It is estimated that three million people around the world are moving to cities every week, with migration driving much of the increase in urbanisation, according to new research.

The movement of people is making cities much more diverse places in which to live. Nearly one in five of the world foreign born population resides in established global gateway cities.

London, England
In many of these cities, such as Sydney, London and New York, migrants represent over a third of the population and, in some cities such as Brussels and Dubai, migrants account for more than half of the population.

Other cities have seen a remarkable growth in migration in recent years. For example, the number of foreign residents in Seoul has doubled in the last decade. In Asia and Africa, rapidly growing small cities are expected to absorb almost all the future urban population growth of the world.

However, the World Migration Report 2015 from the International Organisation for Migration (IOM) points out that the fast rate of urbanisation and rising migration to cities brings with it both risks and opportunities for the migrants, communities and governments concerned.

It looks at how migration and migrants are shaping cities, and how the life of migrants, in turn, is shaped by cities, their people, organisations and rules. This has an impact on housing and health. But migrants can help to build and revive cities with their resources and ideas.

The report also identifies innovative examples of how some cities are seeking to manage the challenges of increased global mobility and social diversity with varying degrees of success.

"Migration and how it is governed, should be an issue at the frontline of urban planning and sustainable development. However, migration is largely omitted from the global debate on urbanization. There is a glaring absence of the mention of migrants in international planning for a new global urban agenda," the report says. "Many city and local governments also still do not include migration or migrants in their urban development planning and implementation. Migrants are therefore still generally overlooked in global discourses on urbanisation and cities."

According to the report, over 54% of people across the globe were living in urban areas in 2014 and the current urban population of 3.9 billion is expected to grow to some 6.4 billion by 2050. Migration is likely to be the key driver and overall cities will continue to be much more diverse places in which to live, the report concludes.