Currently more than half of the worlds human population lives in urban areas and this is continuing to grow.  Most of this growth will be in developing countries.

Urban centers are increasing in size and number. At the beginning of the last century, there were only 11 megacities in the world with populations of more than 1 million each. By 2030, UN predicts that there will be more than 500 cities in the world with populations of more than 1 million each; more than half of these cities will be in Asia.

In addition, the peri-urban areas in many big cities are rapidly expanding. With an increasing population density, especially in peri-ruban areas, the establishment of the required supply and disposal infrastructure  gets more and more difficult, which leads to rising environmental and health problems.

The mitigating air and water pollution, combined with the effects to climate change in different regions have become more serious concerns.

At the same time, cities have a huge potential to act as hubs for the development of smart, sustainable solutions that can help meet human needs within minimal footprints while still improving quality of life.

The key challenge is the transformation from a linear economy to circular econmy, targeting to establish so called green and sustainable cities.
For sustainable cities, ecosystem services in and outside the city are key assets that provide a wide range of values: environmental, economic, social, and cultural. High quality urban greenery and urban water bodies produce multiple benefits in biodiversity, climate regulation, improved public health, and quality of life – thereby raising both the attractiveness and sustainability of the city. In many growing cities there is a continuous conflict between conservation and development.

So decision-makers must act effectively to preserve, restore and even create urban greenery and urban water bodies. This requires them to implement tough, innovative and proactive planning, with a holistic perspective and cooperation across sectors.