Jay Peterson, National Oceanic and Atmospheric Administration
Douglas Lipton, National Oceanic and Atmospheric Administration
Madeleine A. Rubenstein, U.S. Geological Survey
Sarah R. Weiskopf, U.S. Geological Survey
Lisa Crozier, National Oceanic and Atmospheric Administration
Michael Fogarty, National Oceanic and Atmospheric Administration
Sarah Gaichas, National Oceanic and Atmospheric Administration
Kimberly J. W. Hyde, National Oceanic and Atmospheric Administration
Toni Lyn Morelli, U.S. Geological Survey
Jeffrey Morisette, U.S. Department of the Interior, National Invasive Species Council Secretariat
Hassan Moustahfid, National Oceanic and Atmospheric Administration
Roldan Muñoz, National Oceanic and Atmospheric Administration
Rajendra Poudel, National Oceanic and Atmospheric Administration
Michelle D. Staudinger, U.S. Geological Survey
Charles Stock, National Oceanic and Atmospheric Administration
Laura Thompson, U.S. Geological Survey
Robin Waples, National Oceanic and Atmospheric Administration
Jake F. Weltzin, U.S. Geological Survey
Gregg Marland, Appalachian State University
Matthew Dzaugis, Program Coordinator
Allyza Lustig, Program Coordinator
<b>Lipton</b>, D., M. A. Rubenstein, S.R. Weiskopf, S. Carter, J. Peterson, L. Crozier, M. Fogarty, S. Gaichas, K.J.W. Hyde, T.L. Morelli, J. Morisette, H. Moustahfid, R. Muñoz, R. Poudel, M.D. Staudinger, C. Stock, L. Thompson, R. Waples, and J.F. Weltzin, 2018: Ecosystems, Ecosystem Services, and Biodiversity. In <i>Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II</i> [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 268–321. doi: 10.7930/NCA4.2018.CH7
All life on Earth, including humans, depends on the services that ecosystems provide, including food and materials, protection from extreme events, improved quality of water and air, and a wide range of cultural and aesthetic values. Such services are lost or compromised when the ecosystems that provide them cease to function effectively. Healthy ecosystems have two primary components: the species that live within them, and the interactions among species and between species and their environment. Biodiversity and ecosystem services are intrinsically linked: biodiversity contributes to the processes that underpin ecosystem services; biodiversity can serve as an ecosystem service in and of itself (for example, genetic resources for drug development); and biodiversity constitutes an ecosystem good that is directly valued by humans (for example, appreciation for variety in its own right).3 Significant environmental change, such as climate change, poses risks to species, ecosystems, and the services that humans rely on. Consequently, identifying measures to minimize, cope with, or respond to the negative impacts of climate change is necessary to reduce biodiversity loss and to sustain ecosystem services.4
This chapter focuses on the impacts of climate change at multiple scales: the populations and species of living things that form ecosystems; the properties and processes that support ecosystems; and the ecosystem services that underpin human communities, economies, and well-being. The key messages from NCA3 (Table 7.1) have been strengthened over the last four years by new research and monitoring networks. This chapter builds on the NCA3 findings and specifically emphasizes how climate impacts interact with non-climate stressors to affect ecosystem services. Furthermore, it describes new advances in climate adaptation efforts, as well as the challenges natural resource managers face when seeking to sustain ecosystems or to mitigate climate change (Figure 7.1).
Table 7.1: Key Messages from Third National Climate Assessment
Climate change impacts on ecosystems reduce their ability to improve water quality and regulate water flows.
Climate change, combined with other stressors, is overwhelming the capacity of ecosystems to buffer the impacts from extreme events like fires, floods, and storms.
Landscapes and seascapes are changing rapidly, and species, including many iconic species, may disappear from regions where they have been prevalent or become extinct, altering some regions so much that their mix of plant and animal life will become almost unrecognizable.
Timing of critical biological events, such as spring bud burst, emergence from overwintering, and the start of migrations, has shifted, leading to important impacts on species and habitats.
Whole system management is often more effective than focusing on one species at a time, and can help reduce the harm to wildlife, natural assets, and human well-being that climate disruption might cause.
Table 7.1: Key Messages from the Third National Climate Assessment Ecosystems, Biodiversity, and Ecosystem Services Chapter2
Figure 7.1: Climate Change, Ecosystems, and Ecosystem Services
Figure 7.1: Climate and non-climate stressors interact synergistically on biological diversity, ecosystems, and the services they provide for human well-being. The impact of these stressors can be reduced through the ability of organisms to adapt to changes in their environment, as well as through adaptive management of the resources upon which humans depend. Biodiversity, ecosystems, ecosystem services, and human well-being are interconnected: biodiversity underpins ecosystems, which in turn provide ecosystem services; these services contribute to human well-being. Ecosystem structure and function can also influence the biodiversity in a given area. The use of ecosystem services by humans, and therefore the well-being humans derive from these services, can have feedback effects on ecosystem services, ecosystems, and biodiversity. Sources: NOAA, USGS, and DOI.
