While the lands, waters, and other natural resources of Indigenous peoples hold sacred cultural significance, they also play a principal role in ensuring the viability of these communities’ economies and livelihoods.^5,8 Tribal trust lands provide habitat for more than 525 species listed under the Endangered Species Act, and more than 13,000 miles of rivers and 997,000 lakes are located on federally recognized tribal lands.⁹ For many tribes, despite this endowment of natural resources, median household income is only 69% of the national average median income.¹⁰ Challenges to economic development for federally recognized tribes are in part related to institutional barriers to tribal self-determination stemming from federal trust authority over tribal trust lands.^8,11 Due to past federal polices, including the Dawes Act (1887) and Indian Reorganization Act (1934), most reservation lands today constitute a checkerboard pattern of trust and fee-simple (private) land ownership, highly fractionated government trust lands with many owners, and trust lands subject to ongoing federal oversight in resource management decisions.^12,13,14,15 These issues are complicated further when multiple or overlapping federal, state, or local government jurisdictions are involved.¹⁶

Historical and ongoing federal oversight of natural resource management on tribal lands can, in some cases, hinder growth in tribal and individual natural resource-based business enterprises, because tribes lack the autonomy to determine their own property rights and related institutions.^17,18 Similar critiques of historic and contemporary U.S. policy have been identified in studies of Indigenous climate change adaptation.^19,20 Non-federally recognized tribes lack legal status to qualify for federal funding and economic development support, though some are eligible for state support.²¹ Funding limitations are often identified as a barrier to the planning or implementation of climate adaptation or mitigation actions,²² which suggests that increased economic revenues could create opportunities for tribes to choose to pursue climate actions.

Many Indigenous peoples continue to express their cultural relationships with ancestral lands through traditional subsistence economies. Such economies rely on local natural resources for personal use (such as food, shelter, fuel, clothing, tools, transportation, and arts and crafts) and for trade, barter, or sharing. Climate change threatens these delicately balanced subsistence networks by, for example, changing the patterns of seasonal timing and availability of culturally important species in traditional hunting, gathering, and fishing areas.^{4,5,7,22,23,24,25,26,27,28,29,30,31,32} Each of the Fourth National Climate Assessment’s regional chapters includes at least one example of climate impacts or adaptation related to Indigenous subsistence species or practices.

Most Indigenous peoples across all regions of the United States pursue a mix of traditional subsistence and commercial sector activities that include agriculture, hunting and gathering, fisheries, forestry, energy, recreation, and tourism enterprises.^{5,22,33,34,35} Observed and projected changes of increased wildfire, diminished snowpack, pervasive drought, flooding, ocean acidification, and sea level rise (Ch. 2: Climate) threaten the viability of each of these enterprises.^{22,29,33,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52} Tribal casino properties, for example, often include water-dependent recreational amenities that, due to pervasive drought, are impacted by changes to local water regimes,⁵³ and some tribes account for this in their adaptation plans, such as the Confederated Salish and Kootenai Tribes⁵⁴ and the Lummi Nation.⁵⁵ In addition, Indigenous agriculture is already being adversely affected by changing patterns of flooding, drought, dust storms, and rising temperatures, with future projections varying by region but indicating increased soil erosion and irrigation water demand and decreased crop quality and animal herd sizes (Ch. 25: Southwest, KM 4 and 6).^{22,41,52,56,57,58} Some tribes include consideration of subsistence and commercial economic resources in their adaptation plans. For example, the 1854 Treaty Authority Adaptation Plan,⁵⁹ which includes the Bois Forte, Fond du Lac, and Grand Portage Tribes, provides detailed adaptation strategies customized to protect and sustain walleye, sturgeon, moose, and wild rice, among others (Ch. 21: Midwest). Similarly, the Confederated Tribes of the Umatilla Indian Reservation⁶⁰ have identified climate risks to salmon, elk, deer, roots, and huckleberry habitat (Ch. 24: Northwest, KM 2).

