Fifth National Climate Assessment
8. Ecosystems, Ecosystem Services, and Biodiversity

Ecosystem changes can be driven by physical factors (e.g., thermal stress), biological responses (e.g., changing ranges), or both, often interacting with stressors from human activities. Multiple stressors, both gradual and episodic, can have complex interactive or amplifying effects on ecosystems (Figure 8.4);^17,18 for example, severe hurricanes can heighten forest vulnerability to drought and/or fire.^19,20

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Climate effects on watersheds exemplify the amplifying impacts of gradual and episodic stressors.

Figure 8.4. Both gradual and episodic (short-lived) climatic drivers alter the transport of water, nutrients, and sediments from terrestrial watersheds to downstream water bodies. These drivers affect aquatic ecology and ecosystem services throughout the hydrological system, even in areas distant from drivers of change (e.g., more intense rainfall leading to leaching of fertilizers that stimulate harmful algal blooms downstream).²¹ The frequency and intensity of episodic extreme events is projected to increase (KM 2.2), raising risks for many species (Figure 8.10). Figure credit: Cary Institute of Ecosystem Studies.

Many ecosystems are at increased risk of ecosystem tipping points (where rapid and unpredictable conversions to new states occur),²² although it is difficult to predict how, where, and when these changes will occur.^23,24 Transformative changes in the composition, structure, function, and other properties of ecosystems result in a new stable state, or regime, with a different combination of species and communities, often resulting in reduced biodiversity and ecosystem services.^25,26 Restoring an ecosystem may be difficult or even impossible if a critical threshold or tipping point is crossed and a different system emerges, because changing or restoring the drivers that led to the altered state may not result in a return to the original state (Figure 8.5).²⁷

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The Arctic faces substantial impacts from thawing permafrost that cannot be reversed.

Figure 8.5. Thawing of permafrost can cause irreversible tipping points in Arctic landscapes, transforming intact ecosystems (left) to severely altered ones (right), with impacts on people. A warming climate and fires lead to melting ground ice. Arctic and boreal forests contain permafrost soils with excess ice (more than is contained in soil pores), which form 3D networks in the ground. With warming, this ground ice can melt and the ground surface collapses (A). Fires, a natural part of the boreal disturbance cycle, are increasing in extent, frequency, and severity. Melting ice can lead to accumulation of water in ponds, lakes, and wetlands, but continued thawing can cause lakes to drain. Permafrost can also thaw abruptly, causing thaw slumps and bank failures (B). These geomorphological changes impact human infrastructure (C) and access to the land (D). Other risks (not pictured) include chemical and potentially disease mobilization that can threaten human health and ecosystems.^28,29 Human adaptation strategies to permafrost thaw include installing firebreaks around infrastructure (E). Adapted from Schuur et al. 2022³⁰ [CC BY 4.0].

Ecosystem changes can be gradual or relatively abrupt³¹ and depend in part on ecosystem characteristics and key species.³² Ecosystems with immobile or long-lived species such as corals or trees can often exhibit abrupt responses because they have limited capacity to keep pace.^33,34,35 Ecosystems with higher biodiversity have more species interactions and often exhibit slow changes at first followed by abrupt shifts.¹⁵ Multiple stressors can lead to synergistic effects and trigger abrupt changes.³⁶ Examples include the co-occurrence of extreme heat, drought, and invasive grasses (Figure 8.6)²² or wildfires followed by insect infestations (or vice versa; Focus on Western Wildfires).

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Climate change interacts with other stressors to cause synergistic effects, and resulting ecosystem changes can be abrupt and difficult to reverse.

Figure 8.6. In the western US, drought and longer, hotter growing seasons combined with invasive grasses and overgrazing have transformed sagebrush shrublands past a tipping point into annual grasslands that experience more frequent wildfires and no longer support native biodiversity and livestock grazing. Removing invasive grasses and seeding with native plants often does not restore the original shrubland ecosystem.³⁷ Adapted from Foley et al. 2015³⁸ [CC BY 4.0].