There is increasing evidence that climate change is impacting biodiversity, and species and populations are responding in a variety of ways. Individuals may acclimate to new conditions by altering behavioral, physical, or physiological characteristics, or populations may evolve new or altered characteristics that are better suited to their current environment. Additionally, populations may track environmental conditions by moving to new locations. The impacts of climate change on biodiversity have been observed across a range of scales, including at the level of individuals (such as changes in genetics, behavior, physical characteristics, and physiology), populations (such as changes in the timing of life cycle events), and species (such as changes in geographic range).5
Changes in individual characteristics: At an individual level, organisms can adapt to climate change through shifts in behavior, physiology, or physical characteristics.5,6,7,8 These changes have been observed across a range of species in terrestrial, freshwater, and marine systems.5,6,7,8 Some individuals have the ability to immediately alter characteristics in response to new environmental conditions. Behavioral changes, such as changes in foraging, habitat use, or predator avoidance, can provide an early indication of climate change impacts because they are often observable before other impacts are apparent.6
However, some immediate responses to environmental conditions are not transmitted to the next generation. Ultimately, at least some evolutionary response is generally required to accommodate long-term, directional change.9 Although relatively fast evolutionary changes have been documented in the wild,10,11,12 rapid environmental changes can exceed the ability of species to track them.13 Thus, evidence to date suggests that evolution will not fully counteract negative effects of climate change for most species. Importantly, many human-caused stressors, such as habitat loss or fragmentation (Figure 7.2) (see also Ch. 5: Land Changes, “State of the Sector” and KM 2), reduce the abundance as well as the genetic diversity of populations. This in turn compromises the ability of species and populations to cope with additional disturbances.14
Figure 7.2: Genetic Diversity and Climate Exposure
Figure 7.2: Genetic diversity is the fundamental basis of adaptive capacity. Throughout the Pacific Northwest, (a) bull trout genetic diversity is lowest in the same areas where (b) climate exposure is highest; in this case, climate exposure is a combination of maximum temperature and winter flood risk. Sub-regions within the broader Columbia River Basin (shaded gray) represent different watersheds used in the vulnerability analysis. Values are ranked by threat, such that the low genetic diversity and high climate exposure are both considered “high” threats (indicated as red in the color gradient). Source: adapted from Kovach et al. 2015.15
Changes in phenology: The timing of important biological events is known as phenology and is a key indicator of the effects of climate change on ecological communities.16,17,18,19 Many plants and animals use the seasonal cycle of environmental events (such as seasonal temperature transitions, melting ice, and seasonal precipitation patterns) as cues for blooming, reproduction, migration, or hibernation. Across much of the United States, spring is starting earlier in the year relative to 20th-century averages, although in some regions spring onset has been delayed (Figure 7.3) (see also Ch. 1: Overview, Figure 1.2j).20,21,22 In marine and freshwater systems, the transition from winter to spring temperatures23 and the melting of ice24 are occurring earlier in the spring, with significant impacts on the broader ecosystem. Phytoplankton can respond rapidly to such changes, resulting in significant shifts in the timing of phytoplankton blooms and causing cascading food web effects (Ch. 9: Oceans, KM 2).19,24
Figure 7.3: Trends in First Leaf and First Bloom Dates
Figure 7.3: These maps show observed changes in timing of the start of spring over the period 1981–2010, as represented by (top) an index of first leaf date (the average date when leaves first appear on three indicator plants) and (bottom) an index of first bloom date (the average date when blossoms first appear on three indicator plants). Reds and yellows indicate negative values (a trend toward earlier dates of first leaf or bloom); blues denote positive values (a trend toward later dates). Units are days per decade. Indices are derived from models driven by daily minimum and maximum temperature throughout the early portion of the growing season. Source: adapted from Ault et al. 2015.21
One emerging trend is that the rate of phenological change varies across trophic levels (position in a food chain, such as producers and consumers),25,26 resulting in resource mismatches and changes to species interactions. Migratory species are particularly vulnerable to phenological mismatch if their primary food source is not available when they arrive at their feeding grounds or if they lack the flexibility to shift to other food sources.27,28,29
