Regionalisation of population growth projections in coastal exposure analysis

Large-area coastal exposure and impact analysis has focussed on using sea-level rise (SLR) scenarios and has placed little emphasis on ocioeconomic scenarios, while neglecting spatial variations of population dynamics. We use the Dynamic Interactive Vulnerability Assessment (DIVA) Framework to assess the population exposed to 1 in 100-year coastal flood events under different population scenarios, that are onsistent with the shared socioeconomic pathways (SSPs); and different SLR scenarios, derived from the representative concentration pathways (RCPs); and analyse the effect of accounting for regionalised population dynamics on population exposure until 2100. In a reference approach, we use homogeneous population growth on national level. In the regionalisation approaches, we test existing spatially explicit projections that also account for urbanisation, coastal migration and urban sprawl. Our results show that projected global exposure in 2100 ranges from 100 million to 260 million, depending on the combination of SLR and population scenarios and method used for regionalising the population projections. The assessed exposure based on the regionalised approaches is higher than that derived from the reference approach by up to 60 million people (39%). Accounting for urbanisation and coastal migration leads to an increase in exposure, whereas considering urban sprawl leads to lower exposure. Differences between the reference and the regionalised approaches increase with higher SLR. The regionalised approaches show highest exposure under SSP5 over most of the twenty-first century, although total population in SP5 is the second lowest overall. All methods project the largest absolute growth in exposure for Asia and relative growth for Africa

Actualised and future changes in regional economic growth through sea level rise

This study investigates the long-term economic impact of sea-level rise (SLR) on coastal regions in Europe, focusing on Gross Domestic Product (GDP). Using a novel dataset covering regional SLR and economic growth from 1900 to 2020, we quantify the relationships between SLR and regional GDP per capita across 79 coastal EU & UK regions. Our results reveal that the current SLR has already negatively influenced GDP of coastal regions, leading to a cumulative 4.7% loss at 39 cm of SLR. Over the 120 year period studied, the actualised impact of SLR on the annual growth rate is between -0.02% and 0.04%. Extrapolating these findings to future climate and socio-economic scenarios, we show that in the absence of additional adaptation measures, GDP losses by 2100 could range between -6.3% and -20.8% under the most extreme SLR scenario (SSP5-RCP8.5 High-end Ice, or -4.0% to -14.1% in SSP5-RCP8.5 High Ice). This statistical analysis utilising a century-long dataset, provides an empirical foundation for designing region-specific climate adaptation strategies to mitigate economic damages caused by SLR. Our evidence supports the argument for strategically relocating assets and establishing coastal setback zones when it is economically preferable and socially agreeable, given that protection investments have an economic impact

Synthesis, Crystal Structure, and Solid-State NMR Investigations of Heteronuclear Zn/Co Coordination Networks - A Comparative Study

Synthesis and solid-state NMR characterization of two isomorphous series of zinc and cobalt coordination networks with 1,2,4-triazolyl benzoate ligands are reported. Both series consist of 3D diamondoid networks with four-fold interpenetration. Solid-state NMR identifies the metal coordination of the ligands, and assignment of all 1H and 13C shifts was enabled by the combination of 13C editing, FSLG-HETCOR spectra, and 2D 1H–1H back-to-back (BABA) spectra with results from NMR-CASTEP calculations. The incorporation of Co2+ replacing Zn2+ ions in the MOF over the full range of concentrations has significant influences on the NMR spectra. A uniform distribution of metal ions is documented based on the analysis of 1H T1 relaxation time measurements

Global coastal wetland change under sea-level rise and related stresses: The DIVA Wetland Change Model