Vulnerability of ecosystems to climate change depends on exposure to the physical drivers of change and characteristics that affect species’ sensitivity and capacity to adapt.³⁹ Examples of vulnerable ecosystems experiencing transformation are increasingly common (Figure 8.7). There is evidence that ecosystems with higher biodiversity are more resilient in the face of climate change,^40,41 indicating that better protection and reduced fragmentation and degradation of ecosystems are potential climate-adaptation strategies.⁴²

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Transformations to ecosystems are already noticeable and widespread.

Figure 8.7. There are numerous and widespread examples of ecosystems transforming to altered states, with complex drivers and outcomes.^{22,43,44,45,46} Climate-driven ecological transformations are occurring in all regions of the US and often negatively impact the services these ecosystems provide, including regulation of carbon and water cycles, wildlife habitat, and recreation. Figure credit: USDA Forest Service, USGS, and NOAA Fisheries. Photo credits (clockwise from top right): John Bradford, USGS; Steve Lonhart/NOAA; ©Elizabeth-Ann Jamison; Ilsa B. Kuffner, USGS; Sarah K. Schoen, USGS; ©Nicholas Smith; John Bradford, USGS; ©Anna Armitage.

Monitoring Transformations

Identifying and monitoring species or ecosystem traits that provide early warnings of vulnerability, system-wide decline, or tipping points can assist in reducing risks.^26,47,48,49 Numerous long-term monitoring networks (Figure 8.8) have been established in recent decades in direct response to climate and other changes.^27,50 Community-led (“citizen”) science efforts such as iNaturalist⁵¹ and the USA National Phenology Network,⁵² alongside community-based monitoring networks⁵³ and Indigenous Knowledge holders (KM 16.3)⁵⁴ also collect observations across large areas⁵⁵ and have helped detect altered species distributions, abundances, and phenologies.^56,57,58

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Monitoring programs are critically important for observing and projecting trends in resilience, species invasions, range shifts, declines, and extinctions.

Figure 8.8. Federally operated networks (NPS I&M, NERR) and other long-term networks (LTER, LTAR, NEON, MBON, AmeriFlux) provide consistent and permanent observations at limited sites, whereas volunteer networks (USA-NPN, Indigenous Sentinels) offer more opportunistic observations across a wider landscape. Together, these networks provide critical data for understanding species and ecosystem changes, although gaps in coverage remain. Figure credit: Lynker and USGS.

Addressing Risks and Managing for Change

Climate change and other disturbances that transform ecosystems create growing management challenges.^14,59 Building, preserving, or restoring ecosystems is often the most practical and effective resilience strategy;^60,61 however, ecosystem transformation may still be inevitable.⁶² Conventional resource management approaches are often ill-suited for managing uncertainties and related trade-offs.^63,64 In contrast, adaptive management iteratively plans, implements, and modifies strategies for managing resources under uncertainty. Successful adaptive management requires an overarching adaptive governance approach that provides institutional structures and decision-making processes for coordinating efforts across scales,⁶⁵ managing uncertainties and conflicts,^66,67 mobilizing diverse knowledges, and addressing stakeholder interests.^68,69,70

Decision frameworks designed to anticipate ecosystem transformation can advance adaptative management processes (Figure 8.9).⁷¹ As one example, the Resist–Accept–Direct (RAD) framework helps identify conditions where ecosystem management can resist a trajectory of change, accept change, or direct change toward desired future conditions (Figure 8.9).^62,72 To engage the “direct” in their RAD planning, Tetlin National Wildlife Refuge in Alaska is combining scenarios, adaptive management, and adaptive pathway planning to engage managers and stakeholders to explore potential transformations, with one focus specifically on subsistence hunting.⁷³

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Decision frameworks can help plan for the potential transformation of ecosystems.

