Red Soil CZ: From natural to anthropogenic evolution of Red Soil and its impact on ecosystem function in the Critical Zone Red soils cover 20% of each of China and India, the most populated countries on earth, as well as large areas of developing countries in southeast Asia, Africa and South America. They form in sub-tropical climates where excessive leaching from rainwater has produced an infertile, unstable soil that is very vulnerable to mismanagement, climate change and pollution such as acid rain. In China, red soils support about 40% of the population, made possible through the intensive use of fertilisers to boost crop yields. This farming system is unsustainable; fertilisers reaching groundwater, freshwater and the atmosphere pose a significant environmental threat, and soil degradation through intensive cultivation can result in tens of tonnes of soil being eroded each year from a hectare of land into water courses during the intensive monsoonal, spring rains. Red soil management for agriculture affects local farmers who depend on them for their livelihood, the surrounding population who need them for food, China because of dependence for national food production and globally because of the area red soils covers, their importance for food production and the large environmental footprint.  Although extensive research has studied red soils, particularly related to management for agricultural sustainability, the integrated effects of various affected aspects of the critical zone, as well as the wider environmental impacts are poorly understood. In this proposal we adopt a critical zone approach, to reach beyond soil processes to encompass the atmosphere above, geology and groundwater below, surrounding freshwater and vegetation. By definition, the critical zone is the constantly evolving boundary layer at the surface of the earth where rock, soil, water, air and living organisms interact. Two essential components are essential for delivery. First, we have the major advantage of the Sunjia Critical Zone Observatory (CZO), the only international CZO in China where soil and water data have been collected since 2002. Second, we have assembled a team of Chinese and UK scientists who integrate a range of specialisations in soil science, with atmospheric, geological, hydrological and agronomical sciences. A skill gap identified amongst the Chinese partners in terrestrial environmental modelling is filled by the UK team, with training and joint positions proposed that will develop this capability in China.  We build on existing Sunjia CZO monitoring by incorporating subsurface and atmospheric processes not included in the past. Further experiments in the lab and the field will allow us to explore impacts of environmental threats such as climate change, water scarcity and acid rain. We span from processes involved in weathering minerals, how these minerals interact with life to form soils, and how we can optimise these processes in soil evolution for the benefit of the environment and food security. These processes then enhance our understanding of hydrological and erosion impacts in red soils induced by different management practices. Detailed monitoring of these processes in the Sunjia CZO and other red soil areas provides data that inform our modelling of ecosystem processes. This process benefits immensely from a critical zone monitoring data-set for red soils that will span almost 20 years by the end of the project.  The new science generated in this project, particularly the modelling outputs, provides valuable data for policy decisions in China about the management of red soils. We provide training to project partners in interdisciplinary science that is essential to CZO research and will benefit the research capabilities of the Chinese team. Moreover, we bring new skills to the Chinese team in terrestrial modelling. Coupled with our intended outcome of more sustainable food production from red soils, our training and government agency engagement ensures delivery of OECD Official Development Assistance from this project. The Newton Fund builds research and innovation partnerships with developing countries across the world to promote the economic development and social welfare of the partner countries.