Federal and state legal frameworks and regulatory actions can compound physical climate change stressors on Indigenous peoples’ subsistence economies and act as a barrier to climate change adaptation. For example, federal and state fish and wildlife regulations, such as endangered species listings, are meant to respond to species population declines that can be exacerbated by climate change (Ch. 7: Ecosystems), but they can further stress Indigenous subsistence economies that have traditionally relied on those species.^61,62,63 Such regulatory actions taken without the input of Indigenous peoples can limit traditional sources of income, such as arts and crafts that are part of Indigenous economies. For example, some Alaska Natives utilize skins, furs, and walrus tusks to support local subsistence economies and to produce clothing and crafts that support local tourism.^64,65

Another recognized barrier to economic self-determination and climate adaptation for federally recognized tribes with resource constraints is the costly and lengthy process to quantify, secure, and use appropriated water rights.^{7,41,53,66,67,68} This is particularly the case in the arid western United States, where the majority of reservation land acreage is located and where prior appropriation doctrine is the primary mechanism for allocating scarce water resources.⁶⁶ As water becomes more scarce and regional demands increase, the quantification of water rights is viewed by many as necessary to design and plan adaptation strategies that secure water for various uses: cultural, municipal, recreational, agricultural, fisheries, and aquatic resources, among others.^{4,19,58,66,67,69,70,71} To date, approximately 30 reservations have engaged in water rights settlements,⁷² and while research shows that water rights quantification can positively affect tribal economies, additional analysis is necessary to better understand these effects.⁶⁶

Infrastructure and linked systems that support Indigenous economies and livelihoods are at risk from more frequent or intense heavy downpours, floods, heat waves, wildfires, and droughts, as well as higher sea levels and storm surges.^19,49,73 As shown in Figure 15.2, Indigenous peoples are vulnerable to infrastructure disruptions that can occur at the level of an individual household (for example, housing and sanitary water supply); within larger regional, integrated systems (such as for power, transportation, and telecommunication) (Ch. 17: Complex Systems); or within human systems that rely on such infrastructure to provide other essential services (such as emergency medical response). This vulnerability is partly due to long-standing, unmet infrastructure needs and deferred maintenance challenges.⁷⁴ For example, many Indigenous communities lack sufficient water delivery and treatment facilities and the operating capital needed to maintain and/or improve those facilities.^41,75,76

Indigenous peoples also have unmet needs and challenges in the energy sector. The evolution of the federal trust doctrine, and its associated timely and costly regulatory oversight of resource use on tribal trust lands, challenges federally recognized tribes’ ability to secure outside investments in energy and related infrastructure development (Ch. 4: Energy, KM 3; Ch. 29: Mitigation).^77,78 In addition, non-tribal entities operate the majority of energy development on tribal land, reducing opportunities for tribal workforce development and capacity building for self-directing future energy projects.⁷⁹ Still, energy development, particularly renewable energy, that is implemented in accordance with Indigenous values holds promise as a source of revenue, employment, and economic self-determination.^22,80 While not all Indigenous communities support energy development due to concerns about cultural and environmental impacts, there are a number of examples of growing interest in renewable energy.⁷⁹ The Pueblo of Jemez, for example, has developed the Nation’s first utility-scale solar project on tribal lands, and other tribes view renewable energy as a key strategy for climate mitigation.²² Tribes have also identified small-scale distributed electricity generation systems and energy efficiency as supporting their climate adaptation goals through increased energy independence.^22,79

Physical health risks and impacts to Indigenous peoples are the same as those faced by the general U.S. population (Ch. 14: Human Health); however, certain factors, known as the social determinants of health, are unique and contribute to the increased vulnerability of Indigenous peoples to adverse and potentially severe or fatal health outcomes (Box 15.1). Conventional Western science approaches to measuring and analyzing Indigenous health, adaptive capacity, health disparities, and environmental justice issues typically do not capture many of the key elements of health and resilience that are important to Indigenous populations.^{81,82,83,84,85,86} These elements emphasize non-physiological aspects of health, which include concepts related to community connection, natural resources security, cultural use, education and knowledge, self-determination and autonomy, and resilience.^83,84 For example, the Swinomish Indian Tribal Community has used shellfish beds and shoreline armoring as indicators to evaluate health in the context of a changing climate.⁸¹

