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Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities

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... Sea level rise was not mentioned as a reason for coastal armouring by the interviewed islanders, although it is perceived as an existential threat in many other atolls of the Pacific (Donner and Webber 2014; Teaiwa 2019). However, the sea level is predicted to rise by 0.43 to 0.84 cm by 2100 (Oppenheimer et al. 2019). Most constructions, notably on the Rangiroa atoll but also in all the coastal zones of the volcanic islands, are not sufficiently high relative to the sea to avoid submersion during storms in the short term (about half of the houses are located in zones that have been submersed at least once since the 1980s on Rangiroa; Magnan et al. 2019) and due to sea level rise in the longer term. ...
... Overall, this study contributes to a growing pool of knowledge about human disturbances of the coastline in French Polynesia. It constitutes a baseline to communicate with the public and promote sustainable coastal management so that decision-makers on French Polynesian islands can make informed decisions in the face of climate changeinduced cyclones and storms, sea level rise (with drastic implications for lifestyles within a few decades), and loss of biodiversity (Oppenheimer et al. 2019;IPCC 2021). Springer Nature journal content, brought to you courtesy of Springer Nature Customer Service Center GmbH ("Springer Nature"). ...
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Coastal urbanisation is not constrained only to heavily industrialised cities. It has reached the coastlines of French Polynesia islands (South Pacific). In the context of climate change–induced cyclones and storms, sea level rise, and ecosystem damage, characterising the evolution and current extent of man-made structures along coastlines is of key importance for managers. In French Polynesia, three high volcanic islands (Taha’a, Raiatea, Maupiti) and one atoll (Rangiroa) were selected as case studies to highlight the increasing extent of artificial coastal structures in a tropical setting. Using high-resolution aerial imagery from the mid-twentieth century and from recent years, changes in coastal typology were assessed. The proportion of natural coastlines decreased from over 90% to under 40% within seven decades on the volcanic islands, mostly due to a boom in private embankments. This decrease was more limited in Rangiroa (93 to 89%), possibly due to its different morphological characteristics and coastal protection requirements. Based on these changes, for more sustainable management of island coasts, we recommend adopting case-by-case policies to rectify past and current management and urban planning strategies, especially relating to private embankments.
... Therefore, this historical activity is considered intangible cultural heritage since it represents distinct social practices, rituals, festive events, oral traditions and expressions, and also, knowledge and practices concerning traditional craftsmanship and nature (UNESCO, 2018). In face of the climatic changes, with extreme consequences on coastal areas (Oppenheimer & Glavovic, 2019) the traditional ecological knowledge held by coastal populations is very important to contribute on mitigation and adaptation processes (Freitas et al. 2018). As far as the environment is concerned, since the UNESCO 1972 "Convention for the Protection of the World Cultural and Natural Heritage" that the broad concept of cultural heritage encompasses environmental assets along with historical, artistic and archaeological ones (UNESCO, 1973). ...
... This study focuses on a geologically short, but critical, time span similar to the Intergovernmental Panel on Climate Change climate projections (Oppenheimer et al., 2019). However there are implications from this work that can be extended to longer time horizons. ...
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Climate change is raising sea levels across the globe. On river deltas, sea‐level rise (SLR) may result in land loss, saline intrusion into groundwater aquifers, and other problems that adversely impact coastal communities. There is significant uncertainty surrounding future SLR trajectories and magnitudes, even over decadal timescales. Given this uncertainty, numerical modeling is needed to explore how different SLR projections may impact river delta evolution. In this work, we apply the pyDeltaRCM numerical model to simulate 350 years of deltaic evolution under three different SLR trajectories: steady rise, an abrupt change in SLR rate, and a gradual acceleration of SLR. For each SLR trajectory, we test a set of six final SLR magnitudes between 5 and 40 mm/yr, in addition to control runs with no SLR. We find that both surface channel dynamics as well as aspects of the subsurface change in response to higher rates of SLR, even over centennial timescales. In particular, increased channel mobility due to SLR corresponds to higher sand connectivity in the subsurface. Both the trajectory and magnitude of SLR change influence the evolution of the delta surface, which in turn modifies the structure of the subsurface. We identify correlations between surface and subsurface properties, and find that inferences of subsurface structure from the current surface configuration should be limited to time spans over which the sea level forcing is approximately steady. As a result, this work improves our ability to predict future delta evolution and subsurface connectivity as sea levels continue to rise.
