The first image that comes to mind when considering environmental sustainability is usually not a densely packed urban landscape. However, since Compact City: A Plan for Liveable Urban Environment was released in 1974 by authors George Dantzig and Thomas Saaty, most urban planners agree that the most effective way to keep the planet green is to pack as many people as possible into compact cities. The most important reason to contain people in cities, they say, is to decrease sprawl, the expansion of urban areas into surrounding land. Not only does the infringement of human populations into undeveloped areas destroy arable soil and ecosystems but it also creates suburbs that are energy inefficient and automobile dependent. Building cities upward rather than outward is the best way to avoid this.↵
If everyone lived in cities, the need for automobiles would be greatly reduced, which would minimisethe pollution they cause and conserve the fossil fuels they require to operate. Studies show that people who live in densely populated cities, like New York, are 40 per cent less likely to own cars and use far less gasoline because public transit is readily available and walking or cycling is often an option. The fact that driving in cities has become increasingly difficult also contributes to people giving it up. With parking restrictions and expensive toll fees to contend with, not to mention the glut of other vehicles that, sadly, remain on the road, many city dwellers simply choose not to drive when there are far more attractive transportation alternatives available.↵
But the environmental sustainability of cities has to do with more than just transportation: it's also about housing. The vast majority of people in high-density cities live in apartment buildings, which are the most energy-efficient residential structures in the world. The shared walls of apartment buildings mean that less heat is lost and thus, less fuel is used to generate it. In addition, because apartments are usually smaller than, say, a typical single-family home in the suburbs, far less electricity is consumed per household - as much as 50 per cent less than in sparsely populated areas, actually. It's thus no surprise that the carbon footprint of most high-density city inhabitants is around 30 per cent smaller than the global average.↵
Ultimately, while being shoulder-to-shoulder with millions of other people may seem unpleasant, it is the best way to handle our ever-growing population while preserving the resources that subsequent generations will need to survive. The cities that exist today are far from perfect, but that just means that there is still a lot that can be done - from replacing diesel fleets with hybrid and electric ones to updating archaic, inefficient infrastructure - to make urban communities not only more sustainable but also nicer places to live.