The Dynamic Interactive Vulnerability Assessment Wetland Change Model (DIVA_WCM) comprises a dataset of contemporary global coastal wetland stocks (estimated at 756 × 10^3 km^2 (in 2011)), mapped to a one-dimensional global database, and a model of the macro-scale controls on wetland response to sea-level rise. Three key drivers of wetland response to sea-level rise are considered: 1) rate of sea-level rise relative to tidal range; 2) lateral accommodation space; and 3) sediment supply. The model is tuned by expert knowledge, parameterised with quantitative data where possible, and validated against mapping associated with two large-scale mangrove and saltmarsh vulnerability studies. It is applied across 12,148 coastal segments (mean length 85 km) to the year 2100. The model provides better-informed macro-scale projections of likely patterns of future coastal wetland losses across a range of sea-level rise scenarios and varying assumptions about the construction of coastal dikes to prevent sea flooding (as dikes limit lateral accommodation space and cause coastal squeeze). With 50 cm of sea-level rise by 2100, the model predicts a loss of 46–59% of global coastal wetland stocks. A global coastal wetland loss of 78% is estimated under high sea-level rise (110 cm by 2100) accompanied by maximum dike construction. The primary driver for high vulnerability of coastal wetlands to sea-level rise is coastal squeeze, a consequence of long-term coastal protection strategies. Under low sea-level rise (29 cm by 2100) losses do not exceed ca. 50% of the total stock, even for the same adverse dike construction assumptions. The model results confirm that the widespread paradigm that wetlands subject to a micro-tidal regime are likely to be more vulnerable to loss than macro-tidal environments. Countering these potential losses will require both climate mitigation (a global response) to minimise sea-level rise and maximisation of accommodation space and sediment supply (a regional response) on low-lying coasts.The authors gratefully acknowledge funding from the European Union under contract number EVK2-2000-22024. They thank all their partners in the DINAS-COAST project Dynamic and Interactive Assessment of National, Regional and Global Vulnerability of Coastal Zones to Climate Change and Sea-level rise. We are grateful to staff at UNEP-WCMC for generous access to evolving databases on global coastal wetland extent: Jon Hutton, Hannah Thomas, Jan-Willem van Bochove, Simon Blyth and Chris McOwen. Current wetland databases held at WCMC build upon the pioneering efforts of Mark Spalding and Carmen Lacambra.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.gloplacha.2015.12.01

Understanding the drivers of coastal flood exposure and risk from 1860 to 2100

Global coastal flood exposure (population and assets) has been growing since the beginning of the industrial age and is likely to continue to grow through 21st century. Three main drivers are responsible: (1) climate-related mean sea-level change, (2) vertical land movement contributing to relative sea-level rise, and (3) socio-economic development. This paper attributes growing coastal exposure and flood risk from 1860 to 2100 to these three drivers. For historic flood exposure (1860 to 2005) we find that the roughly six-fold increase in population exposure and 53-fold increase in asset exposure are almost completely explained by socio-economic development (>97% for population and >99% for assets). For future exposure (2005 to 2100), assuming a middle-of-the-road regionalized socio-economic scenario (SSP2) without coastal migration and sea-level rise according to RCP2.6 and RCP6.0, climate-change induced sea-level rise will become the most important driver for the growth in population exposure, while growth in asset exposure will still be mainly determined by socio-economic development

Fiscal effects and the potential implications on economic growth of sea level rise impacts and coastal zone protection

Climate change impacts on coastal zones could be significant unless adaptation is undertaken. One particular macro-economic dimension of sea level rise (SLR) impacts that has received no attention so far is the potential stress of SLR impacts on public budgets. Adaptation will require increased public expenditure to protect assets at risk and could put additional stress on public budgets. We analyse the macroeconomic effects of SLR adaptation and impacts on public budgets. We include fiscal indicators in a climate change impact assessment focusing on SLR impacts and adaptation costs using a computable general equilibrium model extended with a detailed description of the public sector. Coastal protection expenditure is financed issuing government bonds, meaning that coastal adaptation places an additional burden on public budgets. SLR impacts are examined using several scenarios linked to three different Representative Concentration Pathways: 2.6, 4.5 and 8.5, and two Shared Socio-economic Pathways: SSP2 and SSP5. Future projections of direct damages of mean and extreme SLR and adaptation costs are generated by the Dynamic Interactive Vulnerability Assessment framework. Without adaptation, all world regions suffer a loss and public deficits increase respect to the reference scenario. Higher deficits imply higher government borrowing from household savings reducing available resources for private investments therefore decreasing capital accumulation and growth. Adaptation benefits result from two mechanisms: i) the avoided direct impacts, and ii) a reduced public deficit effect. This allows for an increased capital accumulation, suggesting that support to adaptation in deficit spending might trigger positive effects on public finance sustainability

