Through innovative and widespread urban planning, Singapore has become a spectacular model of the types of steps other cities can take to maximize resource efficiency and make a significantly smaller impact on the environment as a whole.

Cities present a sustainability conundrum: though they are the most efficient way to provide infrastructure and services for large populations, they are, in absolute terms, incredibly inefficient.

Cities cover just 2% of the Earth's surface yet consume about 75% of the world's resources, and given that more of the world's population now live in cities than in rural areas, it's clear they are key to tackling climate change and reducing resource use.

Urban administrators face huge challenges to make cities more sustainable. From traffic jams and inefficient buildings to social inequality and housing, the problems are complex and hard to tackle — but not insurmountable.

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