Figure 8.9. Two examples of adaptive decision frameworks are the Corals and Climate Adaptation Planning cycle (a) and the Resist–Accept–Direct (RAD) framework (b). In (a), users are guided through assessment and design considerations to adjust climate-smart management interventions. In (b), the current ecosystem (gray) is affected by either moderate or strong transformational forcing that drives decisions (black dots) to resist (red time periods), accept (yellow time periods), and direct (green time periods) the trajectory of change. (a) Adapted from West et al. 2017, 2018^74,75 [CC BY 4.0]; (b) adapted from Lynch et al. 2022.⁷²

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Climate-related stressors and other drivers of global change, such as land-use change, habitat destruction, and overexploitation, can create significant biodiversity changes and losses (Figure 8.1).^76,77 Even short-term extreme events such as heatwaves^78,79,80 can generate significant species impacts. For example, coral reefs are threatened by cumulative impacts of ocean warming and acidification, marine heatwaves resulting in bleaching and higher susceptibility to diseases, increasingly powerful tropical cyclones causing loss of structural complexity, hypoxia (low oxygen) events, overfishing, and pollution (Figure 8.10a, b; Box 10.1; KMs 9.2, 10.1).^{81,82,83,84,85,86} Similarly, wildfires (Focus on Western Wildfires)⁸⁷ can create risks for some species both directly (Figure 8.10c, d) and indirectly through longer-term habitat changes.⁸⁸

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Short-term extreme events can have severe impacts on threatened species.

Figure 8.10. Two examples of such impacts are as follows. (a) High water temperatures off Southeast Florida exceeded the maximum average monthly temperature (horizonal line in time series) in 2014–2015, resulting in severe bleaching of (b) pillar coral (Dendrogyra cylindrus) colonies and subsequent disease and death of all individuals. (c) Wildfires impacted more than 75% of breeding pairs (blue polygons) of (d) Mexican spotted owl (MSO; Strix occidentalis lucida) in Smokey Bear Ranger District, New Mexico, in 2012. Figure credits: (a) adapted from Jones et al. 2021⁸⁹ [CC BY 4.0]; (c) USDA Forest Service, NOAA Fisheries, and NOAA NCEI. Photo credits: (b) ©David Gilliam, Nova Southeastern University; (d) ©Serra J. Hoagland, USDA Forest Service.

Changes in Phenology

Compounding the responses of species to extreme events, the timing of seasonal events such as leaf-out, flowering, migration, spawning, phytoplankton blooms, and egg hatching is changing in response to rising winter and spring temperatures and to the altered timing and amount of snowmelt and rainfall (Figures 8.8, A4.13).^58,90,91,92 Changes include earlier flowering and maturity in agricultural crops that affect planting and harvest times,^{93,94,95,96,97} longer and more intense allergy seasons (KM 14.4),⁹⁸ and increased pest activity.^99,100 Changes are most pronounced at high latitudes and elevations and in urbanized areas.^101,102 Phenological mismatches emerge when the timing of activities in interacting species changes at different rates, such as food availability shifting to no longer match a dependent organism’s needs.^103,104 Phenological changes are also impacting seasonal carbon cycling¹⁰⁵ and increasing vulnerability to spring frost damage (App. 4).¹⁰⁶ There are significant economic and social impacts of these changes, including tourism impacts and loss of culturally important species.^107,108

Range Shifts

Elevational and latitudinal range shifts driven by climate change have already occurred for multiple species (Figure 8.11),^109,110,111 with range shifts of marine species more responsive and greater in magnitude than terrestrial ones (KM 10.1; Figure A4.12).¹¹² Mountaintop ranges are shrinking as species shift upslope, with high-elevation ones highly vulnerable.^113,114 Milder winters and warmer growing seasons are expected to expand ranges for some species.^115,116

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Climate change is leading to shifts in phenology and range for species across the United States.

Figure 8.11. Many plant and animal species are shifting to higher elevations, to more northern latitudes, or in multiple directions (here labeled “regional advancement”). The timing of seasonal activity is similarly shifting in response to warmer temperatures and changing precipitation regimes, in many cases occurring earlier in the year, although the direction and magnitude of changes are species-specific. Figure credit: University of Arizona and USFWS.