Indigenous peoples have a unique and interconnected relationship with the natural environment that is integral to their place-based social, cultural, and spiritual identity; intangible cultural heritage (traditions or living expressions transmitted and inherited through generations); and subsistence practices and livelihoods.^{61,82,87,99,100} Climate change impacts to ecosystems (Ch. 7: Ecosystems) alter the relationships between humans and animals, between individuals, and within and between communities; these relationships are central to Indigenous physical, mental, and spiritual health.^{82,86,101,102} This alteration in relationships occurs when individuals, families, and communities (within and between generations) are less able or not able to share traditional knowledges about the natural environment (such as where and when to harvest or hunt), food, and ceremonial or cultural objects, among other things, because the knowledge is no longer accurate or traditional foodstuffs and species are less available due to climate change. For many Indigenous peoples, the act of sharing is fundamental to these intra- and intergenerational relationships, sustains cultural practices and shared identity, and underpins subsistence practices.^44,103 A projected health-related consequence of reduced or lost access to the knowledge, experiences, and relationships built on sharing is increased food insecurity for households reliant on subsistence practices.⁶¹ For example, in Alaska, changes in sea ice coverage and thickness and the timing of ice formation (Ch. 9: Oceans; Ch. 26: Alaska) can lead to decreased access to hunting and fishing areas, which can mean people are unable to access food sources (that is, loss of cultural use.⁸¹ This can then result in lost opportunity for the social components of these activities, including reduced community connection (e.g., Donatuto et al. 2014⁸¹), less food and knowledge sharing, and diminished relationship building.^44,61

Communities that rely on the natural environment for sustenance and livelihoods are at increased risk for adverse mental health outcomes related to climate change.¹⁰⁴ Many Indigenous communities share a focus on relationships between people and wildlife and on a respect for natural resources.^29,81,105 Climate impacts to lands, waters, foods, and other plant and animal species undermine these relationships, affect place-based cultural heritages and identities, and may worsen the historical trauma still experienced by many Indigenous peoples.^86,101,102 For example, in Arctic Indigenous communities, changing wildlife and vegetation patterns are disrupting traditional and subsistence practices and have been associated with increased rates of mood and anxiety disorders; strong emotional responses; and loss of connections to homeland, social networks, and self-worth.^82,101 Additionally, climate impacts that degrade water quality can adversely affect sacred water sources and aquatic species on which subsistence livelihoods and associated relationships are based, increasing the risk of mental health impacts in addition to the well-studied physical health concerns.^53,71 Damage to cultural heritage sites from climate change can affect mental health through impacts to cultural, economic, and social relationships.¹⁰⁶ Media imagery and reports or stories of climate risks and vulnerability also lead to psychological trauma or increased anger, anxiety, depression, fear, and stress.¹⁰⁷ These impacts can intensify existing social stressors, such as loss of jobs and social connections, loss of social support, and family distress.^101,104

Climate change adaptation measures can reduce physiological vulnerability to health risks; to date, most observational evidence comes from behavioral and public health responses to extreme heat.^{108,109,110,111} Organizations including the National Indian Health Board and the Alaska Native Tribal Health Consortium have ongoing efforts to increase Indigenous adaptive capacity specifically for health. Some tribes have climate vulnerability assessments that acknowledge the role of traditional subsistence species, or First Foods, as an essential aspect of health and tribal resilience; for example, the Yurok Tribe assesses the role of salmon in community health,¹¹² and the Confederated Tribes of the Umatilla Indian Reservation⁶⁰ discuss climate risks to salmon, elk, deer, roots, and huckleberry habitat (Ch. 24: Northwest, KM 2). In the Republic of the Marshall Islands, a community-led planning process known as Reimaanlok incorporates traditional knowledge and facilitates local self-determination to support shared goals of climate adaptation, natural resource management, and community health.⁸⁵

Indigenous peoples have a long and rich history of adaptation to climate variability^1,71,113,114 that is rooted in their dynamic relationships to the natural environment.¹¹⁵ However, the ability of Indigenous peoples to anticipate and respond to climate change is affected by economic, social, political, and legal considerations that severely constrain their abilities to consider and respond to rapid ecological shifts. Despite the many examples of Indigenous peoples undertaking climate vulnerability assessments and adaptation planning (see Figure 15.1 for links to information on current adaptation efforts), as the pace of ecological changes increases with climate change, and sociopolitical obstacles to implementing responses continue to exist, there are challenges and barriers to adaptation.^116,117