Changes in range: Climate change is resulting in large-scale shifts in the range and abundance of species, which are altering terrestrial, freshwater, and marine ecosystems.2,30,31,32,33 Range shifts reflect changes in the distribution of a population in response to changing environmental conditions and can occur as a result of directional movement or different rates of survival (Ch. 1: Overview, Figure 1.2h). The ability of a species to disperse affects the rate at which species can shift their geographic range in response to climate change and hence is an indicator of adaptive capacity.34 Climate change has led to range contractions in nearly half of studied terrestrial animals and plants in North America; this has generally involved shifts northward or upward in elevation.35 High-elevation species may be more exposed to climate change than previously expected36 and seem particularly affected by range shifts.37 In marine environments, many larval and adult fish have also shown distribution shifts—primarily northward, but also along coastal shelves and to deeper water—that correspond with changing conditions.38
Species vary in the extent to which they track different aspects of climate change (such as temperature and precipitation),39,40,41 which has the potential to cause restructuring of communities across many ecosystems. This variation is increasingly being considered in research efforts in order to improve predictions of species range shifts.42,43,44 Finally, habitat fragmentation and loss of connectivity (due to urbanization, roads, dams, etc.) can prevent species from tracking shifts in their required climate; efforts to retain, restore, or establish climate corridors can, therefore, facilitate movements and range shifts.18,45,46,47
Climate-driven changes in ecosystems derive from the interacting effects of species- and population-level responses, as well as the direct impacts of environmental drivers. Since NCA3, there have been advances in our understanding of several fundamental ecosystem properties and characteristics, including: primary production, which defines the overall capacity of an ecosystem to support life; invasive species; and emergent properties and species interactions. Particular ecosystems that are experiencing specific climate change impacts, such as ocean acidification (Ch. 9: Oceans), sea level rise (Ch. 8: Coastal, KM 2), and wildfire (Ch. 6: Forests, KM 1), can be explored in more detail in sectoral and regional chapters (see also Ch. 1: Overview, Figures 1.2i, 1.2g, and 1.2k).
Changing primary productivity: Almost all life on Earth relies on photosynthetic organisms. These primary producers, such as plants and phytoplankton, are responsible for producing Earth’s oxygen, are the base of most food webs, and are important components of carbon cycling and sequestration. Diverse observations suggest that global terrestrial primary production has increased over the latter 20th and early 21st centuries.48,49,50,51 This change has been attributed to a combination of the fertilizing effect of increasing atmospheric CO2, nutrient additions from human activities, longer growing seasons, and forest regrowth, although the precise contribution of each factor remains unresolved (Ch. 6: Forests, KM 2; Ch. 5: Land Changes, KM 1).50,51,52 Regional trends, however, may differ significantly from global averages. For example, heat waves, drought, insect outbreaks, and forest fires in some U.S. regions have killed millions of trees in recent years (Ch. 6: Forests, KM 1 and 2).
Marine primary production depends on a combination of light, which is prevalent at the ocean’s surface, and nutrients, which are available at greater depths. The separation between surface and deeper ocean layers has grown more pronounced over the past century as surface waters have warmed.53 This has likely increased nutrient limitation in low- and midlatitude oceans. Direct evidence for declines in primary productivity, however, remains mixed.54,55,56,57,58,59,60
Invasive species: Climate change is aiding the spread of invasive species (nonnative organisms whose introduction to a particular ecosystem causes or is likely to cause economic or environmental harm). Invasive species have been recognized as a major driver of biodiversity loss.61,62,63 The worldwide movement of goods and services over the last 200 years has resulted in an increasing rate of introduction of nonnative species globally,64,65 with no sign of slowing.66 Global ecological and economic costs associated with damages caused by nonnative species and their control are substantial (more than $1.4 trillion annually).61 The introduction of invasive species, along with climate-driven range shifts, is creating new species interactions and novel ecological communities, or combinations of species with no historical analog.67,68 Climate change can favor nonnative invading species over native ones.69,70 Extreme weather events aid species invasions by decreasing native communities’ resistance to their establishment and by occasionally putting native species at a competitive disadvantage, although these relationships are complex and warrant further study.71,72,73,74 Climate change can also facilitate species invasions through physiological impacts, such as by increasing per capita reproduction and growth rates.69,75,76
Figure 7.4: Projected Range Expansion of Invasive Lionfish
Figure 7.4: Lionfish, native to the Pacific Ocean, are an invasive species in the Atlantic. Their range is projected to expand closer to (a) the U.S. Atlantic coastline as a result of climate change. The maps show projected range expansion of the invasive lionfish in the southeast United States by mid-century (green) and end of the century (red), based on (b) the lower and (c) higher scenarios (RCP4.5 and RCP8.5, respectively), as compared to their recently observed range (blue). The projected range shifts under a higher scenario (RCP8.5) represents a 45% increase over the current year-round range. Venomous lionfish are opportunistic, generalist predators that consume a wide variety of invertebrates and fishes and may compete with native predatory fishes. Expansion of their range has the potential to increase the number of stings of divers and fishers. Source: adapted from Grieve et al. 2016.77
