finding 8.2 : key-message-8-2

Fisheries, tourism, human health, and public safety depend on healthy coastal ecosystems that are being transformed, degraded, or lost due in part to climate change impacts, particularly sea level rise and higher numbers of extreme weather events (highly likely, high confidence). Restoring and conserving coastal ecosystems and adopting natural and nature-based infrastructure solutions can enhance community and ecosystem resilience to climate change, help to ensure their health and vitality, and decrease both direct and indirect impacts of climate change (likely, high confidence).

This finding is from chapter 8 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

The selection of the author team for the Coastal Effects chapter took into consideration the wide scope and relative sufficiency of the Third National Climate Assessment (NCA3) Coastal chapter. With input and guidance from the NCA4 Federal Steering Committee, the coordinating lead authors made the decision to convene an all-federal employee team with representation from key federal agencies with science, management, and policy expertise in climate-related coastal effects, and to focus the content of the chapter on Key Messages and themes that would both update the work conducted under NCA3 and introduce new themes. For additional information on the author team process and structure, refer to Appendix 1: Process.

A central component of the assessment process was a chapter lead authors’ meeting held in Washington, DC, in May 2017. The Key Messages were initially developed at this meeting. Key vulnerabilities were operationally defined as those challenges that can fundamentally undermine the functioning of human and natural coastal systems. They arise when these systems are highly exposed and sensitive to climate change and (given present or potential future adaptive capacities) insufficiently prepared or able to respond. The vulnerabilities that the team decided to focus on were informed by a review of the existing literature and by ongoing interactions of the author team with coastal managers, planners, and stakeholders. In addition, the author team conducted a thorough review of the technical inputs and associated literature. Chapter development was supported by numerous chapter author technical discussions via teleconference from April to September 2017.

Description of evidence base:

Multiple lines of evidence have determined that coastal environments are critical to support coastal fisheries, tourism, and human health and safety.8be5daa4-2526-49b8-9b71-c9434e436a87,203ed214-e061-4174-8cd1-59646c4ba363,1c31d78a-1b3f-411a-b9d2-751a6f16a460,1e57c93f-53c1-4d66-b5a5-e0aea13f5c5b,a40a8643-379f-46ec-b995-a37a18739fce,3a22fe4f-b6fe-471a-b471-9728b5799689,a9b73f6c-1ffa-45d5-aeb0-376102f00359,49709d7d-c054-4178-886a-98dc337f2cc8,6fe8c24d-3a58-436e-b17b-cedbb4fc788b,c3fc249a-5c15-4573-b6b6-d60dc8209069 These ecosystems are some of the most threatened on the planet and are being transformed, degraded, or destroyed due to climate change (including rising temperatures, rising sea levels, and ocean acidification)76f53dac-696d-49a4-8e5f-94fe037bea6d,b09adbe5-6a17-4d3c-ab96-b3d9e306af67,91134a9b-6dde-4607-bc9f-6301da1e1800,b9c96040-ba9a-4593-bb5b-2ffc9631f595,4a1ded45-a208-40af-a332-51ef369ab244,58155941-4716-4a6a-b5bd-9a945d688d0a and due to other human stressors such as nutrient pollution, habitat and biodiversity loss, and overfishing.

There is growing evidence that one part of the solution to help coastal ecosystems and human communities be more resilient to climate change, including SLR and increasingly intense or frequent storms, is to conserve or restore coastal habitats such as wetlands, beaches and dunes, oyster and coral reefs, and mangroves8be5daa4-2526-49b8-9b71-c9434e436a87,2de0a3fe-b36f-456d-8008-b42605c55fcd,203ed214-e061-4174-8cd1-59646c4ba363,1c31d78a-1b3f-411a-b9d2-751a6f16a460,1e57c93f-53c1-4d66-b5a5-e0aea13f5c5b,a40a8643-379f-46ec-b995-a37a18739fce,3a22fe4f-b6fe-471a-b471-9728b5799689,9bc95c98-f1cf-4836-a3d2-62818bf12166,a9b73f6c-1ffa-45d5-aeb0-376102f00359,49709d7d-c054-4178-886a-98dc337f2cc8,6fe8c24d-3a58-436e-b17b-cedbb4fc788b,e6d4f3b6-089c-4b9e-b1d8-bc023d4f3bac because they help to attenuate waves, decrease wave energy, and reduce erosion.203ed214-e061-4174-8cd1-59646c4ba363 In addition to restoring or protecting natural habitats, there is also a growing interest in, and body of research regarding expectations for, performance in using a combination of natural and built (called hybrid, or nature-based) features, such as living shorelines, to protect coastal communities.1c31d78a-1b3f-411a-b9d2-751a6f16a460,9bc95c98-f1cf-4836-a3d2-62818bf12166,df0fa93a-c5b8-4d54-bdfa-da8976a688d1,88dd8f76-cf2e-4209-a122-23b1a584dd2a,508d9489-5f03-4347-b846-196c064ee7cd,2e094e90-7605-44f0-b473-c26c281d06b8

New information and remaining uncertainties:

The exact amount of coastal habitat loss that is due to climate change versus other human stressors or multiple stressors can be hard to ascertain, because these stressors are all acting simultaneously on coastal habitats. Nevertheless, it is clear that climate change is one of the important stressors impacting coastal habitats and leading to the degradation or loss of these ecosystems, such as the loss of coral habitats to bleaching events due to rising ocean temperatures and the loss of coastal wetlands due to more intense storm events.

The use of natural and nature-based infrastructure (NNBI) to improve coastal resilience is being implemented in many different states (for example, the use of living shorelines is expanding in Maryland, North Carolina, New Jersey, Louisiana, and other states, and the Rebuild by Design competition is implementing a variety of coastal resilience projects in New York and New Jersey), although there remain some uncertainties about how much storm and erosion risk reduction is provided by different techniques or projects and in different settings. The efficacy of NNBI remains uncertain in many instances; comprehensive monitoring, particularly during and after storms, would be required to ascertain how well these features are functioning for protection services. This monitoring could inform future coastal resilience planning and decisions, including the benefits, costs, and/or tradeoffs involved in considering NNBI options.8197f2a0-796a-47b1-869b-5f3492855db4

Assessment of confidence based on evidence:

There is high confidence that coastal ecosystems are particularly vulnerable to climate change. They have already been dramatically altered by human stressors, as documented in extensive and conclusive evidence; additional stresses from climate change point to a growing likelihood of coastal ecosystems being pushed past tipping points from which they will not be able to recover. The overall high confidence is the net result of considering the evidence base, the dramatically altered ecosystems from human stresses, and the directional trend of sea level rise.

References :

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