The growing importance of shrinking wetlands: a tale of three cities

摘要

Globally, around three million people move to urban areas every week; 54% of the world's population live in urban areas, and cities account for 85% of global GDP generation.1 With only 1% of the world's total land mass, cities are home to over 50% of the human population (Wang et al. 2018). A rapidly growing urban population comes with enormous challenges for city planners and managers. They have to ensure that cities today can deliver not only basic services such as accommodation, transport and water but that they are safe, resilient and environmentally friendly. Cities are also aggregators of materials and nutrients, accounting for 75% of natural resource consumption, 50% of global waste production, and 60-80% of greenhouse gas emissions (Ellen MacArthur Foundation 2017). Cities, particularly in economically developing countries face multiple major challenges, including a rapid increase in urban populations with limited access to social services, burgeoning municipal waste generation, inefficient infrastructures and air pollution.