The response of coastal wetlands to sea-level rise during the twenty-first century remains uncertain. Global-scale projections suggest that between 20 and 90 per cent (for low and high sea-level rise scenarios, respectively) of the present-day coastal wetland area will be lost, which will in turn result in the loss of biodiversity and highly valued ecosystem services. These projections do not necessarily take into account all essential geomorphological and socio-economic system feedbacks. Here we present an integrated global modelling approach that considers both the ability of coastal wetlands to build up vertically by sediment accretion, and the accommodation space, namely, the vertical and lateral space available for fine sediments to accumulate and be colonized by wetland vegetation. We use this approach to assess global-scale changes in coastal wetland area in response to global sea-level rise and anthropogenic coastal occupation during the twenty-first century. On the basis of our simulations, we find that, globally, rather than losses, wetland gains of up to 60 per cent of the current area are possible, if more than 37 per cent (our upper estimate for current accommodation space) of coastal wetlands have sufficient accommodation space, and sediment supply remains at present levels. In contrast to previous studies, we project that until 2100, the loss of global coastal wetland area will range between 0 and 30 per cent, assuming no further accommodation space in addition to current levels. Our simulations suggest that the resilience of global wetlands is primarily driven by the availability of accommodation space, which is strongly influenced by the building of anthropogenic infrastructure in the coastal zone and such infrastructure is expected to change over the twenty-first century. Rather than being an inevitable consequence of global sea-level rise, our findings indicate that large-scale loss of coastal wetlands might be avoidable, if sufficient additional accommodation space can be created through careful nature-based adaptation solutions to coastal management.

Increased concentrations of atmospheric greenhouse gases have led to a global mean surface temperature 1.0°C higher than during the pre-industrial period. We expand on the recent IPCC Special Report on global warming of 1.5°C and review the additional risks associated with higher levels of warming, each having major implications for multiple geographies, climates, and ecosystems. Limiting warming to 1.5°C rather than 2.0°C would be required to maintain substantial proportions of ecosystems and would have clear benefits for human health and economies. These conclusions are relevant for people everywhere, particularly in low- and middle-income countries, where the escalation of climate-related risks may prevent the achievement of the United Nations Sustainable Development Goals.

The range of future climate-induced sea-level rise remains highly uncertain with continued concern that large increases in the twenty-first century cannot be ruled out. The biggest source of uncertainty is the response of the large ice sheets of Greenland and west Antarctica. Based on our analysis, a pragmatic estimate of sea-level rise by 2100, for a temperature rise of 4• C or more over the same time frame, is between 0.5 m and 2 mthe probability of rises at the high end is judged to be very low, but of unquantifiable probability. However, if realized, an indicative analysis shows that the impact potential is severe, with the real risk of the forced displacement of up to 187 million people over the century (up to 2.4% of global population). This is potentially avoidable by widespread upgrade of protection, albeit rather costly with up to 0.02 per cent of global domestic product needed, and much higher in certain nations. The likelihood of protection being successfully implemented varies between regions, and is lowest in small islands, Africa and parts of Asia, and hence these regions are the most likely to see coastal abandonment. To respond to these challenges, a multi-track approach is required, which would also be appropriate if a temperature rise of less than 4• C was * Author for correspondence (R.J.Nicholls@soton.ac.uk). expected. Firstly, we should monitor sea level to detect any significant accelerations in the rate of rise in a timely manner. Secondly, we need to improve our understanding of the climate-induced processes that could contribute to rapid sea-level rise, especially the role of the two major ice sheets, to produce better models that quantify the likely future rise more precisely. Finally, responses need to be carefully considered via a combination of climate mitigation to reduce the rise and adaptation for the residual rise in sea level. In particular, long-term strategic adaptation plans for the full range of possible sea-level rise (and other change) need to be widely developed.

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To Whom It May Concern We have extensively revised the manuscript 'Global coastal wetland change under sealevel rise and related stresses: the DIVA Wetland Change Model' by Spencer and coauthors, for further consideration for publication in Global and Planetary Change. We believe that we have addressed all the comments and queries raised by the reviewers in detail and in full. Our 'response to referees' indicates where on a manuscript the responses have been made. We believe that these responses have resulted in a significantly improved paper and we thank the referees and the editorial team for the opportunity to respond to the criticism of the original submission. We maintain the separation of the general narrative from a more specific set of technical issues raised in the supplementary material; we believe that this decision helps meet the journal's concern to present problems and results in a way that is suitable for a broad readership. However, for ease of review we include the Supplementary Material at the end of the revised manuscript. The manuscript has been prepared to conform to the instructions for contributors. This material has not been previously published elsewhere, nor is it under consideration for publication elsewhere. All the authors have approved this submission. There are no closely related manuscripts that have been submitted or are in press. As far as I am aware, there are no actual or potential conflicts of interest, of a financial, personal or other kind, with other people or organizations that could inappropriately influence, or be perceived to influence, this work. No funding source has had any involvement in the study design, collection, analysis and interpretation of the data, in the writing of the manuscript and in the decision to submit the paper for publication.

In the version of this Article originally published, in the sentence beginning "Here, we quantify global-mean relative sea-level rise... " in the Abstract, the value '2.5 mm yr -1 ' should have been '2.6 mm yr -1 ' . Furthermore, the sentence "In 2015, this floodplain population is approximately 235 million people. " should have made clear that the value of the floodplain population was for the scenario without subsidence and climate-induced sea-level rise (SLR); it has now been amended to "Without subsidence and climate-induced SLR, the global floodplain population in 2015 would have been approximately 235 million people. " Also, the beginning of the subsequent sentence "Assuming no subsidence and no climate-induced SLR... " has been amended to "Still assuming no subsidence and no climate-induced SLR... " The online versions of the Article have been corrected.

Relative sea/land level changes are fundamental to people living in deltas. Net subsidence is complex and attributed to tectonics, compaction, sedimentation and anthropogenic causes. It can have severe impacts and needs to be quantified and where possible (for subsidence due to anthropogenic causes) avoided. For the highly populated Ganges-Brahmaputra-Meghna delta, a large range of net subsidence rates are described in the literature, yet the reasons behind this wide range of values are poorly understood. This paper documents and analyses rates of subsidence (for publications until 2014) and relates these findings to human influences (development). 205 point measurements of net subsidence were found, reported in 24 studies. Reported measurements were often repetitive in multiple journals, with some lacking detail as to precise location, cause and method, questioning reliability of the rate of subsidence. Rates differed by locality, methodology and period of measurement. Ten different measurement methods were recorded, with radio-carbon dating being the most common. Temporal and spatially, rates varied between -1.1mm/yr (i.e. uplift) and 43.8mm/yr. The overall mean reported rate was 5.6mm/yr, and the overall median 2.9 mm/yr, with 7.3mm/yr representing one standard deviation. These rates were reduced if inaccurate or vague records were omitted. The highest rates were recorded in the Sylhet Plateau, Dhaka and Kolkata. Highest rates were recorded in the last 1000 years, where the mean increased to 8.8mm/yr and a standard deviation of 7.5mm/yr. This could be partly due to shorter-term measurement records, or anthropogenic influence as multiple high rates are often found in urban settings. Continued development may cause rates to locally increase (e.g. due to groundwater abstraction and/or drainage). Improved monitoring is required over a wider area, to determine long-term trends, particularly as short-term records are highly variable. Focus in regions where wide spread development is occurring or is expected would be advantageous.