finding 18.2 : key-message-18-2

The Northeast’s coast and ocean support commerce, tourism, and recreation that are important to the region’s economy and way of life. Warmer ocean temperatures, sea level rise, and ocean acidification (high confidence) threaten these services (likely). The adaptive capacity of marine ecosystems and coastal communities will influence ecological and socioeconomic outcomes as climate risks increase (high confidence).

This finding is from chapter 18 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

It is understood that authors for a regional assessment must have scientific and regional credibility in the topical areas. Each author must also be willing and interested in serving in this capacity. Author selection for the Northeast chapter proceeded as follows:

First, the U.S. Global Change Research Program (USGCRP) released a Call for Public Nominations. Interested scientists were either nominated or self-nominated and their names placed into a database. The concurrent USGCRP Call for Public Nominations also solicited scientists to serve as chapter leads. Both lists were reviewed by the USGCRP with input from the coordinating lead author (CLA) and from the National Climate Assessment (NCA) Steering Committee. All regional chapter lead (CL) authors were selected by the USGCRP at the same time. The CLA and CL then convened to review the author nominations list as a “first cut” in identifying potential chapter authors for this chapter. Using their knowledge of the Northeast’s landscape and challenges, the CLA and CL used the list of national chapter topics that would be most relevant for the region. That topical list was associated with scientific expertise and a subset of the author list.

In the second phase, the CLA and CL used both the list of nominees as well as other scientists from around the region to build an author team that was representative of the Northeast’s geography, institutional affiliation (federal agencies and academic and research institutions), depth of subject matter expertise, and knowledge of selected regional topics. Eleven authors were thus identified by December 2016, and the twelfth author was invited in April 2017 to better represent tribal knowledge in the chapter.

Lastly, the authors were contacted by the CL to determine their level of interest and willingness to serve as experts on the region's topics of water resources, agriculture and natural resources, oceans and marine ecosystems, coastal issues, health, and the built environment and urban issues.

On the due diligence of determining the region’s topical areas of focus

The first two drafts of the Northeast chapter were structured around the themes of water resources, agriculture and natural resources, oceans and marine ecosystems, coastal issues, health, and the built environment and urban issues. During the USGCRP-sponsored Regional Engagement Workshop held in Boston on February 10, 2017, feedback was solicited from approximately 150 online participants (comprising transportation officials, coastal managers, urban planners, city managers, fisheries managers, forest managers, state officials, and others) around the Northeast and other parts of the United States, on both the content of these topical areas and important focal areas for the region. Additional inputs were solicited from other in-person meetings such as the ICNet workshop and American Association of Geographers meetings, both held in April 2017. All feedback was then compiled with the lessons learned from the USGCRP CLA-CL meeting in Washington, DC, also held in April 2017. On April 28, 2017, the author team met in Burlington, Vermont, and reworked the chapter’s structure around the risk-based framing of interest to 1) changing seasonality, 2) coastal/ocean resources, 3) rural communities and livelihoods, 4) urban interconnectedness, and 5) adaptation.

Description of evidence base:

Warming rates on the Northeast Shelf have been higher than experienced in other ocean regions,fb1f46cd-8b70-4a44-923a-66df61ffa0be and climate projections indicate that warming in this region will continue to exceed rates expected in other ocean regions.f44f9474-6d98-43a9-8d7f-ee808ecaf41e,0826d3d5-2742-415f-a9de-3621c4b79442 Multiple lines of research have shown that changes in ocean temperatures and acidification have resulted in distribution,8b09bbe8-9f42-412e-a4d6-ef4889f56556,71910705-6b0b-4f61-8249-5a2d444ad5fb,8576d351-1b18-4e20-a651-4ab791c17b51 productivity,fb1f46cd-8b70-4a44-923a-66df61ffa0be,e38a7ce3-351a-4c6b-8afe-b9080f69582e,867d1e64-e364-496c-9e0c-1593182bb40d,6d463f21-0ac9-48a2-a86b-41a4b46d8a95 and phenology shifts1dfd2171-2be3-40b2-a8e2-c0df84ec462a,ee25e7ff-68f2-4935-81d9-b012b0aa88c5,321b9ab8-573b-4f45-989d-8d1c978c7626,0ce13198-a924-4762-bd5c-00519d8ae3fc,18e57808-1999-4c24-911d-abce180ac68b in marine populations. These shifts have impacted marine fisheries and prompted industry adaptations to changes.1dfd2171-2be3-40b2-a8e2-c0df84ec462a,f147452b-e846-4fdd-aad9-3110322e071c,e26419d1-d4f6-49ff-bf8a-352478b39cce

