The Global Impacts of Cities

到2050年，全球人口将达到约90亿，我们中75%的人将生活在城市。许多全球环境系统已经承受着严重的压力，对水、生物多样性、气候变化和养分循环等产生了影响。工程师们面临着巨大的挑战，在我们不断发展的城市规划和设计基础设施，在地球的承载能力范围内工作。研究的目标是了解城市的增长如何影响全球环境系统。其目标是超越了解单个城市的环境影响(足迹)，量化全球范围内所有城市的综合影响。该方法涉及一种新的科学方法，包括两个主要步骤：i)测试和改进城市新陈代谢的数学模型；ii)将该模型扩大到所有城市。这项研究有望改善将城市绿化与全球环境挑战联系起来的公共政策的科学和工程投入。我与几个国际组织，包括C40、经合组织、环境署、人居署和世界银行的合作，推动了这一研究方向。预计它将在不断发展的城市科学和全球环境科学之间建立新的、原创的联系。

By 2050, global population will reach approximately 9 billion and 75% of us will be living in cities. Many global environmental systems are already under severe stress, with impacts on water, biodiversity, climate change, and nutrient cycles, amongst others. Engineers face huge challenges in planning and designing infrastructure for our growing cities, working within the carrying capacity of the planet.The objective of the research is to understand how the growth of cities impacts global environmental systems. The goal is to move beyond understanding the environmental impacts (footprints) of individual cities, to quantifying the aggregate impacts of all cities at the global scale.The method involves a novel scientific approach, composed of two main steps:i) testing and improving a mathematical model of the urban metabolism of cities;ii) scaling up the model to all cities.The research is expected to improve the scientific and engineering input into public policies that link the greening of cities with global environmental challenges. The research direction has been motivated through my work with several international organizations, including C40, OECD, UNEP, UN-Habitat, and the World Bank. It is expected to make new, original connections between the evolving science of cities and global environmental science.