finding 7.1 : key-message-7-1

Climate change continues to impact species and populations in significant and observable ways (high confidence). Terrestrial, freshwater, and marine organisms are responding to climate change by altering individual characteristics, the timing of biological events, and their geographic ranges (likely, high confidence). Local and global extinctions may occur when climate change outpaces the capacity of species to adapt (likely, high confidence).



This finding is from chapter 7 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

Topics for the chapter were selected to improve the consistency of coverage of the report and to standardize the assessment process for ecosystems and biodiversity. Chapter leads went through the detailed technical input for the Third National Climate Assessment and pulled out key issues that they felt should be updated in the Fourth National Climate Assessment. The chapter leads then came up with an author team with expertise in these selected topics. To ensure that both terrestrial and marine issues were adequately covered, most sections have at least one author with expertise in terrestrial ecosystems and one with expertise in marine ecosystems.

Monthly author calls were held beginning in December 2016, with frequency increasing to every other week as the initial chapter draft deadline approached. During these calls, the team came up with a work plan and fleshed out the scope and content of the chapter. After the outline for the chapter was created, authors reviewed the scientific literature, as well as the technical input that was submitted through the public call. After writing the State of the Sector section, authors pulled out the main findings to craft the Key Messages.

Description of evidence base:

Changes in individual characteristics: Beneficial effects of adaptive capacity depend on adequate genetic diversity within the existing population and sufficient population sizes. In addition, successful adaptive responses require relatively slow or gradual environmental change in relation to the speed of individual or population-level responses.7406884d-2302-4644-aa50-12ed8baf4fd7 Empirical evidence continues to suggest that plastic changes and evolution have occurred in response to recent climate change33aaaa4b-92cf-4bf7-9a3d-a38098c0025d,086f44ae-3443-406b-85a9-ac9c5bc98133,a988867b-3654-4a92-a893-c21abef8fca0,6387ccda-8e18-4d6e-bf85-d2fae8ced001 and may be essential for species’ persistence.e7ad33e8-3837-465b-8225-0ac751706e98,c2e33d71-6daa-415c-bf7d-74ddea5be25e,e73fc163-97ee-4880-b54a-0c4beb2c087f However, adaptation is only possible if genetic diversity has not already been eroded as a result of non-climate related stressors such as habitat loss.f3b02c1c-8314-4f1a-a49e-6eb507e84378 Additionally, projections suggest that climate change may be too rapid for some species to successfully adapt.5f4fd70c-6663-44b9-8dba-8c2a4913bf16,7d11d70a-4bac-469f-ba79-b3b32d3ace45 Adaptive capacity, and by extension the ability to avoid local or even global extinctions, is likely to vary among species and even populations within species.

Changes in range: Shifts in species’ ranges have been documented in both terrestrial and aquatic ecosystems as species respond to climate change.5f4fd70c-6663-44b9-8dba-8c2a4913bf16,71910705-6b0b-4f61-8249-5a2d444ad5fb Approximately 55% of terrestrial and marine plant and animal species studied in temperate North America have experienced range shifts.5f4fd70c-6663-44b9-8dba-8c2a4913bf16 Climate change has led to contractions in the latitudinal or elevational ranges of 41% (97 of 238) of studied terrestrial plant and animal species in North America and Hawaiʻi in the last 50–100 years.5f4fd70c-6663-44b9-8dba-8c2a4913bf16 Range shifts in terrestrial animal communities average 3.8 miles per decade.b0ab019c-3ea7-4e75-986c-2cc74541c187 In marine communities, range shifts of up to 17.4 miles per decade have been documented.53248a09-779c-4d7f-8349-19b7b1a49e5d Planktonic organisms in the water column (that is, passively floating organisms in a body of water) more closely track the trajectory of preferred environmental conditions, resulting in more extensive range shifts; these organisms have exhibited rates of change from 4.3 miles per decade for species with broad environmental tolerances to 61.5 miles per decade for species with low tolerance of environmental change over a 60-year period.4fe22675-e201-4922-a491-9c382d98530c Walsh et al. 2015 0ce13198-a924-4762-bd5c-00519d8ae3fc documented significant changes in the center of distribution over two decades of 43% of planktonic larvae of 45 fish species.