Research also shows that sea level rise has beenb58704d1-b4ec-46d0-9dd5-e7573523951e,480ff362-8434-4861-a8bb-2dc6615bdcdc,70b9fb1f-c611-4bb7-ad28-ea752489a5de,df484606-34bd-40f9-b6f7-55980a18a737 and will be higher in the Northeast with respect to the rest of the United Statesb58704d1-b4ec-46d0-9dd5-e7573523951e,0e116266-7679-409f-b1d6-99c31edfcd9e,9d9fd9a7-2def-4cf2-8e2e-2c23423f0a6e,38924fa0-a0dd-44c9-a2a0-366ca610b280 due largely to vertical land movement,a26008f1-a98f-45f7-b964-9dda3dee8a0c,fe939844-ef16-412c-afe6-42017bad20d5,10fe1f35-74b2-4636-a0b0-a1f85879367e varying atmospheric shifts and ocean dynamics,199b0e91-24ab-429c-ab3f-1930b96c62a0,143752b0-3899-41fe-963b-5b040305a5be,1724fddf-0454-4565-a66e-bf17d47a48ce,c02e02f3-5a54-40ab-9f09-76e98edcbd48,18a2427b-fb63-48b1-8b74-fd476a4cac1f,9a5f3738-4283-4df2-adb6-8a0cac785d22 and ice mass loss from the polar regions.4531ff9e-d432-4564-9b72-2d334532ceb8 High tide flooding has increased91aeffdb-e82f-4645-abe9-f6ea6909e979,048006a1-a72d-44a1-bdab-fff317c842f7 and will continue to increase,bbf3043e-9999-4f0e-8d0c-6012450d9d84 and storm surges due to stronger and more frequent hurricanes75cf1c0b-cc62-4ca4-96a7-082afdfe2ab1,30f063e3-4595-4c30-8fc2-917b12b7dca6,52ce1b63-1b04-4728-9f1b-daee39af665e have been and will be amplified by sea level rise.b072d10e-db78-421e-a708-e2bdcb25de6e,be9c98a9-915f-4d78-80b9-239b70f93ae2,728f4919-d8c6-4749-968e-18a16550540b,493e26f3-3374-43b9-ad00-f6581ac6877b Climate-related coastal impacts on the landscape include greater potential for coastal flooding, erosion, overwash, barrier island breaching and disaggregation, and marsh conversion to open water,b58704d1-b4ec-46d0-9dd5-e7573523951e,91aeffdb-e82f-4645-abe9-f6ea6909e979,97387e44-8bfc-413a-948c-e6dc67f5e7cd,15451c8d-0add-40c7-a7e6-c286ccbf76f6,8de8f6f9-4357-4630-afd5-a6ea5c79d25a,f42ac321-5f3f-4222-a273-b2064a727ffb,1ddd36b9-851b-48ac-a9f6-b5fee00fa092,3dfa60a1-5063-41e1-80c7-c202d68fef32,1afa6fa0-959e-4b0e-a327-5feb744293a4,a2887179-dcd1-4831-b274-035f4699f859,afaa45d6-8934-47ad-b69e-e1567f1217fc which will directly affect the ability of ecosystems to sustain many of the services they provide. Changes to salt marshes in response to sea level rise have already been observed in some coastal settings in the region, although their impacts are site specific and variable.feb05a46-1a26-4007-85d7-d455699e651d,10d8123f-e4c0-402a-98bd-84e2a156686b,86496fac-2211-4e7b-a8a5-52d45f9b787a,cf22595d-dd65-41de-9be2-d2a7d8e32f94,e5dd9ecb-4526-4d23-b960-6b4b34ea3a38,194da562-dd7c-41d3-a540-e2e9b8a35ecb,2ffdedca-017c-4411-b7f9-7f7c3ad0baa8,e8b4d6de-985b-41cc-b1ad-5051c39f6ee9 Studies quantifying sea level rise impacts on other types of coastal settings (such as beaches) in the region are more limited; however, there is consensus on what impacts under higher rates of relative sea level rise might look like due to geologic history and modern analogs elsewhere (such as the Louisiana coast).b58704d1-b4ec-46d0-9dd5-e7573523951e,15451c8d-0add-40c7-a7e6-c286ccbf76f6,afaa45d6-8934-47ad-b69e-e1567f1217fc Although probabilistically low, worst-case sea level rise projections that account for ice sheet collapsec66bf5a9-a6d7-4043-ad99-db0ae6ae562c,8e8cff98-5658-4597-8fb4-9088556acfae would result in sea level rise rates far beyond the rates at which natural systems are likely able to adapt,f4de2290-29cf-421e-b520-55e3e2fbde02,4071d07b-0079-4055-abaa-71db3428a613,0fe018b1-0ae5-4480-a662-0d2c1d6ee5ee affecting not only ecosystems function and services but also likely substantially changing the coastal landscape largely through inundation.97387e44-8bfc-413a-948c-e6dc67f5e7cd

