Sustainable Intensification of Rice Agriculture in Vulnerable Mega-Deltas: A Global Challenge

世界上主要的河流三角洲——农业生产的热点地区，支撑着农村生计，养活着全球大部分人口——正面临着重大的可持续性危机。这是因为它们正面临着被海平面上升“淹没”的威胁，这可能会给在那里生活和工作的5亿人带来严重后果。特别是，“淹没”的过程意味着三角洲正在迅速失去土地（预计到2100年，仅南亚和东南亚的主要三角洲就会因海平面上升而失去多达20%的土地），同时加剧了洪水和土壤盐碱化问题。这些问题正在形成一场“完美风暴”，使农业面临越来越大的挑战，而与此同时，这些富饶、肥沃的土地正面临越来越大的压力，需要生产更多的粮食来支持快速增长的全球人口。世界第三大三角洲湄公河是东南亚的粮仓，是近2000万人口的家园，但由于气候变化和经济的快速发展，它正面临严重的环境风险，最明显的是湄公河上游集水区水电大坝的开发，切断了三角洲的沉积物供应。因此，湄公河不仅代表了世界三角洲面临的许多问题，而且迫切需要可靠的数据来帮助制定可持续的管理计划，为三角洲居民提供安全的经营空间。在我们之前的工作中，我们已经证明了三角洲内部和流经三角洲的水、沉积物和相关营养物质的流动对水稻种植策略的恢复能力至关重要。沉积在三角洲的沉积物有助于抵消海平面上升，而且由于它们含有丰富的营养物质（氮和磷），它们非常肥沃。该提案关注的关键问题是，湄公河三角洲的许多贫困农民（超过350万农民生活在贫困线以下）依靠河流沉积物提供的免费施肥来降低他们的“投入”成本（用于购买和使用人工肥料以维持水稻生产的收入的一部分）。因此，在自然沉积物沉积的积极影响（三角洲建设和自由施肥）与导致它的洪水过程的负面影响之间存在权衡。随着未来沉积物和养分通量的下降（由于上游水坝截流沉积物），需要采用新的方法来为适应战略（如有管理的洪水）提供信息，以确保脆弱社区未来能够继续可持续地耕作。在这一建议中，我们将与越南伙伴合作，引进英国在以下方面的专门知识：(i)洪水、沉积物运输和养分通量的建模；农业生计；（iii）参与性利益相关者参与过程和（iv）应对这一挑战的社会生态系统动态。通过汇集这些专业知识，并与我们的越南同事和利益相关者密切合作，我们将能够确定未来变化的政策相关情景，量化洪水、沉积物和养分沉积与农业生计之间的联系，并开发新的建模工具，以便在未来环境变化时评估洪水和养分供应之间的权衡。我们将能够验证一种新方法的概念，该方法可以对推动生计变化的因素进行综合评估，并探索适应的影响，从而实现更可持续的水稻农业集约化。这项工作将在一个具有全球意义的标志性三角洲内进行，为全球南方其他脆弱三角洲的类似分析提供模板。

The world's major river deltas - hotspots of agricultural production that support rural livelihoods and feed much of the global population - are facing a major sustainability crisis. This is because they are under threat from being 'drowned' by rising sea levels, with potentially severe consequences for the 500 million people who live and work there. In particular, the process of 'drowning' means that deltas are rapidly losing land (up to 20% of land is projected to be lost to sea-level rise by 2100 in the major deltas of south and southeast Asia alone), while simultaneously exacerbating problems of flooding and soil salinization. These problems are creating a 'perfect storm' that makes agriculture increasingly challenging, at precisely the time when the pressure is increasing for these rich, fertile, landscapes to produce more food to support rapidly growing global populations. The world's third largest delta, the Mekong, is SE Asia's rice basket and home to almost 20 million people, but it is being exposed to severe environmental risks as a result of climate change and rapid economic development, most notably from the development of hydropower dams in the Mekong's catchment upstream which are cutting off the supply of sediment to the delta. The Mekong is therefore not only representative of many of the issues facing the world's deltas, but reliable data are urgently needed to help inform the sustainable management plans required to provide a safe operating space for the delta's inhabitants. In our prior work we have demonstrated that flows of water, sediment and associated nutrients within and through deltas are critical to the resilience of rice cultivation strategies. The sediments that are deposited in the delta help to offset sea level rise and they are very fertile because of the abundant nutrients (nitrogen and phosphorous) they contain. The key issue that is the focus of this proposal is that many of the Mekong delta's poor farmers (over 3.5 million farmers live below the poverty line) rely on the free fertilisation provided by river sediment deposition to reduce their 'input' costs (the portion of their income that is spent on purchasing and applying artificial fertiliser to maintain rice production). There is therefore a trade-off between the positive effects (delta building and free fertilisation) of natural sediment deposition versus the negative effects of the flooding process that causes it. As sediment and nutrient fluxes decline in the future (as a result of sediment trapping by dams upstream), new approaches are needed to inform adaptation strategies (such as managed flooding) to ensure that vulnerable communities can continue to farm sustainably in the future. In this proposal we will collaborate with Vietnamese partners to bring UK expertise in (i) the modelling of floods, sediment transport and nutrient fluxes; (ii) agricultural livelihoods; (iii) participatory stakeholder engagement processes and (iv) social-ecological systems dynamics to bear on this challenge. By bringing together this blend of expertise and working closely with our Vietnamese colleagues and stakeholders we will be able to define policy relevant scenarios of future change, quantify the links between flooding, sediment and nutrient deposition and agricultural livelihoods, and develop new modelling tools that will be able to evaluate the trade-offs between flooding and nutrient supply as the future environment changes. We will be able to concept-proof a new approach that can deliver an integrated assessment of the factors driving changes to livelihoods and explore the effects of adaptations that could enable more sustainable intensification of rice agriculture. This will be done within a globally significant, iconic, delta, providing a template for similar analyses in other vulnerable deltas in the Global South.