The number of “megacities” has more than doubled since 1990
According to UN-Habitat, megacities are high density metropolises with at least 10 million inhabitants. The number of these megacities climbed from 10 in 1992 to 21 in 2010, a 110% increase, adding on average one megacity every two years. Fifteen of the world’s 21 megacities are found
in developing countries. The largest megacity today is Tokyo which counts nearly 37 million persons, more than Canada’s total population.
With large and dense metropolises come the associated environmental impacts of urban life. Very dense population structures and people living in close quarters bring sanitation, waste management, air quality, pollution
and other concerns for residents and the environment alike. Not only do anthropogenic factors play a major role in megacities but the natural environment also presents risks to highly concentrated populations including floods, mudslides, tsunamis and earthquakes (UN 2009b, UN- Habitat 2009).
This graphic is part of the publication Keeping Track of Our Changing Environment