Half of the world's population, some 3.5 billion people, live in cities. And that number is only expected to increase: by 2030, nearly 60 percent of all people worldwide may be living in urban areas. Virtually all of this urbanization, 95 percent, is taking place in developing countries. Unfortunately, that growth of "urban area" includes slums. Today, 823 million people already live in those slums, but that number will continue to grow.
Sustainable growth is the biggest challenge of the cities of the future. Despite the large number of people living in cities, all cities cover only three percent of all land area. Yet cities can make a big difference: they account for about 60 - 80 percent of all energy consumption and about 75 percent of carbon emissions. Rapid urbanization weighs heavily on getting or keeping fresh water supplies, functioning sewers, habitat and public health.
At the same time, high population density in cities also has advantages. For example, it is easier to use resources more efficiently; implement technological innovations widely; and use fewer resources and energy. Through innovation and progress, the city of the future must provide opportunities for all, including access basic services such as clean drinking water, housing, energy, transportation and more.