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The incorporation of stakeholder views is integral to ecosystem service research from initiation to completion. Creating a clear link between research outputs and stakeholder needs places emphasis on stakeholder-identified issues and priorities and helps develop intervention recommendations that are relevant to local users of delta ecosystem services and national decision-makers. Stakeholder mapping is used to identify relevant institutions and local partners prior to one-to-one interviews and workshop participation. A range of interlinked issues, challenges and uncertainties across the social, economic and environmental landscape of Bangladesh are defined and used to develop trends under three future narratives: Business As Usual (BAU), More Sustainable (MS) and Less Sustainable (LS). Maintaining the involvement of stakeholders is a challenge, but provides a major benefit for integrated and credible analysis.

To enable a high-resolution representation at regional and local levels over South Asia, a regional climate model (RCM) with a high-resolution grid and good representation of features such as coastlines and mountains is used to generate 17 climate simulations. For Bangladesh, the results show increasing surface air temperature over the region from the present day (defined as 1981–2000) between 1.5 and 2.7 °C by the 2050s to between 2.6 and 4.7 °C by the 2090s. Precipitation is also projected to increase in the majority of simulations by mid-century (with a range of −1.4 to around +13 per cent) and a clearer consistent signal of increase by the 2090s (+8 to +28 per cent). Assessment of changing rainfall extremes indicates a decrease in light rainfall events, but an increase in heavier events.

Poverty and equity may be influenced directly by the macro-economic enabling conditions as well as macro-economic performance. To enhance the usefulness of scenario narratives with implied economic development paths, components of macro-economic performance related to deltas are identified. Patterns of resource and land ownership, infrastructure, financial capital and natural resource management are among the components discussed and qualitatively projected to 2030. Quantification of future economic variables in integrated analysis is presented with the national and regional policy levers which influence the likelihood of individual development paths. The analysis emphasises that the range of economic and other policy instruments available in Bangladesh can ensure that economic development follows a path that significantly reduces the vulnerability of the population to climate—and other environmental—change.

The Ganges-Brahmaputra-Meghna (GBM) river system is considered to be one large trans-boundary river basin, although the three rivers of this system have distinct characteristics and flow through different geographical regions. A semi-distributed model that can account for the spatial variability across the catchment is used to determine the magnitude and variability in flows, sediments, and nutrients of the GBM rivers in response to changes in precipitation, essential inputs for delta analysis. The model captures the main dynamics of the rise to the peaks in monsoon periods from May to November and the recession curves towards the dry season. Comparison of simulated and observed nitrogen loads in the Ganga River suggest that the model is also simulating realistic nutrient fluxes.

The Bay of Bengal provides important ecosystem services to the Bangladesh delta. It is also subject to the consequences of climate change as monsoon atmospheric circulation and fresh water input from the major rivers are the dominating influences. Changes in marine circulation will affect patterns of biological production through alterations in the supply of nutrients to photosynthesising plankton. Productivity in the northern Bay will also be sensitive to changes in riverborne nutrients. In turn, these changes could influence potential fish catch. The Bay also affects the physical environment of Bangladesh: relative sea-level rise is expected to be in the range of 0.5–1.7 m by 2100, and changing climate could affect the development of tropical cyclones over the Bay.

Recent research highlights that delta submergence is an important issue for the Ganges-Brahmaputra-Meghna (GBM) delta. The only factor that could potentially offset losses in delta surface elevation is a sustainable supply of fluvial sediment. River sediments therefore have considerable economic and social value for ecosystem services and those they support. Analysis, using the HydroTrend model, indicates that an increase in the climate-driven supply of fluvial sediment to the GBM delta has the potential, through accelerated aggradation on the delta surface, to offset some of the adverse impacts of climate change due to rising sea levels in the Bay of Bengal. However, anthropogenic disconnections, such as dams, flood defences and polders disturbances, have the possibility to negatively affect this process.

The magnitude and extent of fluvial, tidal and storm surge flooding in coastal Bangladesh are quantified using hydrodynamic numerical models under a series of climate and sea-level rise scenarios to 2100. Fluvial floods occur from July to October and are confined to the northern part of the coastal region. Tidal floods occur in the southern part of the coastal region along the banks of the estuaries and only last a few hours. The flood extents for both types of flood are influenced by sea-level rise and increased upstream river flows. Flooding associated with cyclone landfall and resulting storm surge also increases in extent, with a nearly four times increase by the end of the century in extreme cases, reinforcing the need for a long-term adaptation strategy.

Understanding how changing climate may affect future salinity levels is important for ecosystem services within the delta. Observations of tidal river salinity in Bangladesh are limited so a field survey of salinity levels and river soundings were undertaken providing calibration for a hydrodynamic model. Modelled changes in salinity levels have a pronounced spatial pattern. The saltiest river waters continue to be found in the western section of the delta, including the Sundarbans. The largest changes are projected in the central estuaries, where rising sea levels move the saltwater front further inland, increasing salinity levels. In the eastern section, increased river flow and rising sea levels are more balanced, and little change is anticipated in future salinity at the mouth of the Meghna River.

Determining soil salinity within the delta is crucial as it is the dominant factor determining crop productivity. There are numerous interacting drivers that influence soil salinity, including climate variability, saline river water inundation, storm surge inundation, depth to groundwater table, groundwater salinity, and shrimp farming (). For the study area, tidal river salinity appears to influence the soil salinity most, particularly in the south-west of the delta. In northern areas, high groundwater salinity levels, combined with a high groundwater table, are a major contributor to soil salinity. In addition, an increase in salinity of dry season irrigation water is expected to increase salt accumulation in soils, with a possibility of irrigation water salinity exceeding five parts per thousand.

Demographic trends and projections have important implications for the use of ecosystem services and sustainability in the delta. The study area accounts for ten per cent of the national population and recently appears to have low rates of population growth. Analysis of components of population change (fertility, mortality and migration) indicates that over the next few decades the population structure will undergo considerable change. These demographic trends are explained by declining fertility, greater life expectancy and high rates of out-migration. More specifically, the proportion of 65 and over is likely to increase from 6 per cent in 2011 to 15–16 per cent by 2051. Conversely, the proportion of children and youth (ages 0–14) would decline from 34 per cent to 15–16 per cent depending on the scenario considered.