi established a net-negative emissions target by 2045 and created a sequestration task force²⁸² charged with establishing baselines and benchmarks, recommending policies including mitigation, and developing strategies for sustainable agriculture. This work led to a carbon pricing evaluation.³¹⁸ Similarly, RMI pledged emissions reductions of 45% below 2010 levels by 2030 and carbon neutrality by 2050.³¹⁹ Palau recently committed to 100% energy generation from renewable sources by 2032.³²⁰ Opportunities exist for ecosystem-based, place-based adaptation and mitigation informed by Indigenous Knowledge systems (KMs 30.1, 30.5).^321,322,323

With limited land areas, each island in the region is carefully evaluating options for transitioning to renewable energy. In 2016, American Sāmoa’s island of Taʻū transitioned its energy supply from 100% diesel to 100% solar with battery backup.³²⁴ In Hawaiʻi, rapid growth of rooftop solar generation—combined with centralized solar, battery storage, wind power, and pumped hydropower storage—is enabling a transition away from an oil-predominant grid.³²⁵ The potential for success is high: Kauaʻi’s grid achieved a 69.5% renewable portfolio standard in 2021, and the island is occasionally 100% renewably powered during midday hours; it is projected to achieve a 90% renewable portfolio by 2026.^326,327 Hawaiʻi’s Act 100³²⁸ required a community-based renewable energy program; power utilities and communities in the region are now developing mechanisms to enable shared ownership of renewable infrastructure.³²⁹

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Marine and Coastal Ecosystems

Pacific Island marine environments serve as the foundation for local food systems and cultures (Figure 30.12). Rising ocean temperatures, declining dissolved oxygen concentrations, and marine heatwaves are projected to impact the structure and composition of marine ecosystems (Figure 30.5; Ch. 8; KM 10.1).³³⁰ Global marine food web models project biomass declines of 10% to 40% across the region throughout this century, with greater declines projected for large predators.³³¹ Finally, marine species within the region’s EEZs are projected to shift beyond historical ranges as early as 2030—sooner than much of the globe.⁸³

Coastal and oceanic environments supply direct goods and services such as fish, recreation and tourism areas, regulating services such as coastal protection and carbon storage, and means for trade and transportation—collectively valued at over $3.1 trillion per year (in 2022 dollars; KM 23.2).³³² Rising SSTs and marine heatwaves continue to be the most pressing climate change impacts facing Pacific reefs,^333,334 leading to more frequent and severe bleaching events with less recovery time.^{61,62,335,336} Bleaching-induced mortality has reduced coral cover and decreased available habitat for reef-associated species.^62,334 Increased SSTs will negatively affect some animal species distributions,^337,338,339 and rising ocean and sand temperatures lead to a higher ratio of female sea turtles observed around the Pacific, threatening the viability of sea turtle populations.³⁴⁰ Increased air temperatures and reduced precipitation are likely to have negative effects on coastal vegetation³⁴¹ and coastal pond communities,³⁴² adversely affecting coral reefs, seagrasses, and mangroves via altered sediment and pollutant delivery to coasts.³⁴³ Increased ocean acidity³⁴⁴ and increased nutrient runoff from the land³⁴⁵ negatively impact corals, shellfish, and associated fisheries (KM 30.1). Although these systems generally have limited capacity to adapt to large climatic changes, regional strategies are being developed to reduce impacts.^337,338,346

Art × Climate

Constance Collins
Coral Conundrum: Dead or Alive
(2023, handmade paper, upcycled warp yarn remnants)

Artist’s statement: Coral reefs are being threatened globally from climate change, unsustainable fishing, and land-based pollution. This piece recalls coral reefs and their inhabitants. As reefs deteriorate, they lose their vibrant color and their ability to provide nutrients and shelter to thousands of marine species. Here, the gradation from color to monochrome represents the bleaching that occurs as coral dies. We need to protect these crucial ecosystems, or we lose them. I used upcycled remnant warp yarns for the coral clusters and created handmade paper.

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Sea level rise will cause more frequent and extensive flooding of coastal ecosystems, impacting plants^354,355 and animals,³⁵⁶ especially on low-lying atolls such as those in the Northwestern Hawaiian Islands, PRI, RMI, and FSM. In some cases, flooding is likely to increase erosion rates, reducing the elevation of mangroves, vegetated dunes, and beaches. Development exacerbates these drivers by exposing soils, creating impervious surfaces, and impeding inland migration of coastal ecosystems, limiting their adaptive capacity.³⁵⁷

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Pacific Island marine environments provide the foundation for local food systems and cultures.