Art × Climate

Pamela DeChellis
Reflections in Pink
(2022, digital photography)

Artist’s statement: Early in the morning at Huntington Beach State Park in South Carolina, I found myself alone with this beautiful spoonbill, who was gently wading and preening in the morning light. Traditionally the spoonbill is most common in coastal Florida, Texas, and parts of Louisiana. Recently, we have seen spoonbills expand their range into South Carolina, in part because of climate change. As more northern areas get warmer they 'flock' to these areas. As the sea level rises, the more southern waters also get too deep for them to forage.

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Artworks and artists’ statements are not official Assessment products.

Conditions can change over very localized scales, creating complex “mosaic” patterns of environmental stressors.^{117,118,119,120} Climate refugia occur in locations where environmental conditions are changing more slowly than in surrounding areas¹²¹ or where local drivers override more regional-scale processes.¹²² These refugia are expected to support organisms that can repopulate other depleted areas through dispersal via currents or land corridors¹²³ and are therefore a priority for conservation (Figure 8.12).^124,125 Identification of the many existing refugia expected to disappear under climate change is crucial.^126,127

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Climate refugia are locations where environmental conditions are changing more slowly than in the surrounding region.

Figure 8.12. Refugia help populations survive extreme events, and when connected via dispersal currents and corridors can serve as rescue sites.¹²² Understanding variations in environmental exposures and organism sensitivities to extreme conditions helps forecast climate impacts^122,127 and inform management strategies.^128,129 Adapted from Morelli et al. 2016¹³⁰ [CC0 1.0].

Species Sensitivities and Extinction Risks

Understanding species sensitivities to climate impacts and adaptive capacity can help detect ecological tipping points (KM 8.1).^131,132 Large-bodied animals (Box 8.1)¹³³ and species occupying polar habitats are particularly at risk of local extinction due to physiological vulnerabilities.¹³⁴ In contrast, smaller-bodied species often have more widely variable responses to changing conditions (Figure 8.13).

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Insect pollinator responses to environmental stressors, even within the same taxonomic grouping, can vary widely.

Figure 8.13. Pollinator responses to changing climate conditions within a short time frame (the past 10–30 years) are leading to complex patterns of species movements across the landscape. Several species of bumble bees (panel 1) have had different responses over the past 10 years, from shifting in habitat within their ranges to range contractions and extinction risks. In panel 2, butterfly species are responding with declines and shifts within existing ranges or with range expansions nationwide. Figure credit: Colorado State University.

Art × Climate

Ananya A.
Youth Entry, Grade 9

A Desperate Ocean
(2023, acrylic)

Artist’s statement: The North Atlantic right whale is a critically endangered whale that inhabits the east coast waters of the United States. Human activities and climate change have driven down their numbers. I hope this piece will be a cry for help, something that will leave people with a sense of urgency. I also wanted to bring hope; the whale is escaping the entanglements. The sorrowful situation of the North Atlantic right whales can only be solved by us, humans, and if we all commit to it, I believe we can do it.

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Artworks and artists’ statements are not official Assessment products.

Disease Risks

Disease threats to wildlife, plants, and humans have emerged as a significant climate change risk.^{142,143,144,145,146,147} Climate change promotes range expansions and population growth of disease-spreading (vector) species, increased host susceptibility via stress, and enhanced pathogen transmission (Table 8.1; KM 15.1),¹⁴⁸ with major economic consequences.^149,150 Diseases often thrive where other stressors are present; prevalence is projected to further increase as populations and ecosystems become stressed from temperature variation and extreme events, changes in habitats, altered migration patterns and ranges, biodiversity loss, and increases in invasive species (KMs 15.1, 30.4; Figure A4.16).^{151,152,153,154}

Invasive Species Risks

Climate change has created uncertainty about where and how fast invasive species will spread, but there are both observed cases¹⁶⁴ and projections showing expected increases.¹⁶⁵ For example, cold-sensitive invasive species such as the kudzu vine (Pueraria montana var. lobata) can spread northward with warming.¹⁶⁶ Some invasive species are more successful than natives—particularly certain terrestrial plants¹⁶⁷ and aquatic species¹⁶⁸—because they better tolerate or more rapidly adapt to changing conditions (Figure 8.15). Yet not all invasive species are favored by climate change; many invasive plants and vertebrates may experience decreased ranges while the ranges of many invasive invertebrates and pathogens are expected to increase.¹⁶⁹

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Damaging invasive species that are expected to shift in range because of climate change.