Changing species interactions and emergent properties: Emergent properties of ecosystems refer to changes in the characteristics, function, or composition of natural communities. This includes changes in the strength and intensity of interactions among species, altered combinations of community members (known as assemblages), novel species interactions, and hybrid or novel ecosystems.78 There is mounting evidence that in some systems (such as plant–insect food webs), higher trophic levels are more sensitive than lower trophic levels to climate-induced changes in temperature, water availability,79,80,81 and extreme events.82 Predator responses to these stressors can lead to higher energetic needs and increased consumption,83 shifts or expansion in seasonal demand on prey resources, or resource mismatches.84,85 Some predators may be able to adapt to changing conditions by switching to alternative or novel food sources86 or adjusting their behavior to forage in cooler habitats to alleviate heat stress.87 Such changes at higher trophic levels directly affect the energetic demands and mortality rates of prey88 and have important impacts on ecosystem functioning, such as biological activity and productivity (as indicated by community respiration rates),89 and on the flow of energy and nutrients within communities and across habitats. For example, in Alaska, brown bears have recently altered their preference for salmon to earlier-ripening berries, changing both salmon mortality rates and the transfer of oceanic nutrients to terrestrial habitats.90 Warming is changing community composition, as species with lower tolerances to disturbance91 and nonoptimal conditions92 are outcompeted. Declining diversity in life histories as a result of climate change is also expected to result in more uniform, less varied population structures, in turn resulting in increased competition and potentially contributing to local extinctions and reduced community resilience.29,93
Lionfish are an invasive species in the Atlantic, and their range is projected to expand closer to …
Increasing evidence since NCA3 demonstrates that climate change continues to affect the availability and delivery of ecosystem services, including changes to provisioning, regulating, cultural, and supporting services. Humans, biodiversity, and ecosystem processes interact with each other dynamically at different temporal and spatial scales.94 Thus, the climate-related changes to ecosystems and biodiversity discussed in this and other chapters of this report all have consequences for numerous ecosystem services. In addition, these climate-related impacts interact with other non-climate stressors, such as pollution, overharvesting, and habitat loss, to produce compounding impacts on ecosystem services.95,96
The adaptive capacity of human communities to deal with these changes will partly determine the magnitude of the resulting impacts to ecosystem services. For example, the shifting range of fish stocks (Ch. 9: Oceans, KM 2), an example of a provisioning ecosystem service, may require vessels to travel further from port, invest in new fishing equipment, or stop fishing altogether; each of these responses implies increasing levels of costs to society.97 A reduction in biodiversity that impacts the abundance of charismatic and aesthetically valuable organisms, such as coral reefs, can lead to a reduction in wildlife-related ecotourism and may result in negative economic consequences for the human communities that rely on them for income.3 Climate change can also impact ecosystem services such as the regulation of climate and air, water, and soil quality.98 Although climate change impacts on ecosystem services will not be uniformly negative, even apparently positive impacts of climate change can result in costly changes. For example, in areas experiencing longer growing seasons (Ch. 10: Ag & Rural, KM 3), farmers would need to shift practices and invest in new infrastructure (Ch. 12: Transportation, KM 1 and 2) in order to fully realize the benefits of these climate-driven changes. Moreover, different human communities and segments of society will be more vulnerable than others based on their ability to adapt; jurisdictional borders, for instance, may limit human migration in response to climate change.99
Oyster reefs exemplify the myriad ways in which ecosystem components support ecosystem services, including water quality regulation, nutrient and carbon sequestration, habitat formation, and shoreline protection. These services are reduced when oyster reefs are impacted by climate change through, for example, sea level rise100,101 and ocean acidification.102 A recent study estimated that the economic value of the non-harvest ecosystem services provided by oyster reefs ranges from around $5,500 to $99,400 (in 2011 dollars) per year per hectare. The value of shoreline protection varied depending on the location but had the highest possible value of up to $86,000 per hectare per year (in 2011 dollars).103 Coral reefs, which provide shoreline protection and support fisheries and recreation, are also threatened by ocean warming and acidification. The loss of recreational benefits associated with coral reefs in the United States is projected to be $140 billion by 2100 (in 2015 dollars) under a higher scenario (RCP8.5) (Ch. 9: Oceans, KM 1).104