Figure 30.12. Pacific Islands offer a diversity of ecosystems that include mangroves (top left), limestone forests (bottom left), tropical alpine habitats (top center), dry forests (bottom center), coral reefs (top right), and cloud forests (bottom right). Photo credits: (top left) Richard Mackenzie, USDA Forest Service; (top center) © Paul Krushelnycky, University of Hawaiʻi; (top right) © Underwater Earth / XL Catlin Seaview Survey / Christophe Bailhache; (bottom left) Christian Giardina, USDA Forest Service; (bottom center) Hawaiʻi Department of Land and Natural Resources; (bottom right) Lucas Fortini, USGS.

High Island Ecosystems

Terrestrial ecosystems of high islands (i.e., islands characterized by volcanic origin and consequently more diverse topography) have evolved in isolation from continental areas, resulting in unique and diverse fauna and flora with a high proportion of native species naturally occurring only on these islands (Figure 30.12). However, the combination of invasive plants and animals and diseases; habitat destruction; and intensifying fire regimes and ecological drought has resulted in severe range contractions and native species extinctions.^{93,358,359,360,361,362,363}

In Hawaiʻi, past droughts and rainfall variability had landscape-level impacts on vegetation^364,365 and cascading ecological effects.³⁶⁶ Long-term climatic shifts are likely to accelerate range contraction and extinction rates,^93,367 but responses will vary by species, including differences in drought tolerance across populations.^{368,369,370,371}

Rainfall changes (Figure 30.3) will affect island aquatic ecosystems. In Hawaiʻi, declines in dry-season streamflow will result in more intermittent streams¹³⁷ and loss of habitat connectivity and conservation value.³⁷² Decreased streamflow will also negatively impact stream organisms by reducing fitness and increasing disease and habitat for invasive fish and mosquitoes.^373,374,375

Across the region, climatic shifts are expected to impact native ecosystems via interactions with fire (e.g., Trauernicht 2019; Nugent et al. 2020^376,377). Wildland fires already burn a higher proportion of total land area in the Pacific Islands than in the continental US (Figure 30.13)^229,378 and are strongly linked to El Niño events.^49,103 While limited future climate projections indicate increasing fire probabilities,³⁷⁷ the future of fire in the region is highly sensitive to management and policy decisions, since ignitions are largely caused by humans (e.g., Dendy et al. 2022; Trauernicht et al. 2015^229,378). Education and outreach will continue to play a critical role in wildfire mitigation (e.g., HWMO 2021¹²⁵).

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Wildfires burn large percentages of land in Pacific Islands compared to the western US.

Figure 30.13. The annual percentage of total land area burned for seven Pacific Islands is equivalent to or greater than the percent area burned for western US states. Years examined are noted for each location. Figure credit: USDA Forest Service, USGS, NOAA NCEI, and CISESS NC.

Interactions between invasive species and climate change in isolated Pacific Islands are complex (KM 8.2),^{379,380,381,382,383} with climate change most often exacerbating invasion.^{384,385,386,387} Invasive species may aggravate local water stress, for instance, by using more water resources than native plants^{148,380,388,389} or by causing less rainfall to reach the forest floor, as in the case of strawberry guava invasion.^148,390 Similarly, fire-prone invasive vegetation is likely to further increase future climate-driven fire risk.³⁷⁷ With the steep increase in the number of naturalized species on Pacific Islands,³⁹¹ these climate and invasion interactions will become increasingly important for managers to address.³⁹² Critical region-wide investments are being made to prevent the introduction of potentially invasive species and diseases,³⁹³ given that climate change can alter pathways for species introductions.^394,395,396

Responding to Rising Threats

Regional efforts increasingly focus on restoration management that enhances climate resilience.^{397,398,399,400,401} Besides boosting adaptive capacity,⁴⁰² ecosystem restoration efforts may provide multiple benefits to islands, including hydrological (KM 8.3)^{140,148,161,401,403,404} and sociocultural benefits,^404,405 as well as carbon sequestration⁴⁰⁶ and sediment retention.⁴⁰⁷ Hawaiʻi and the USAPI have established both marine and terrestrial protected areas (Box 30.2),^{119,134,408,409} which elsewhere have successfully supported ecosystem resilience under climate change (e.g., Gaüzère et al. 2016; Lawler and Hepinstall-Cymerman 2010; Roberts et al 2017; Virkkala et al. 2014^{410,411,412,413}).

