As everyone who has read Judge Dread comics will know, towards the end of this century we will all be living in mega cities each containing hundreds of millions of people. In between these urban oases will lie nuclear wastelands controlled by diabolic super villains.
Actually, in real life, the growing urbanisation of the world is a predicted fact (if there is such a thing).  Today about half of the world’s population lives in cities (3.4 billion).  By 2030, this proportion will grow so that 3 in 5 people alive will be living in a city. Of the 9 billion people on the world at that date (projected – but see some issues on these guess-timates here and here) some 2 billion people “could be living in slum-like conditions in cities worldwide”.  In 2050, the amount of people living in cities is projected to be 6.3 billion.  They will be living in more megacities (more than 10 million people) concentrated in Asia and more medium-sized cities everywhere, but especially in Africa. 
Luckily for us, the University College London and the Lancet have commissioned a report on the “many issues other than health services that contribute to population health in a city environment”. In the report, lead author Professor Yvonne Rydin, of UCL Bartlettt School of Planning, and her co-authors from UCL and worldwide, recommend focussing on the delivery of a variety of urban projects that can have a positive impact on city-dwellers.  Large-scale initiatives can have a massive impact – the report notes the effect that London’s first modern, large-scale, urban sewage treatment facility increased Londoners average life expectancy by 15 years between the 1880s and the 1920s.  With more of us living in cities, projects of this type will be increasingly necessary if we wish to increase people’s life expectancy and quality of life.  (Of course, if people live longer they are a greater burden on the planet...dilemmas. Maybe we should just leave people to die in abject poverty at 40 years of age. That way our lifestyle in the West will not need to change. Yes, that works for me...)
While the report recommends planning by central or community or city authorities of urban development projects, the authors argue for a new way of planning.  This new way must recognise that conditions of complexity make it difficult to plan for every contingency or to plan with every necessary piece of information to hand.  The report cautions that “unintended consequences of policy action are likely to persist”.  Professor Rydin says:

“There should be an emphasis on experimenting with and learning from diverse urban health projects. This can mean supporting communities in their own urban health projects, as with community latrines in Mumbai slums or urban food projects in London and Detroit.” Aside from pointing out problems with proposed urban planning, the report also makes 5 recommendations:

1. City governments should build political alliances for urban health.
2. Governments need to identify the health inequalities in cities.
3. Urban planners should include health concerns in their plans, regulations, and decisions.
4. Policy makers need to recognise that cities are complex systems and urban health outcomes have multiple causes.
5. Experimentation and learning through projects involving local communities is often the best way forward.

Easier said than done I suppose, but I do support the call for community involvement.
There are five case studies that the report draws on, but I would like to highlight a couple only.  The first is a sanitation and wastewater management programme in the slums of Mumbai, India.  The Slum Sanitation Programme sought to provide adequate sanitation (of 1 toilet per 50 people) to one million people who were living in slums on municipal land by 2025.  The scheme builds on the idea that a sense of ownership encourages the community to maintain the toilet blocks, so a fee for the use of the toilets is charged to cover maintenance, water and electricity.  While fees have allowed high standards to be maintained, there are fears that only the relatively wealthier families are able to pay the fee. 
The second case study is the mass transit system in Bogota, Colombia which was introduced in 2000 with dedicated bus lanes and fixed bus stations (before this, people would ask the bus to stop wherever they wanted).  In 2010 this system covered 25% of daily public transport trips and reduced car use and average commuting times.  By reducing congestion, the system has reduced air pollution and has also encouraged users to walk longer distances to bus stations (as they can’t ask the bus to stop outside the door).  This has health benefits, but it doesn’t help the old lady with her groceries I wouldn’t have thought!
So, an interesting report and another example of how people’s ingenuity and intelligence is being used to help us figure out how to live in a more urbanised, more populous world.  It is amazing what we can do if given the chance.  Reports like this are inherently positive and hopeful (as they are predicated on the idea that we can solve our future issues) and do not rely on reducing future populations as the panacea to all our problems.