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Observational data from satellite altimetry were used to quantify the performance of CMIP6 models in simulating the climatological mean and interannual variance of the dynamic sea level (DSL) over 40°S–40°N. In terms of the mean state, the models generally agree well with observations, and high consistency is apparent across different models. The largest bias and model discrepancy is located in the subtropical North Atlantic. As for simulation of the interannual variance, good agreement can be seen across different models, yet the models present a relatively low agreement with observations. The simulations show much weaker variance than observed, and bias is apparent over the subtropics in association with strong western boundary currents. This nearshore bias is reduced considerably in HighResMIP models. The underestimation of DSL interannual variance is at least partially due to the misrepresentation of ocean processes in the CMIP6 historical simulation with its relatively low resolution. The results identify directions for future model development towards a better understanding of the mean and interannual variability of DSL. 摘要 本研究采用卫星测高数据与第六次国际耦合模式比较计划 (CMIP6) 进行对比, 重点针对40°S–40°N地区的动力海平面 (DSL) , 评估了模式对其平均态与年际变率的综合模拟能力.结果表明, 对于DSL平均态的模拟, 模式与观测结果非常吻合, 模式之间的差异较小, 其中, 副热带北大西洋是模拟偏差和模式间差异较为显著的区域.对于DSL年际变率的模拟, 模式之间保持较高的一致性, 但是, 模式与观测结果存在明显差异, 模式普遍低估了DSL的年际方差, 其中, 误差大值区域出现在副热带西边界流附近.模式分辨率会影响CMIP6对中小尺度海洋过程的重现能力, 这可能是导致CMIP6历史模拟出现误差的原因之一.
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Coastal restoration is often distrusted and, at best, implemented at small scales, which hampers its potential for coastal adaptation. Present technical, economic and management barriers stem from sectoral and poorly coordinated local interventions, which are insufficiently monitored and maintained, precluding the upscaling required to build up confidence in ecosystem restoration. The paper posits that there is enough knowledge, technology, financial and governance capabilities for increasing the pace and scale of restoration, before the onset of irreversible coastal degradation. We propose a systemic restoration, which integrates Nature based Solutions (NbS) building blocks, to provide climate-resilient ecosystem services and improved biodiversity to curb coastal degradation. The result should be a reduction of coastal risks from a decarbonised coastal protection, which at the same time increases coastal blue carbon. We discuss barriers and enablers for coastal adaptation-through-restoration plans, based on vulnerable coastal archetypes, such as deltas, estuaries, lagoons and coastal bays. These plans, based on connectivity and accommodation space, result in enhanced resilience and biodiversity under increasing climatic and human pressures. The paper concludes with a review of the interconnections between the technical, financial and governance dimensions of restoration, and discusses how to fill the present implementation gap.
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„Waste Land 2046 – We told you so“ zeichnet ein dystopisches Zukunftsszenario in dem es sowohl global wie auch in Deutschland zu massiven ökologischen und gesellschaftlichen Umwälzungen kommt. Dieses Szenario zeichnet sich durch einen rasant voranschreitenden Klimawandel aus, wodurch Ökosysteme in ganz Deutschland kollabieren und die Versorgung mit Nahrungsmitteln, Produktionsgütern sowie Energie immer volatiler wird. Diese dystopischen Entwicklungen werden untermauert durch ein Auseinanderdriften der Gesellschaft. In Bochum separieren sich wohlhabende Bevölkerungsschichten von den Leidtragenden der direkten und indirekten Klimafolgen. Dies mündet in einer breiten Lethargie der Bevölkerung, die durch eine Stadtverwaltung im ständigen Krisenmodus untermauert wird. Finanzielle Mittel reichen aus, um teilweise die Grundversorgung zu gewährleisten, für zukunftsweisende Veränderungen fehlen in allen Bereichen ökonomische und gesellschaftliche Kapazitäten.