Incorporating Indigenous Knowledges in Adaptation

Indigenous knowledge systems can play a role in advancing understanding of climate change and in developing more comprehensive climate adaptation strategies,^6,7,118 in part because they focus on understanding relationships of interdependency and involve multigenerational knowledge of ecosystem phenology (the study of cyclic and seasonal natural phenomena)^6,119,120 and ecological shifts.^25,121 For example, Inupiat residents in Alaska have identified cyclical patterns of coastal erosion, and their understanding of how quickly and in which direction wind and wave energy reaches the coast can help communities prone to flooding.¹²² Indigenous adaptation planning, including considerations of issues such as flooding and water rights, benefits from a greater focus on participatory planning in natural resource management.^{19,22,123,124,125,126} This planning incorporates local knowledge and values from conception through implementation^127,128,129 in ways that ensure the protection of Indigenous knowledges and Indigenous peoples’ rights not to share sensitive information.²² In this way, traditional ways of knowing are contributing to sustainable land management practices under changing environmental conditions.^{130,131,132,133} For example, the Wabanaki Nations of Maine work closely with local researchers, foresters, and landowners as part of the Cooperative Emerald Ash Borer Project to precisely catalogue and map the decline of the native black ash deciduous trees on which these communities rely for economic, cultural, and spiritual practices. The cooperative leverages Indigenous knowledge of environmental history as it relates to the invasive emerald ash borer beetle.¹³¹ Additionally, the Nez Perce Tribe employs Indigenous knowledges as part of an initiative to enhance local salmon populations that have been in decline (Ch. 24: Northwest, KM 2). For more on Indigenous knowledges, see the regional chapters in this assessment.

Limited Access to Traditional Territory and Decision-Making

Historically in North America, Indigenous peoples occupied vast amounts of land and had access to a wide range of natural resources. Under these conditions, high mobility provided a robust response to changing environmental conditions,¹²² but such options today are limited or nonexistent. Multiple considerations, such as whether tribes have corporate status, federal recognition, reservation lands, off-reservation resource rights, specified water rights, access to Ceded Territories and traditional resources, among many others, affect how Indigenous communities develop and implement climate adaptation efforts.²² Specifically, limitations on the abilities of tribal individuals, communities, businesses, and governing bodies to manage land, participate in policymaking, and access various resources can act as barriers to climate adaptation efforts. Federally recognized tribes have access to a distinct array of resources, programs, and legal authorities, yet they still face numerous limitations in their abilities to implement adaptive strategies. For example, when ecosystems or species’ habitats or migration routes shift due to changes in climate, tribes’ rights to gather, hunt, trap, and fish within recognized areas are constrained by reservation or other legally defined borders, making adaptation more challenging.^22,40,48,134 This is also the case when federal or state regulations fail to prioritize Indigenous peoples’ access to traditional resources. Tribes with noncontiguous reservation lands can be negatively impacted by non-tribal landowners who do not support climate adaptation efforts, and many Indigenous peoples lacking federal recognition often lack the autonomy, funding, and governmental support to address climate change.^{31,48,135,136} Because of these and other considerations, decisions regarding natural resource use are often made without appropriate consultation and collaboration with Indigenous peoples,¹⁹ a process that further inhibits local adaptive capacity.

Disaster Management

As in many communities, Indigenous peoples are experiencing climate change impacts from more frequent and severe weather events, including drought, heat waves, hurricanes, torrential downpours, and flooding (Ch. 2: Climate).¹³⁷ In recent years, the Federal Government has made amendments to disaster recovery laws that provide more autonomy to tribes in managing disaster recovery, including the Sandy Recovery Improvement Act of 2013, which grants tribes the authority to request a disaster declaration and assistance from the President, instead of relying on state authorities.¹³⁸ However, many tribes continue to face hurdles to disaster management and disaster risk reduction planning. A study of tribes’ participation in the federally run and subsidized National Flood Insurance Program finds that, as of 2012, only 7% of tribal communities were participating in the program due to lack of information, limited local government capacity, and limited land jurisdiction.¹³⁹

