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

外行人摘要(最多4000个字符)世界主要的河流三角洲是农业生产的热点，支持农村生计并养活全球大部分人口，但作为“气候变化热点”的三角洲正面临重大的可持续危机。具体地说，人们担心，未来几十年，随着海洋变暖，许多三角洲可能会被海平面上升淹没(仅在南亚和东南亚的主要三角洲，预计就会失去多达20%的陆地)。三角洲“溺水”的过程是一种缓慢发生的危险，相对海平面上升会逐渐加剧河流和沿海的洪水风险，同时加强盐碱入侵。然而，逐渐的环境变化被干旱或极端降雨等极端天气事件的发生所打断，气候模型预测这些事件将更频繁地发生。缓慢发生的灾害与极端事件同时发生，创造了一场使农业变得更加具有挑战性的“完美风暴”，但我们几乎没有洞察到缓慢发生的变化如何与极端事件相互作用。一个关键问题是(很像拳击手在击倒对手之前反复用身体击打来软化对手)，在由于持续变化而面临韧性逐渐下降的系统中，偶尔但具有破坏性的极端气候造成的额外负担可能会导致跨越一个“临界点”，使农业生产在严重的干旱或洪水之后难以恢复。这是一个关键的问题，因为如果我们不能正确地确定重大变化的原因，我们就有可能也会错误地应用“解决方案”。在这个项目中，我们将开发一个新的模型来研究农业生产和生计如何受到不断变化的环境变化和极端天气事件的组合的影响。我们将特别关注旱灾和洪涝灾害。洪水是最危险和代价最高的自然灾害，自1980年以来造成了50多万人死亡和超过1万亿美元的经济损失。它们的地势低洼，加上它们位于海岸和河流环境之间的交界处，这意味着三角洲特别容易受到这些风险的影响。然而，在发展中世界，农业生产是国民经济的支柱，对生计至关重要，干旱可能是水和粮食安全的关键驱动因素，但我们对干旱如何发展、持续和恢复知之甚少。我们将通过探索干旱和洪水事件以及与上游集水区管理和气候变化相关的持续环境压力之间的相互作用，来加深我们对三角洲系统对极端事件的脆弱性的理解。我们的项目重点是世界第三大三角洲--湄公河。湄公河三角洲是东南亚的大米篮子，拥有近2000万人口，但由于气候变化和经济快速发展，该地区面临着严重的环境风险。我们将与我们的越南合作伙伴合作，包括主要的政府机构，将英国在以下方面的专业知识带给英国：(I)干旱和洪水的建模；(Ii)农业生计；(Iii)参与性利益相关者参与进程；(Iv)应对这一挑战的社会生态系统动态。我们将定义未来变化的政策相关情景，并量化干旱和洪水与农业生计之间的联系，对推动生计变化的因素进行综合评估，并探索适应可能产生的影响，以帮助湄公河三角洲更好地适应极端气候。这将在具有全球意义的标志性三角洲内完成，为全球南部其他脆弱的三角洲提供类似分析的模板。

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.