Figure 8.15. Examples of invasive species include the following: (a) Hemlock woolly adelgid, an insect pest, is expected to spread northward with warmer winters and cause die-offs of eastern hemlock trees.¹⁷⁰ (b) Invasive carp are expected to benefit from warmer waters and expand into the Great Lakes, where they will compete with native fishes and present boating hazards through their habit of jumping out of the water.¹⁷¹ (c) Eurasian watermilfoil chokes freshwater systems and outcompetes natives in warmer conditions.¹⁷² (d) European green crabs, which benefit from warmer waters, harm economically important native shellfish fisheries.¹⁷³ Photo credits: (a) Kerry Wixted via Flickr [CC BY-NC 2.0]; (b) Steve Hillebrand, USFWS; (c) ©Stephen K. Hamilton, Cary Institute of Ecosystem Studies; (d) ©P. Sean McDonald, University of Washington.

Assisting Species Adaptation

Natural resource managers are implementing adaptation actions including increasing conservation efforts, reducing habitat fragmentation, protecting wildlife corridors, assisting species migration, and expanding protection activities.¹⁷⁴ For example, marine protected areas can reduce non-climate stressors like overfishing and facilitate recovery of populations following extreme events like heatwaves, which then benefits recreational and commercial fishing in surrounding areas (KM 28.2).¹⁷⁵ Many states now include climate impacts in state wildlife action plans; for example, Massachusetts has identified habitat patches allowing for movement of the threatened Blanding’s turtle and is creating habitats that balance increased drought and other threats.^176,177,178

Managing for connectivity can enhance species climate resilience, particularly for wide-ranging and migratory species.¹⁷⁹ Priorities include connecting climate refugia, areas of high diversity,^123,180 and current and future habitat types.¹⁸¹ For example, resilience strategies for the saltmarsh sparrow (Ammospiza caudacuta), which has declined dramatically due to rising sea levels, include protection of areas expected to convert into future wetlands, use of runnels and other elevation manipulations, and high-marsh restoration.^182,183

Assisted migration has been implemented for at-risk species such as the Laysan albatross, Oʻahu tree snail, relict leopard frog, and wolf (Figure 8.16).¹⁸⁴ In the Chippewa National Forest in Minnesota, seeds of tree species native to red pine forests but collected 100–200 km to the south—and thus genetically distinct from local populations—are being planted to test assisted migration.¹⁸⁵

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Assisted migration can help species adapt to changing climate conditions.

Figure 8.16. One example is the translocation of wolves to Isle Royale National Park, Michigan. The loss of ice bridges in winter prevented new arrivals that would have maintained genetic viability of the population.¹⁸⁶ Photo credit: Jacob W. Frank, NPS.

Implications for Management

While protected areas can help species adapt to climate change, these areas are themselves vulnerable;^{174,187,188,189} many US protected areas are expected to see major shifts in vegetation communities and other species.¹⁹⁰ Further, the existing US protected areas system has low overlap with projected climate refugia;¹⁹¹ extending protection to include future habitat suitability for some species may double costs.¹⁹² Given continued range shifts, areas with priority species that draw tourists (e.g., bird watchers) will need to refocus as some species become rarer or disappear,^193,194 impacting neighboring communities dependent on tourism revenue.