New information and remaining uncertainties:

Although work to value coastal and marine ecosystems services is still evolving,874f9406-dd99-4e92-b64a-4542c23d0d16,8be5daa4-2526-49b8-9b71-c9434e436a87,512ea1ca-1e76-4c71-9ba7-97eac0140255 changes to coastal ecosystem services will depend largely on the adaptability of the coastal landscape, direct hits from storms, and rate of sea level rise, which have identified uncertainties. Lower sea level rise rates are more probable, though the timing of ice sheet collapseae82c8a3-3033-4103-91e9-926a27d1fa18 and the variability of ocean dynamics are still not well understood199b0e91-24ab-429c-ab3f-1930b96c62a0,143752b0-3899-41fe-963b-5b040305a5be,18a2427b-fb63-48b1-8b74-fd476a4cac1f and will dramatically affect the rate of rise.c66bf5a9-a6d7-4043-ad99-db0ae6ae562c,8e8cff98-5658-4597-8fb4-9088556acfae It is also difficult to anticipate how humans will contend with changes along the coast7e02aaef-bbc5-4d00-a53e-31ee9e8095f6 and how adjacent natural settings will respond. Furthermore, specific tipping points for many coastal ecosystems are still not well resolved4071d07b-0079-4055-abaa-71db3428a613,0702b6c9-25a7-4185-a48d-c0b5579275b6,0fe018b1-0ae5-4480-a662-0d2c1d6ee5ee and vary due to site-specific conditions5fde38f4-be63-40ce-88fa-392a869e7c88,f4de2290-29cf-421e-b520-55e3e2fbde02

The Northeast Shelf is sensitive to ocean acidification, and many fisheries in the region are dependent on shell-forming organisms.07043123-9da3-43da-a9fa-36885cd77331,713bb290-1c8c-4d9a-8b65-3941399b48b9,0b185997-744b-4272-9381-d7b94a26d7e2 However, few studies that have investigated the impacts of ocean acidification on species biology and ecology used native populations from the region713bb290-1c8c-4d9a-8b65-3941399b48b9 or tested the effects at acidification levels expected over the next 20–40 years.7da52043-249d-4413-9e1a-40ed0659b2f8 Moreover, there are limited studies that consider the effects of climate change in conjunction with multiple other stressors that affect marine populations.fb1f46cd-8b70-4a44-923a-66df61ffa0be,fda5d878-d7b2-48d9-a2c4-bb0721262ce5,ad9cbd45-a115-4a2a-9e9f-9ed17a171a8b,9affa7ba-ae75-479d-9288-d3cfa29ed5f4 Limited understanding of the adaptive capacity of species to environmental changes presents major uncertainties in ecosystem responses to climate change.7da52043-249d-4413-9e1a-40ed0659b2f8,e3806275-d9a5-4c0a-9e20-7acda7390db6 How humans will respond to changes in ecosystems is also not well known, yet these decisions will shape how marine industries and coastal communities are affected by climate change.548bc141-7fd7-45bb-9c1b-e2a25bcb4e24

Assessment of confidence based on evidence:

Warming ocean temperatures (high confidence), acidification (high confidence), and sea level rise (very high confidence) will alter coastal and ocean ecosystems (likely) and threaten the ecosystems services provided by the coasts and oceans (likely) in the Northeast. There is high confidence that ocean temperatures have caused shifts in the distribution, productivity, and phenology of marine species and very high confidence that high tide flooding and storm surge impacts are being amplified by sea level rise. Because much will depend on how humans choose to address or adapt to these problems, and as there is considerable uncertainty over the extent to which many of these coastal systems will be able to adapt, there is medium confidence in the level of risk to traditions and livelihoods. It is likely that under higher scenarios, sea level rise will significantly alter the coastal landscape, and rising temperatures and acidification will affect marine populations and fisheries.

References :

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