These shifts have been linked to climate velocity—the rate and direction of change in temperature patterns.03aea694-50fe-4d1e-b29e-091adfb0353b,71910705-6b0b-4f61-8249-5a2d444ad5fb,166845d7-e6ca-44b4-a2d5-a3325ed9740d,edbf158f-90c7-48a7-b742-69d76777d51b Marked differences in observed patterns of climate velocity in terrestrial and aquatic ecosystems have been observed.30fe230f-9dc9-41fc-ad29-e584f1244b95,c849fdf7-2cee-4145-ac55-467df10a93b8 Climate velocity in the ocean can be greater than that on land by a factor of seven.53248a09-779c-4d7f-8349-19b7b1a49e5d

Changes in phenology: In marine and freshwater systems, the transition from winter to spring temperatures is occurring earlier in the year, as evidenced by satellite measures of sea surface temperature dating back to 1981.55f15317-d7a2-4ae3-99f1-5e77129d2dfe In addition, the timing of sea ice melt is occurring earlier in the spring at a rate of about 2 days per decade and has advanced by 25–30 days since 1979 in some regions.bf21b6fb-c6f8-431a-82a5-09c4e12fe5f5 Shifts in phenology have been well documented in terrestrial, marine, and freshwater systems.912dbad9-8981-4cb5-8044-eabf0e563dbf As with range shifts, changes to phenology are expected to continue as the climate warms.d0c3b72c-3080-42de-a8e4-dc0edf9d8c56

Extinction risks: The rate and magnitude of climate impacts can exceed the abilities of even the most adaptable species, potentially leading to tipping points and abrupt system changes. In the face of rapid environmental change, species with limited adaptive capacity may experience local extinctions or even global extinctions.3def47b9-0e32-440b-bef1-f9bc176a7dd0,68fcc8c6-b20a-4739-aae6-e98b893d5163

New information and remaining uncertainties:

Changes in individual characteristics: Species and populations everywhere have evolved in response to reigning climate conditions, demonstrating that evolution will be necessary to survive climate change. Nonetheless, there is very limited evidence for evolutionary responses to recent climate change. As reviewed by Crozier and Hutchings 2014,33aaaa4b-92cf-4bf7-9a3d-a38098c0025d only two case studies document evolutionary responses to contemporary climate change in fish, as opposed to plasticity without evolution or preexisting adaptation to local conditions, and both cases involved the timing of annual migration.5ff1aba6-775c-4a18-8b90-055d5119b3c0,df106e89-82b7-4f44-af11-c024e4a47507 In the case of the sockeye salmon, for example, nearly two-thirds of the phenotypic response of an earlier migration date was explained by evolutionary responses rather than individual plastic responses.5ff1aba6-775c-4a18-8b90-055d5119b3c0

Changes in range: Although the evidence for shifting ranges of many terrestrial and aquatic species is compelling, individual species are responding differently to the magnitude and direction of change they are experiencing related to their life history, complex mosaics of microclimate patterns, and climate velocity.6776454b-6265-4ff0-8c4d-9f0463e3c710,e581514a-c053-42e0-8bfd-e53ddc8c3cde,dab231b2-91f6-49ce-9639-a9f9d95169c1,e391be8f-6f56-45c5-804f-e14c09befccb,bbdced6a-1129-4d4e-9fef-215700939ec0 Additionally, projections of future species distributions under climate change are complicated by the interacting effects of multiple components of climate change (such as changing temperature, precipitation, sea level rise, and so on) and effects from non-climate stressors (such as habitat loss and degradation); these multiple drivers of range shifts can have compounding or potentially opposing effects, further complicating projections of where species are likely to be found in the future.9743c446-fef0-44f4-82bd-7f2ff1614205

Assessment of confidence based on evidence:

There is high confidence that species and populations continue to be impacted by climate change in significant and observable ways.

There is high confidence that terrestrial, freshwater, and marine organisms are likely responding to climate change by altering individual characteristics, the timing of biological events, and their geographic ranges.

There is high confidence that local and global extinctions are likely to occur when climate change outpaces the capacity of species to adapt.

References :

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