Conflicts (between humans and with wildlife) arising from climate-driven changes in distribution and availability of species and resources are occurring.^195,196 For example, some species are moving out of areas set up to conserve them, and range shifts of fish stocks (including across international boundaries) are causing challenges (KM 10.1).^197,198 Some adaptation policies (e.g., translocation of nonhuman species into human communities unwilling to coexist with them) may exacerbate conflicts (KM 17.2).¹⁹⁹ Adaptive management that prioritizes both climate change response planning and conflict management can reduce negative outcomes.^195,200,201

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Ecosystem services provide substantial and often economically important contributions to communities, ranging from direct material benefits like food production and clean water to nonmaterial benefits like recreation (Figure 8.17). However, economic valuation alone does not reflect intrinsic or relational values that people hold toward nature;^202,203 for example, Tribal and Indigenous Peoples rely on ecosystems for supplies of culturally valuable food, materials for religious ceremonies, and relational links within communities and among generations (KM 16.1).^204,205

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Ecosystems provide a broad range of relational benefits, from the material to the spiritual.

Figure 8.17. Ecosystem services, also called “nature’s contributions to people,” are the benefits that humans receive or derive from ecosystems. These are both material (e.g., energy sources) and non-material (e.g., sense of place), and contribute to the regulation of ecosystem processes. The broad categories of benefits pictured are fluid and overlapping. People value nature in multiple ways, such as “living as” nature (Figure 16.3) or “living from” nature (e.g., people’s dependency on key services). Adapted from O’Connor and Kenter 2019²⁰⁶ [CC BY 4.0].

There are many adverse climate change effects on ecosystem services,^207,208 including reduced water availability for human and agricultural uses (KM 4.1), decreased productivity of crop species due to increased pest infestations (KM 11.1), and losses of hazard-mitigating ecosystems like wetlands and coastal shorelines that provide nursery and nesting habitat, recreation, and aesthetic pleasure (Table 8.2; KM 9.2). However, future trends on ecosystem use and benefits are not always clear. For example, rising temperatures can extend seasonal recreational opportunities, but if daily high temperatures exceed 27°–30°C (80.6°–86°F), recreation tends to decrease.^209,210

Further, diminished benefits from ecosystem services can also occur based on other factors.^211,212 For example, discriminatory planning practices, housing segregation, and racism have created inequitable distributions of services, leading to communities of color experiencing reduced access to benefits like improved air quality or heat reduction (KM 12.2; Figure 12.6).^213,214,215 Lack of access often accompanies other environmental harms (e.g., greater exposure to allergens or risks of green gentrification, the displacement of local residents as environmental benefits improve).^216,217 Climate change is expected to exacerbate these impacts²⁰⁷ and create further difficulties in addressing environmental racism, highlighting the need for clear management priorities and recognition of diverse values.^218,219

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Table 8.2. Examples of Climate Impacts on Ecosystem Services

Climate change affects the availability and quality of many ecosystem services, and many projected impacts on important ecosystem services will also have equity implications.

Ecosystem Service	Potential Climate Impacts	Equity Implications
Regulation of Natural Hazards	Coastal marsh retreat is projected due to sea level rise and increased storm activity.220	Flood risks are often inequitably distributed; for example, property damage risks can be disproportionately higher for Black communities.221
Physical and Psychological Experiences	Cold-weather recreational opportunities are projected to decline (e.g., fewer skiing days).209,210,222	Less green space access in low-income communities and communities of color already results in fewer opportunities for recreation.223,224
Water Quantity	Changes in precipitation, snowpack, soil moisture, and evapotranspiration are projected to alter surface and groundwater availability (KM 4.1; Figure A4.7).	Drought often has disparate impacts;225 for example, Tribal reservations in the US Southwest with higher agricultural dependence will be particularly impacted.226
Regulation of Air Quality	Street trees provide considerable urban air quality benefits but are vulnerable to drought and heat.227	Existing tree canopy distribution is inequitable, accounting for greater air pollution228,229,230 associated with legacies of redlining.231
Food Production (fisheries)	Aquatic systems are experiencing shifts in species ranges, phenologies, distributions, and productivities.232	Culturally important species, such as Chinook salmon for Pacific Northwest Tribes, are projected to dramatically decline in the future.233