The urgency of conservation actions (Figure 30.14) is exemplified by the Hawaiian forest bird crisis. Forest bird populations are declining due to avian malaria spread driven by warming.^414,415 Managers are exploring options for safeguarding species near extinction,^{416,417,418,419} including habitat restoration, avian malaria vector control,⁴²⁰ and translocation.^{421,422,423,424}

In addressing these myriad challenges, conservation efforts increasingly involve broader partnerships with educators (e.g., Bolden et al. 2018¹²³) and Indigenous Knowledge holders, who play a vital role in conservation planning and implementation (KM 30.5; Ch. 16).^{405,425,426,427,428}

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Conservation efforts across the region help to restore ecosystem health and protect native species.

Figure 30.14. These images depict on-the-ground climate-related conservation actions across Pacific Island ecosystems: wildfire management in Hawaiʻi Volcanoes National Park (top left); planting native species in Palau to restore watershed health (bottom left); installing protective fencing around native habitat in Hawaiʻi (bottom center); conservation of native snails using captive populations to prevent extinction of vulnerable populations (top right); seabird translocations in the Northwestern Hawaiian Islands to safeguard against sea level rise (center right); and climate-resilient coral reef restoration experiments in Hawaiʻi (bottom right). Photo credits: (top left) D. Benitiez, NPS; (top right) © Chris A. Johns; (center right) © Lindsay Young, Pacific Rim Conservation; (bottom left) © Ann Singeo, Ebiil Society Inc.; (bottom center) NPS; (bottom right) Hawaiʻi Department of Land and Natural Resources.

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Reciprocal Relationships Between People and Place

Communities throughout Hawaiʻi and the USAPI demonstrate Indigenous cultural and community resilience grounded in Traditional Knowledge as they continue to adapt to global changes, just as their ancestors have for millennia (KM 18.3; Figure 16.3).⁸⁷ These adaptations and the collective resilience of Indigenous communities are strengthened and sustained through reciprocal exchanges between the peoples and the lands, territories, waters, and resources to which they are genealogically connected (Figure 30.15). Resilient communities are vital to the overall health and well-being of island peoples. To effectively advance the science of sustainability and manage resources amidst the changing climate, spiritual rituals and engagements are central to biocultural well-being—the collective well-being of landscapes, seascapes, and Indigenous communities (Box 30.6).⁴²⁹ Through these rituals and engagements, island communities individually and collectively are able to connect to the place and all of its life-forms, cultivating reciprocal relations that enhance future resource abundance based on responsibility rather than ownership.⁴³⁰

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The resilience of Pacific Island communities is strengthened by their connection to place and all of its life-forms.

Figure 30.15. Limu refers to ocean plants, including seaweed. The governor of Hawaiʻi designated 2022 as the Year of the Limu as a part of a statewide community effort to raise awareness about the importance of limu to Hawaiʻi’s cultural identity and the health of the nearshore marine environment. The KUA Limu Hui (a seaweed practitioners group) shares traditional knowledge and practices related to limu gathering, use, and restoration. Limu kala (Sargassum echinocarpum; left) is incorporated into various food dishes, is used as bait for reef fish, and is an important component in Hawaiian forgiveness ceremonies. Limu such as palahalaha (Ulva fasciata; right) also play a critical role in intertidal ecosystems as they provide food and shelter for invertebrates and herbivores. Photo credits: © Haunani Kane.

Cultural and Historical Sites

Archaeological, cultural, and historical sites are representations of the living culture and ancestral knowledge of Indigenous and island peoples, and they serve as potential resources and models as communities seek to remediate increasing climate risks and impacts (Figure 30.16).^{87,118,119,434} Indigenous communities are identifying and protecting cultural and historical sites, assessing climate impacts on natural resources, and creating restoration plans (KM 16.3).^435,436

