I used to think that a city is made up of buildings, people, utilities, social and political relationships, communication networks, green areas and so on, and that its limits are visible and recognizable. Later on, it became clear that a city has an extended area of influence, derived from complex territorial relationships, administrative borders, long distance transportation routes… But only recently I read a study on Hong Kong from the perspective of food consumption in relation to the city [1]. Seen from the perspective of the surface needed to grow food for its inhabitants, a city’s surface grows beyond visible and administrative territories, expanding widely…

The calculations state that for a city of 1.000.000 people, with a density of 300 persons/hectare, that determine a occupied surface of 3333 hectares, a surface of 1.500.000 hectares is acctually needed to grow food. This is a diagram made to envision the difference between built territory and the surface needed to grow food, for HK…

HK area necessary for food

… and it made me think about growing a roof garden. I also tried to calculate my carbon footprint for the first time, and it seems that all the bicycling I did this summer doesn’t compensate for the heating system I’m currently using.

[1] – Brenda Vale, Rober Vale. Is the High-Density City the Only Option?, Designing High-Density Cities for Social and Environmental Sustainability, by Edward Ng