Environmental context will affect achieving long-term Sustainable Development Goals: The case of coastal deltas

Global development for at least the next decade is to be guided by the internationally-agreed Sustainable Development Goals (SDGs) of the United Nations, which aim to improve societal well-being while limiting the impact of development on the environment and climate. Research on the SDGs is booming and awareness is increasing of how socio-economic context will affect local implementation and global achievement of the goals. Yet, the implications of context for the SDGs still receive only a small fraction of SDG research attention, and research explicitly on feedbacks affecting the SDGs in specific environmental contexts is rare.

Using 49 coastal river deltas as a case study, we show that the environmental context of places will affect implementation and achievement of the SDGs. We quantitatively compare pathways to the SDGs between deltas and non-delta areas using three plausible future development scenarios until 2100. The scenarios represent three Shared Socio-economic Pathways (SSPs): SSP1--sustainable development with low challenges for climate change mitigation and adaptation; SSP2--a 'middle of the road' scenario with intermediate challenges; and SSP3--a future with high mitigation and adaptation challenges due to rapid population growth, slow technological change, high inequalities, and weak institutions. We use the Integrated Assessment Model IMAGE to project global gridded outputs related to key SDGs in deltas for each scenario.

Our analysis reiterates the importance of deltas for achieving the SDGs. Population densities in deltas globally could rise as much as ten times that of non-delta areas under the worst case scenario (SSP3). This would place immense pressure on implementing and achieving most SDGs in these places. Similarly, urbanisation of deltas is expected to increase more rapidly than non-deltas, creating challenges for sustainable cities (SDG 11). Many deltas are also saturated with cropland, the demand for which is expected to continue under all scenarios, with implications for achieving zero hunger (SDG 2) in these places and globally, as well as for delta biodiversity (SDG 15). Moreover, urban expansion and intensified agriculture may result in major groundwater extraction, which has dramatic effects on delta subsidence and therefore sustainability in the longer term.

We describe how environmental processes and feedbacks pose serious risk to achieving sustainability goals in deltas, in particular due to their potentially profound delta impacts beyond the SDG time horizon of 2030. These environmental processes are often not captured in socio-economic or integrated assessment modelling, nor in much SDG research to date, which potentially limits large-scale SDG research, planning, and assessment. We argue that the importance of environmental context for achieving the SDGs extends beyond deltas into other environments (e.g., mountains, semi-arid regions). We conclude that greater attention to the biophysical and geomorphological setting of places should be paid in research, planning, and governance for the SDGs.