A global analysis of subsidence, relative sea-level change and coastal flood exposure

Climate-induced sea-level rise and vertical land movements, including natural and humaninduced subsidence in sedimentary coastal lowlands, combine to change relative sea levels around the world's coast. Although this affects local rates of sea-level rise, assessments of the coastal impacts of subsidence are lacking on a global scale. Here, we quantify global-mean relative sea-level rise to be 2.5 mm/yr over the last two decades. However, as coastal inhabitants are preferentially located in subsiding locations, they experience an average relative sea-level rise up to four times faster at 7.8 to 9.9 mm/yr. These results indicate that the impacts and adaptation needs are much higher than reported global sea-level rise measurements suggest. In particular, human-induced subsidence in and surrounding coastal cities can be rapidly reduced with appropriate policy for groundwater utilization and drainage. Such policy would offer substantial and rapid benefits to reduce growth of coastal flood exposure due to relative sea-level rise

Reply to “Global coastal wetland expansion under accelerated sea-level rise is unlikely”

We thank Törnqvist et al. for engaging with our modelling study on the future response of global coastal wetlands to sea-level rise (SLR) and their careful and critical discussion of the presented methods and results. However, we disagree with their suggestion that our modelling approach is inadequate, a claim which relies on two arguments: (1) they argue that our results are inconsistent with the “A/S (accommodation versus sediment supply) theory”; (2) they refer to coastal Louisiana as a case example where our modelling results would deviate from historic observations and future projections of coastal wetland change. However, below we will demonstrate that Törnqvist et al.’s application of the A/S theory is not valid to predict changes in coastal wetland area, and that our global predictions are in line with regional observations and projections for coastal Louisiana and the wider region of the Gulf of Mexico. Taking coastal Louisiana as an example, Törnqvist et al. highlight that ca. 6000 km2 of land are expected to be lost over the coming 50 years due to RSLR and the erosion/drowning of coastal wetlands. However, this figure cannot directly be compared to our results, because it does not account for upland areas being converted to wetlands as sea level rises; it only accounts for seaward losses due to erosion and/or drowning with associated shoreline retreat and land loss3. Equivalent scenario runs of our model (i.e. only considering wetland accretion, but no inland migration) result in a comparable projected wetland loss in Louisiana of ca. 6,900 km2 until 2100, under the medium SLR scenario (RCP4.5). This loss is triggered by insufficient sediment availability for the marshes to keep pace with SLR in situ. Hence, Törnqvist et al.’s claim that our model underestimates future wetland loss on the US Gulf coast is incorrect. Rather, we demonstrate that our global-scale model predictions of wetland losses are comparable to regional estimates

Adaptation to multi-meter sea-level rise should start now

Sea-level rise will fundamentally change coastal zones worldwide (Cooley et al 2022). A global two meters rise of sea level will be exceeded sooner or later within a time window ranging from one century to as long as two millennia, depending on future greenhouse gas emissions and polar ice-sheet melting (Fox-Kemper et al 2021). Here, we show that in addition to climate mitigation to slow this rise, adaptation to two meters of sea-level rise should start now. This involves changing our mindset to define a strategic vision for these threatened coastal areas and identify realistic pathways to achieve this vision. This can reduce damages, losses, and lock-ins in the future, identify problems before they become critical and exploit opportunities if they emerge. To meet this challenge, it is essential that coastal adaptation becomes core to coastal development, especially for long-lived critical infrastructure. Coastal adaptation will be an ongoing process for many decades and centuries, requiring the support of climate services, which make the links between science, policy and adaptation practice

Author Correction: A global analysis of subsidence, relative sea-level change and coastal flood exposure (Nature Climate Change, (2021), 11, 4, (338-342), 10.1038/s41558-021-00993-z)

A Correction to this paper has been published: https://doi.org/10.1038/s41558-021-01064-z