VIET NAM: Slow Onset Hazard Interactions with Enhanced Drought and Flood Extremes in an At-Risk Mega-Delta

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Layperson Summary (4000 characters max.)The world's major river deltas are hotspots of agricultural production that support rural livelihoods and feed much of the global population, but as 'climate change hot spots' deltas are facing a major sustainability crisis. Specifically, there are concerns that many deltas may in the coming decades be 'drowned' by rising sea levels as the oceans warm (up to 20% of land is projected to be lost in the major deltas of south and southeast Asia alone). The process of delta 'drowning' is a slow onset hazard where relative sea-level rise progressively exacerbates fluvial and coastal flood risk while simultaneously enhancing saline intrusion. However, progressive environmental change is punctuated by the occurrence of extreme weather events such as droughts or extreme rainfall and climate models project that these will occur more frequently. The co-occurrence of slow onset hazards with extreme events creates a 'perfect storm' that makes agriculture ever more challenging, but we have almost no insight into how slow onset changes interact with extreme events. A key question is the extent (much like a boxer 'softening up' her opponent with repeated body blows before landing the knockout punch) to which, in systems facing progressive reductions in resilience as a result of ongoing change, the additional burdens caused by occasional but damaging climatic extremes may cause a 'tipping point' to be crossed which makes it difficult for agricultural production to recover after severe episodes of drought or flooding. This is a critical issue because if we cannot correctly attribute the cause of major change we run the risk that 'solutions' will also be applied incorrectly. In this project we will develop a new model to examine how agricultural production and livelihoods are affected by combinations of progressive environmental change punctuated by extreme weather events. In particular we will focus on episodes of drought and flooding. Flooding is the most dangerous and costly of natural hazards, accounting for over 500,000 fatalities and economic losses of more than $1 trillion since 1980. Their low lying nature, alongside their location at the interface between coastal and fluvial environments means that deltas are disproportionately exposed to these risks. However, in the developing world, where agricultural production forms the mainstay of national economies and is central to livelihoods, drought can be a key driver of water and food (in)security, but we know significantly less about how droughts develop, persist and recover. We will further our understanding of the vulnerability of delta systems to extreme events by exploring how crop production and livelihoods are affected by the interplay between episodes of drought and flooding and ongoing environmental stress linked to upstream catchment management and climate change. Our project is focused on the world's third largest delta, the Mekong. The Mekong delta is SE Asia's rice basket and home to almost 20 million people, but it is exposed to severe environmental risks as a result of climate change and rapid economic development. We will collaborate with our Vietnamese partners, including in key government agencies, to bring UK expertise in (i) the modelling of droughts and floods; (ii) agricultural livelihoods; (iii) participatory stakeholder engagement processes and (iv) social-ecological systems dynamics to bear on this challenge. We will define policy relevant scenarios of future change and quantify the links between drought and flooding and agricultural livelihoods, delivering an integrated assessment of the factors driving changes to livelihoods and explore the effects that adaptations could make to help make the Mekong delta more resilient to climatic extremes. This will be done within a globally significant, iconic, delta, providing a template for similar analyses in other vulnerable deltas of the Global South.