To reduce current and future coastal flood risk, it is critical to better understand how adaptation measures, including nature-based solutions, can reduce that risk. Globally, hybrid coastal defenses, including a combination of coastal vegetation, such as salt marshes and mangroves, with a dike or sea wall, have been highlighted as a promising adaptation measure. Here, we present a global-scale assessment of the potential risk reduction from mangrove restoration in combination with foreshore dike systems under scenarios of climate and socioeconomic change. We provide a quantitative assessment of the benefits in terms of reduced economic damage, exposed population, and poverty exposure. We evaluate mangrove restoration fronting dikes by accounting for wave–vegetation interaction. If mangrove foreshore dike systems were established along coastlines susceptible to flooding, restoration could potentially reduce expected annual damage by US$800 million and reduce expected affected population by 140,000 annually. These values increase under future projections. Our benefit–cost analysis finds mangrove restoration economically viable for about half of the subnational regions assessed (85 to 105 out of 208). At the global scale, the benefit–cost ratio under future conditions ranges from 3 to 6, with a net present value between US$44 billion and US$125 billion. Because absolute risk values and benefit–cost analysis do not differentiate between relative wealth impacts, we also estimated restoration impacts across different wealth levels. We show that restoring mangroves disproportionately benefits people with lower incomes, as they are often more exposed to coastal flooding and located in areas suitable for mangrove restoration. As such, mangrove restoration in low- and middle-income countries could contribute to the resilience of people in poverty.

The capacity of mangroves to reduce coastal flood risk resulted in legislation for mandatory widths of mangrove greenbelts in several countries with mangrove presence. Prescribed forest widths vary between 50 and 200 m. Here, we performed 216,000 numerical model runs informed by realistic conditions to quantify confidence in wave reduction capacity of mangroves for wind and swell waves. This analysis highlights that tidal flat areas fronting mangrove forests already account for 70% of reduction in wave heights. Within mangrove forests that are below 500 m wide, wave dissipation is strongly dependent on local water levels, wave characteristics and forest density. For forest widths of over 500 m, which constitute 46% of global coastal mangroves, around 75% or more of the incoming wave energy is dissipated. Hence, for relying on mangroves to dampen shorter waves, a new standard should be adopted that strives for mangrove widths of 500 m or more.

Recent remote sensing analysis has revealed extensive loss of tidal flats, yet the mechanisms driving these large-scale changes remain unclear. Here we show the spatiotemporal variations of 2,538 tidal flat transects across China to elucidate how their morphological features vary with external factors, including suspended sediment concentration (SSC), tidal range, and wave height. We observe a correlation between flat width and SSC distribution, and between flat slope and tidal range. A nation-wide decline in flat width is observed together with SSC reduction between 2002 and 2016. Intriguingly, sediment-rich flats exhibit more rapid width losses if SSC reduces, but slower width gain if SSC increase compared to sediment-starved flats. These dynamics resemble stretched (sediment-rich) or compressed (sediment-starved) springs that tend to return to equilibrium, which can be explained by synthetic morphodynamic modeling. Similar patterns can be observed from Indonesia, the United States, and Australia, implying that the impact of sediment supply change is wide-spread and large-scale sediment allocation plan based on equilibrium concept can help preserving intertidal ecosystems.

Correction to: Communications Earth & Environmenthttps://doi.org/10.1038/s43247-025-02178-4, published online 3 April 2025 In the version of the article initially published, the title and legend for Fig. 5 was duplicated from Fig. 4; the colour descriptions in the legends to Figs. 3 and 4 were incorrect; the zenodo link in the Data Availability section (https://doi.org/10.5281/zenodo.14872179 (2025)) was missing; and the legend to Supplementary Fig. 1 was missing data source citations. The changes are made in the HTML and PDF versions of the article.

Due to rising sea levels and projected socio-economic change, global coastal flood risk is expected to increase in the future. To reduce this increase in risk, one option is to reduce the probability or magnitude of the hazard through the implementation of structural, Nature-based or hybrid adaptation measures. Nature-based Solutions in coastal areas have the potential to reduce impacts of climate change and can provide a more sustainable and cost-effective alternative to structural measures. In this paper, we present the first global scale assessment of the benefits of conserving foreshore vegetation as a means of adaptation to future projections of change in coastal flood risk. In doing so, we extend the current knowledge on the economic feasibility of implementing global scale Nature-based Solutions. We show that globally foreshore vegetation can contribute to a large decrease in both absolute and relative flood risk (13% of present-day and 8.5% of future conditions in 2080 of global flood risk). Although this study gives a first proxy of the flood risk reduction benefits of conserving foreshore vegetation at the global scale, it shows promising results for including Nature-based and hybrid adaptation measures in coastal adaptation schemes.