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Arguing that ‘the moment of the now’ calls for fresh, creative thinking in the search for solutions, this White Paper both explores the state of research at the intersection between culture, heritage and climate change, and makes a case for a set of approaches, perspectives and conversations that we need to have—or that we need to have in new ways. Taking a broad view of heritage as ‘the archive of accumulated human wisdom’, it explores both small-s solutions (immediate, techno-infrastructural fixes) and big-S Solutions (changes in values, behaviours and worldviews). First, it defines a ‘heritage perspective’ on climate change via four attributes: an orientation towards deep time; an orientation towards the future; an orientation towards local and Indigenous knowledge; and an orientation towards both practice and critical thinking. Then it presents a review of the relevant scientific and scholarly literatures, according to the scoping questions. Next, it presents eight heritage-focused case studies, each of which orients us towards solutions to the challenges of anthropogenic climate change. We need to consider an encompassing view of heritage, that draws from both the fields of heritage studies and heritage management. The archive of local and Indigenous knowledge and practice offers many potential solutions, but raises key questions around ethics, intellectual property and terms of engagement. Climate change itself needs to be understood as an historically situated phenomenon, that has involved and implicated populations and territories differently, especially across the Global North/ Global South divide. Recognizing this, it becomes imperative to foreground a climate justice perspective in the search for solutions. Experience suggests that science-based solutions are likely to be socially, economically, politically and culturally entangled. Social science and humanities-based approaches play a key role in allowing us to anticipate and understand such entanglements. Rather than being static and backward-looking, heritage is mobile, forward-looking and always in-the-making. Mobilising the affective power of heritage becomes a potentially powerful tool in organising for climate action—although this involves emphasising a different version of heritage, less concerned with national pasts and more with collective human endeavour. The creative arts play a key role in imagining viable futures, and in producing resonance, ‘believe-ability’ and hope. The political struggle around the climate emergency is the struggle for multilateralism, dialogue and cooperation, in the face of populist attempts to use a moment of historical anxiety for narrowly sectarian ends. From a heritage perspective, the question of relevance is: How do we mobilise the affective power of heritage in support of open, creative, and inclusive futures?
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Heightened recognition of impacts to coastal salt marshes from sea-level rise has led to expanding interest in using thin-layer sediment placement (TLP) as an adaptation tool to enhance future marsh resilience. Building on successes and lessons learned from the Gulf and southeast U.S. coasts, projects are now underway in other regions, including New England where the effects of TLP on marsh ecosystems and processes are less clear. In this study, we report on early responses of a drowning, microtidal Rhode Island marsh (Ninigret Marsh, Charlestown, RI) to the application of a thick (10–48 cm) application of sandy dredged material and complimentary extensive adaptive management to quickly build elevation capital and enhance declining high marsh plant species. Physical changes occurred quickly. Elevation capital, rates of marsh elevation gain, and soil drainage all increased, while surface inundation, die-off areas, and surface ponding were greatly reduced. Much of the marsh revegetated within a few years, exhibiting aspects of classic successional processes leading to new expansive areas of high marsh species, although low marsh Spartina alterniflora recovered more slowly. Faunal communities, including nekton and birds, were largely unaffected by sediment placement. Overall, sediment placement provided Ninigret Marsh with an estimated 67–320 years of ambient elevation gain, increasing its resilience and likely long-term persistence. Project stakeholders intentionally aimed for the upper end of high marsh plant elevation growth ranges to build elevation capital and minimize maintenance costs, which also resulted in new migration corridors, providing pathways for future marsh expansion.
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We present a historical record of landfalling tropical cyclones (TCs, 85 events) over the Mascarene Islands (southern Indian Ocean) since the 17th century to evaluate interannual-to-decadal-scale changes in past TC variability, from the cooler Little Ice Age (LIA) to the present warming world, and to contextualize present and future changes in risk estimates. For the Mascarene Islands, we observe a mean fourfold increase in regional landfalling TCs, beginning around 1940. Before this date, the historical TC data exhibit clear decadal cycles, which mirror solar radiative forcing. This historical record demonstrates how enhanced understanding of past variability can improve baseline risk estimates of TCs making landfall in the SW Indian Ocean basin.
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