Urban green infrastructure: optimising local food and fuel production for regional sustainability and resilience

现在，世界上一半以上的人口生活在城市地区。因此，城市地区是全球变化的关键驱动力，占全球碳排放的70%。英国政府承诺到2050年将二氧化碳排放量在1990年的基础上减少80%。最大限度地提高当地能源和粮食产量可以为实现这一目标提供一个关键机制。城市绿色基础设施(UGI)(如公园、花园、荒地、配给)是英国城市的重要组成部分，通常为50%。然而，还没有对UGI支持当地可持续粮食和生物燃料生产的潜力进行定量评估。研究表明，UGI有潜力为城市居民提供许多关键的生态系统服务，如洪水缓解、污染物渗透、碳储存。土壤是陆地生态系统的基础，土壤有机碳(OC)对其支持生态系统服务的能力至关重要。然而，直到最近，人们还认为城市土壤质量较差，不能对生态系统服务的提供作出重大贡献。我的研究在揭示全国重要的城市土壤有机碳储量方面起到了变革性的作用。在英格兰东北部的UGI，我发现35%的土壤有机碳是黑碳(BC)--化石燃料和生物质不完全燃烧的产物，包括从烧焦的生物质到烟尘的一系列分子。测得的高土壤BC浓度可归因于化石燃料排放，而且往往与重金属(HM)污染物呈正相关。利用UGI进行自我种植可以提供一种提高粮食安全的工具，但由于HM在城市土壤中的积累，与自我种植相关的健康存在潜在风险。在自己种植的食物链中，控制HM运动的土壤成分尚不确定，但最近的研究表明，BC可能会减少植物的吸收。我的研究显示，UGI内的土壤通常比农业土壤质量更高，这揭示了可持续食品和燃料生产的潜力。在莱斯特，我发现配额对当地的粮食安全做出了重大贡献，只覆盖了大约1.5%的城市。4500人正在进行“一天五份”的节食。至关重要的是，自给自足已被政策制定者视为当地粮食安全的关键贡献者。相比之下，使用短轮作林木(SRC)生产生物燃料的指导方针只关注农地，但这些指导方针并不排除城市地区。事实上，城市边缘地区已被确定为适合SRC。我们证明了8%的莱斯特是适合SRC的。这可以为1560户家庭提供能源，同时产生生物炭，从而提高土壤质量，并潜在地减少污染物对植物的可获得性。尽管有这些证据，但还没有关于UGI如何为当地粮食和生物燃料生产做出贡献的系统的英国规模评估。这项研究将提供对当前国家自种粮食产量的第一次估计。这一研究计划中使用的新方法将结合高分辨率地理信息系统数据集、英国尺度下BC和HM的地理空间参考土壤化学分析、模拟历史和当前排放数据，以及土壤-植物生长实验，以了解推动粮食和生物燃料作物从土壤中吸收HM的机制。当这些技术结合在一起时，将提供一个强有力的工具来确定UGI在全国范围内提供粮食和生物燃料的能力。潜在的自种作物产量估计将在一系列吸收情景下建立模型。将对UGI潜在的英国生物燃料和生物炭产量进行建模，并估计对可再生能源目标的贡献。将评估将UGI用于粮食和生物燃料生产以及对生态系统服务的影响之间的权衡，并量化缓解农业用地压力的潜力。

More than half of the worlds' population now live in urban areas. Consequently, urban areas are key drivers of global change and are responsible for >70% of carbon emissions. The UK government has committed to reduce CO2 emissions by 80% on 1990 values by 2050. Maximising local energy and food production could provide a key mechanism to achieve this goal. Urban green infrastructure (UGI) (e.g. parks, gardens, wasteland, allotments) represents a substantial component, typically >50%, of UK cities. However, there has been no quantitative evaluation of the potential for UGI to support sustainable local food and biofuel production.Research has demonstrated the potential of UGI to provide many key ecosystems services to urban inhabitants, e.g. flood mitigation, pollutant infiltration, carbon storage. Soils are the foundation of terrestrial ecosystems, and soil organic carbon (OC) is crucial to their ability to support ecosystem services. However, until recently urban soils were assumed to be of poor quality and unable to contribute significantly to ecosystem service provision. My research has been transformative in revealing nationally important OC stocks in urban soils.In the UGI of North East England I found that 35% of soil OC was black carbon (BC) - the product of the incomplete combustion of fossil fuels and biomass, which includes a range of molecules from charred biomass to soots. The high soil BC concentrations measured are attributable to fossil fuel emissions and are often positively associated with heavy metal (HM) pollutants. Using UGI for own-growing could provide a tool to increase food security, but, there are potential risks to health associated with own-growing due to the accumulation of HM in urban soils. The components of soils that control HM movement in the own-grown food chain are undetermined, but recent research suggests that BC may reduce uptake by plants.My research revealed that soils within UGI are typically of higher quality than agricultural soils, revealing potential for sustainable food and fuel production. In Leicester, I found that allotments make a significant contribution to local food security, covering only 1.5% of the city they feed approx. 4,500 people on their '5 a day' diet. Crucially, own-growing has been recognised by policy makers as key contributor to local food security. In contrast, the guidelines for biofuel production using short rotation coppice (SRC) focus exclusively on agricultural land, but, these guidelines do not preclude urban areas. Indeed the urban fringe has been identified as being suited to SRC. We demonstrated that 8% of Leicester was suitable for SRC. This could supply energy to >1560 homes, whilst simultaneously producing biochar which can enhance soil quality and potentially reduce pollutant availability to plants. Despite this evidence there have been no systematic UK scale assessments of how UGI could contribute to local food and biofuel production.This fellowship will provide the first estimate of current national own-grown food production. The novel approach used in this research program, will combine high-resolution geographic information systems datasets, and geospatially referenced soil chemical analysis for BC and HM at a UK scale, modelled historic and current emissions data, together with soil-to-plant growth experiments to understand the mechanisms driving HM uptake from soil by food and biofuel crops. When combined these techniques will provide a powerful tool to determine the ability of UGI to provide food and biofuel at a national scale. Potential own-grown crop production estimates will be modelled under a range of uptake scenarios. Potential UK biofuel and biochar production in UGI will be modelled and the contribution to renewable energy targets estimated. Trade-offs between use of UGI for food and biofuel production and effects on ecosystem services will be assessed, and potential to relieve pressure on agricultural land quantified.