Opportunities for Nature-Based Solutions

Ecosystem-based mitigation and adaptation opportunities are often called nature-based solutions (NBSs) or natural climate solutions (Figure 8.18).^234,235 NBSs support biodiversity and can provide other benefits when managed in collaboration with affected communities and use of local knowledge (KM 21.1). For example, coastal wetland restoration provides both mitigation and adaptation benefits by sequestering carbon and decreasing coastal flooding, wave action, and erosion²³⁶ while improving water quality and increasing habitat biodiversity (KM 9.3; Focus on Blue Carbon).²³⁷ NBS projects are often very cost-effective, spurring new financing options.^238,239

Ecosystem-based adaptation is a type of NBS aimed at increasing community resilience to climate change through the use of ecosystems.^240,241 Examples include protecting and restoring floodplains to help reduce flood impacts²⁴² or helping farmers cope with drought through soil conservation measures.²⁴³ There are high returns on investments to restore coastal ecosystems in particular, since US coral reefs provide estimated adaptation benefits of more than $1.8 billion annually (dollar year not provided).^244,245 These approaches can also have positive equity benefits when designed with local participation and buy-in through collaborative approaches (KM 31.4).^{246,247,248,249,250,251}

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Nature-based solutions buffer the effects of climate change.

Figure 8.18. Nature-based solutions (NBS) are actions to protect, manage, and restore ecosystems to address societal challenges such as climate change. Examples in the US include (a) oyster restoration; (b) cover cropping; (c) stormwater management; and (d) urban agriculture. These not only help buffer the impacts of climate change, such as through physical barriers or improved local microclimates, but also provide additional benefits like food and habitat provisioning.^252,253,254 Figure credit: Rutgers University and NPS. See figure metadata for additional contributors. Photo credits: (a) Linda Walters, NPS; (b) David Bosch, USDA; (c) Alisha Goldstein, EPA; (d) Bob Nichols, USDA.

Current and future opportunities for NBSs exist across the US, particularly for mitigation solutions focused on protecting and increasing carbon storage by natural ecosystems (Figures 6.6, 8.19; Focus on Blue Carbon).²⁵⁵ Planning for future protected areas for both climate and biodiversity could emphasize areas that not only hold large amounts of carbon but also help species adapt,²⁵⁶ recognizing the important role that many animal species play in carbon cycling.²⁵⁷ However, NBSs themselves are also vulnerable to rising temperatures, sea level rise, and other climate impacts.²⁵⁸

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Nature-based solutions can support carbon storage while also providing other benefits.

Figure 8.19. Nature-based solutions (NBSs) can preserve or enhance carbon storage in soils and biomass across natural systems like forests, grasslands, and wetlands, as well as agricultural lands. Different approaches vary in their climate mitigation potential, shown here as teragrams of carbon dioxide equivalent (Tg CO₂-eq per year; length of bars) in the year 2025. Lighter green shades indicate the estimated portion of mitigation obtainable for less than $10, $50, or $100 per megagram of CO₂-eq (Mg CO₂-eq). The dark green “Maximum” category shows the highest technical carbon sequestration potential that is also consistent with meeting human needs for food and fiber. Black lines are error bars indicating either the 95% confidence interval or an uncertainty range, depending on the source of the estimate. The arrow indicates a range that may exceed the values shown on the chart. Other potential benefits of NBSs are also indicated for each category (colored dots). Figure addresses contiguous US only. Adapted from Fargione et al. 2018²⁵⁹ [CC BY 4.0].

NBSs that involve restoring degraded ecosystems can improve resilience²⁶⁰ and increase provision of ecosystem services.²⁶¹ Ideally, restoration is designed to recover a range of potential benefits.^262,263 However, multiple services cannot necessarily be maximized simultaneously, as focusing on one ecosystem service at the expense of other benefits leads to trade-offs.^264,265,266 Larger-scale restoration efforts are generally more successful when connected to local priorities,²⁶⁷ including their use in addressing environmental inequities (Box 8.2).²⁶⁸

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