Risk management and feasible adaptation options are also limited by fundamental issues with federal disaster funding that can be especially prohibitive for tribes. Federal programs are designed to offer extensive emergency relief after disasters have occurred, but they have only limited funding for hazard mitigation or preparation for long-term environmental change.¹⁴⁰ Most slow-onset disasters, such as erosion, are absent from the Federal Government’s primary disaster recovery legislation, the Stafford Act, making it particularly challenging to prepare for changing coastlines.^141,142 Additionally, the low population and rural contexts of many Indigenous communities limit the score they can receive in state and federal cost–benefit analyses, which also severely limits funding for disaster risk reduction.^140,143,144

Displacement and Relocation

Many Indigenous peoples are now facing relocation due to climate-related disasters, more frequent coastal and riverine flooding, loss of land due to erosion, permafrost thawing, or compromised livelihoods caused by ecological shifts linked to climate change.^{7,122,145,146,147} Throughout the 18th, 19th, and 20th centuries, Indigenous peoples were removed in large numbers from their homelands by settler colonial governments, leading, in many cases, to death, diaspora, and socioeconomic struggles. The historical context of forced relocations of Indigenous peoples emphasizes the need for relocation frameworks that protect self-determination.^{120,144,146,148}

In various regions of the United States, communities of Indigenous peoples are considering relocation or actively pursuing relocation as an adaptation strategy, including communities in Alaska, the Southeast, the Pacific Islands, and the Pacific Northwest (Figure 15.3) (Ch. 19: Southeast; Ch. 24: Northwest; Ch. 26: Alaska; Ch. 27: Hawai‘i & Pacific Islands). The complex barriers to adapting to these extreme circumstances continue to be the lack of statutes and regulations, legal authority, and governance structures that enable federal, state, and local actors to coordinate funding priorities and regulations.⁷ For example, many tribal communities facing slow-onset disasters, as described above, fail to qualify for relocation funds because they have not been declared federal disaster areas. Also, because there is no single, comprehensive federal program to assist tribes with relocation efforts, tribes must rely on project-specific funding streams that are not designed for relocation initiatives and that often have conflicting requirements and priorities.¹⁴⁷ These barriers are even more challenging when tribes lack federal recognition.^146,149 Additionally, there is no clear platform through which communities can connect non-Indigenous scientific information with their own knowledge systems to inform local decision-making processes as to whether adaptation is best achieved through relocation or by protecting in place through capital investments such as flood management infrastructure.^150,151 Finally, even if relocation is agreed on and logistically feasible, the challenges associated with maintaining community and cultural continuity often undermine the objective of the adaptation strategy, and models for mitigating the impacts of relocation on cultural institutions are rare and difficult to replicate.¹⁵²

In the past few years, solutions have emerged to better address the need for community-driven relocations, but even these have proven more complex for tribal communities than originally expected. The state-recognized Isle de Jean Charles Band of Biloxi-Chitimacha-Choctaw of Louisiana, in partnership with the Lowlander Center (Figure 15.4), developed a community resettlement plan that was selected in 2016, in conjunction with the State of Louisiana’s application to the National Disaster Resilience Competition, to receive funding from the U.S. Department of Housing and Urban Development. Due to restrictions on the funding included within the legislation and the tribe’s lack of federal recognition, the state is managing the resettlement of the entire island community, which limits tribal authority over relocation plans. This arrangement exemplifies one way in which tribes are limited in deploying adaptation strategies when using funds that are not specifically designed to meet the unique needs of tribal communities (Ch. 19: Southeast). Though promising, this solution, to date, is a pilot program through a one-time competitive funding opportunity, and there is no planned ongoing support for other community-led resettlements. Outside of this pilot program, the most promising funding options for facilitating relocations away from changing coastlines are voluntary buyout programs offered by some local, state, and federal entities, but new research suggests that these are particularly ill-suited to tribes because of their focus on individual households, instead of community-wide relocations.¹⁵³ Central organizing institutions, such as the Denali Commission that is assessing relocation challenges for communities in rural Alaska, may help provide structure for joint state, federal, and tribal partnerships for pursuing safe, timely, and culturally appropriate relocation. More research would be required to properly assess whether these and other solutions would facilitate action toward safe and self-determined futures for these communities.