The African coast contains heritage sites of ‘Outstanding Universal Value’ that face increasing risk from anthropogenic climate change. Here, we generated a database of 213 natural and 71 cultural African heritage sites to assess exposure to coastal flooding and erosion under moderate (RCP 4.5) and high (RCP 8.5) greenhouse gas emission scenarios. Currently, 56 sites (20%) are at risk from a 1-in-100-year coastal extreme event, including the iconic ruins of Tipasa (Algeria) and the North Sinai Archaeological Sites Zone (Egypt). By 2050, the number of exposed sites is projected to more than triple, reaching almost 200 sites under high emissions. Emissions mitigation from RCP 8.5 to RCP 4.5 reduces the number of very highly exposed sites by 25%. These findings highlight the urgent need for increased climate change adaptation for heritage sites in Africa, including governance and management approaches, site-specific vulnerability assessments, exposure monitoring, and protection strategies.

Sea level rise is expected to cause chronic shoreline retreat, affecting over 10% of the world’s population in low-elevation coastal zones (LECZ). Sandy beaches supported by man-made structures are more vulnerable to substantial beach area loss due to restricted landward migration, affecting ecosystem services. However, the global extent of ‘hardened’ sandy coastlines at risk of ‘severe beach loss’ has not been comprehensively quantified. Here, using products and geospatial datasets derived from satellite imagery, we find that, 33% of the world’s sandy coastline is currently hardened. Analysis of the results by IPCC AR6 regions show that the most hardened coastal regions are the Bay of Bengal, Western & Central Europe, the Mediterranean, Western North America, and East Asia. Linking coastal hardening information with existing shoreline retreat projections, we find that under SSP5-8.5, up to 26% of the world’s sandy coastline (~52,100 km) is likely to face severe beach loss by the end of the 21^st century. Under a moderate emissions scenario (SSP2-4.5), this projection decreases to 21% (~42,080 km), highlighting the potential mitigation gain. The results also show that the vast majority of projected severe sandy beach losses are in high and upper-middle-income countries, with up to 82% of severe losses under SSP5-8.5 and up to 81% under SSP2-4.5 by the end of the 21^st century, relative to the total length of sandy coastline, including both hardened and natural coastlines. The IPCC AR6 regions with the highest projected sandy beach losses include Eastern North America, Northern South America, the Mediterranean, the Bay of Bengal, Western Africa, and South-east Asia.

Coastal communities around the world are becoming increasingly vulnerable to climate change driven natural hazards. Yet, a global scale coastal vulnerability assessment has not been attempted to date. Here, by employing currently available global datasets together with the widely used Coastal Vulnerability Index (CVI) approach, we assess present-day coastal vulnerability at the global scale. Our country level assessment shows that median coastal vulnerability is highest in Aruba, Benin, Togo, the Democratic Republic of the Congo, Bonaire, Sint Eustatius and Saba, Sri Lanka, Nigeria, French Guiana, Ghana and Liberia. At the IPCC AR6 region scale, Central North America, and Northern South America emerge as the regions with the highest median coastal vulnerability. Results at both country and regional scales indicate that tropical and subtropical regions are more vulnerable to coastal hazards. In countries with High or Very High median CVI, the dominant contributors to present-day coastal vulnerability are geomorphology, mean tidal range, and coastal slope.

Estuaries are continuously adapting to anthropogenic pressure. Because of sea-level rise and reduced fluvial sediment supply, they are at risk of sediment starvation. Contrarily, some estuaries require frequent dredging after artificially deepening the channel to maintain port operations. To optimize current estuarine functions and make estuaries more resilient to future threats, improved understanding of estuarine development after system changes is essential. This paper investigates the estuarine response related to two large-scale human interventions: (1) altering channel depth, following global trends of channel deepening for port navigability; and (2) creating or restoring wetlands, a nature-based solution increasingly explored for its ecosystem services. A schematized 2D-morphological model is set up using Delft3D-FM reflecting a highly engineered estuary in a micro-tidal and wave-dominant environment. Results demonstrate how channel deepening (from 13 m to 17 m, without wetland presence) increased sedimentation in the channel by +31%. Sedimentation rates in the wetland were mostly unaffected by channel depth. After restoring the wetland area (wetland width from 0 km to 1 km, constant channel depth of 15 m), sedimentation within the channel was reduced by $-72$%. The wetland area not only served as sediment sink, but also increased the tidal flow, diminishing sedimentation throughout the estuarine channel. Further analysis showed that restoring wetland areas along a specific segment mostly affected channel sedimentation locally (i.e., at the channel segment along the restored wetland). As such, to alleviate dredging operations at critical locations in the navigation channel, strategic restoration of wetlands can be considered which can provide a sustainable alternative to dredging within highly engineered estuaries.

Important heritage sites along the African coast are at risk from the threats associated with rising sea levels. Here, we quantify the exposure of natural and cultural heritage sites in Africa to coastal flooding and erosion in the 21st century. We develop a comprehensive database of 284 coastal African Heritage Sites (AHS), composed of 213 natural and 71 cultural heritage sites, which is then combined with coastal flooding and erosion projections to assess exposure to coastal extreme events for a moderate (RCP4.5) and high (RCP8.5) greenhouse gas emissions scenario. We find that 56 AHS are presently at risk from a 100-year extreme sea-level event, with a total exposed heritage area of 2,222 km². Most of the currently exposed AHS are located in Northern and Western Africa. By mid-century, the number of exposed AHS is projected to increase more than 3 times to reach 191 and 198 under moderate and high emissions respectively. In the second half of the century, the number of exposed sites stabilizes, but the median exposed area increases to 6.6 to 8.5 times the present-day value, under moderate and high emissions, respectively. Mitigation from high to moderate emissions will reduce the end-century median exposed area and number of very highly exposed sites by 20% and 25% respectively.

Estuaries worldwide are under constant anthropogenic pressure. They are susceptible to climate change effects, from the sea (sea level rise, changing wave climate) and from the river-side (changing river discharge). Besides, estuaries are channelised and embanked to improve flood safety and to reclaim land, and channels are deepened to allow bigger ships to enter the ports. To optimise estuarine functions and sustainably prepare for future challenges, improved understanding of estuarine sediment dynamics after potential changes in the systems configuration and forcings is desired. This paper aims to assess the annual sediment dynamics of an estuary under a climate change effects, and how this is affected by human interventions.