Archaeological sites and oral history document the culturally grounded and traditional resilience of island peoples to historical coastal change that resulted from extreme events and higher sea levels. Approximately 2,000–4,000 years ago across the equatorial Pacific, sea level was at least 3.3–6.6 feet higher than present, which directly influenced the timing of atoll formation and the initial migrations and settlement of island people.⁴³⁷ Initial settlers of Majuro atoll, RMI, arrived within 100 years of island formation, when sea level was 3.3 feet higher than present, and they cultivated trees and shrubs into crop systems rather than waiting for natural vegetation succession.⁴³⁸ On Yap, FSM, coastal stone-built structures are expressions of innovation, cultural identity, and pride that allowed islanders to occupy coastal areas under elevated sea level, and modern structures such as the coastal men’s houses (faluw) and taro gardens document cultural resistance to rising waters.⁸⁷ On Guam, traditional CHamoru houses were elevated on limestone pillars (latte) along the coast, protecting them from coastal inundation.⁴³⁹ Across higher islands like Sāmoa, settlement along narrow coastal plains occurred after nearly 1,000 years of sea level fall and subsequent natural development of habitable coastal environments.⁴³⁷ The oral histories, stories, myths, storyboards (Palau), and songs/chants of Indigenous Peoples record their observations of the changing environments and lifestyles. The proverb He pūkoʻa kani ʻāina describes the natural evolution of a coral reef into an island and is also interpreted by Native Hawaiians to describe the resilience of a person who begins in a small way and gains steadily until she becomes firmly established.⁴⁴⁰

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Cultural sites, representing the living culture and ancestral knowledge of Indigenous Peoples, are at increasing risk.

Figure 30.16. Sea level rise (SLR), strong winds, and large storm waves impact a fishpond in Kaloko-Honokōhau, Hawaiʻi (left). Kukau El Bad, a cultural site in Ngarchelong State, Palau, is inundated by salt water and continues to be threatened by SLR, storm surge, and erosion (right). Photo credits: (left) © Kimberly Crawford; (right) © Ann Singeo, Ebiil Society Inc.

Across the region, one approach to mediating climate impacts is to reinvigorate and restore food production across landscapes (KMs 11.1, 30.1; Box 30.4).⁴⁴¹ This is being accomplished through several pathways. At a policy level, work is being done to amend law in Hawaiʻi to add a “Traditional Lands” zone under the state’s Land Use Commission that would streamline permit and building requirements¹⁹⁴ for eco-village-type living with mixed-use housing and other sustainable infrastructure such as commercial kitchen and food-processing facilities, as well as the use of traditional agriculture lands such as loʻi kalo (irrigated taro, agriculture), loko iʻa (fishponds), and large expanses used to traditionally farm staple crops such as ‘uala (sweet potato).⁴⁴² Communities and cultural practitioners are working with scientists to identify areas where food production could be expanded under future climate scenarios (KM 12.4). For example, taro cultivation was modeled under future SLR scenarios⁴³⁴ and sweet potato⁴⁴² and breadfruit under increasing temperature and rainfall scenarios,¹¹⁸ showing the potential resilience of these traditional agricultural practices.

Indigenous Knowledge Systems and Values of Ecosystem Services

Indigenous island communities are also working to ensure that Traditional Knowledge is central to resilience strategies (KM 16.3). A growing body of Indigenous-led research describes how biocultural methods can successfully be incorporated into efforts focused on community-based subsistence,^431,432 relationships to place,⁴³³ cultural–ecosystem service assessments,⁴⁴³ and the protection of historical and cultural resources.⁴⁴⁴ Biocultural approaches start with and build upon local cultural perspectives by encompassing values, knowledge, and needs and by recognizing reciprocal restoration between ecosystems and human well-being (KM 20.3).^195,443 The act of restoring ecosystem services contributes to cultural revitalization⁴³³ by reaffirming connection to place, enhancing community relationships and social networks and the physical and mental well-being of Indigenous Peoples,⁴⁰⁵ increasing local food production,²⁰² and diversifying the local economy⁴²⁷—all while distributing the abundance through reciprocal exchange.⁴³¹ In return, the renewal of culture promotes the restoration of ecological integrity through the creation and expansion of habitat for native species⁴³⁴ and further supports recovery and resilience of ecosystems following future environmental disturbances (KM 8.3).⁴⁴⁵ Equitable outcomes from climate research and planning are predicated on properly citing Indigenous elders and knowledge keepers,⁴⁴⁶ enhancing Indigenous control of Indigenous data via data sovereignty, protecting intellectual property rights, and establishing free, prior, and informed consent (KMs 16.2, 20.2, 31.2).^447,448

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