Officials of China‘s National Development and Reform Commission (NDRC) have stated that urban planning at multi-city level is now being prepared nationally. More than 20 urban agglomerations around the country will be classified in order to provide strategic level guidance on development goals, infrastructure construction and function orientation. The systematic guidance is intended to clearly differentiate urban development goals for cities within agglomeration areas by providing development direction for networks and infrastructure, promoting city-specific features and regional positioning and primarily acts to emphasize inter-operability and collaborative development.
Upon first reading, the concept of undertaking large scale regional planning at a co-ordinated level seems just plain old good common sense. It is obvious that transport and resource infrastructure needs to be considered on as wide a platform as possible and that specialisation and economies of scale are necessarily considered.
It's on consideration of where this might actually lead that it becomes rather more alarming. After spending some time trying to obtain further details, beyond the short news release, concerning any Terms of Reference for agglomeration planning and what the overarching intention might be we drew a blank. There are real concerns therefore that identifying @agglomeration zones@ is the first step towards the actuality of physically creating these 20 Mega-Mega-cities.
Is that a bad thing? Both yes and no.
Urban and rural population as proportion of total population, by major areas, 1950–2050/ World Urbanization Prospects: The 2014 Revision
Cities offer undeniable opportunities to expand access to the key services of education and healthcare for large numbers of people in an economically efficient manner. They are also typically able to provide public transportation, housing, electricity, water and sanitation for a densely settled population in a cheaper and less environmentally damaging manner than providing a similar level of services to a predominantly rural household. Importantly, urban dwellers also have access to larger and more diversified labour markets, widen their marriage prospects, are able to sample a wider variety of leisure and entertainment and generally enjoy more choices overall.
There are down points. Chief amongst these are the detachment from family and friends, initial sense of alienation, high cost of living, pollution and stress.
Significantly, urban areas are hotspots of high risk to epidemic，natural disaster and social disruption，given their concentrations of population and infrastructure; their key roles for larger economic, political and social processes; and their inherent instabilities and vulnerabilities.
A vast majority of the world’s rural inhabitants live in Asia, but projected growth is fastest in Africa
Asia will continue to host nearly one half of the world’s urban population
On top of this urban migration is a chief factor in the loss of local cultural traditions and safeguarding of the collective memory, where native languages and customs are lost as they fail to be passed on to younger generations.
It would seem that huge agglomerations potentially lead to a number of problems, amongst them the following:
●reduced opportunity for local decision making;
●increased likelihood of standardisation and generic planning;
●loss of distinct local characteristics;
●requirements for costly underground infrastructure systems;
●space pressures on waste disposal;
●increased incidence of environmental pollution;
●reduction in diversity;
●reduction of food resources close to urban centres;
●increased pressure on natural systems including water, green space and ecology;
●reduced access to the countryside and a disassociation from nature; and
●utilisation of premium quality agricultural land for development;
Global urban population growth is propelled by the growth of cities of all sizes
So at what stage does a city become too big? Is it possible to find a balance between the opportunities of the super city and the benefits of segregation and decentralisation? Just how big should a city be?
Theory has it that when you improve a product you create increased demand for it. Similarly improving the efficiency and liveability of a city will create increased inward migration, exacerbating the pressure on problem to be solved.
History has shown that policies that aim to restrict rural-urban migration are ineffective at forestalling city growth, and can even produce economic, social and environmental harms. So in recent years, a growing number of countries have been favouring other strategies for rural and urban development, such as allocating land rights, managing land use, land redistribution, creating regional development zones and promoting economic diversification and competitiveness in rural areas through the mobilization of investment and the improvement of rural livelihoods. 
The ten largest urban agglomerations in 2014 show varied growth patterns both in the recent past and in future projections
As of 2014，close to one half of the world’s urban population lived in settlements of fewer than 500,000 inhabitants. Whilst this proportion is projected to shrink over time, by 2030 these small cities and towns will still be home to around 45 per cent of urban dwellers. The proportion of the urban population in small cities varies considerably across regions. Close to two thirds of Europe’s urban dwellers reside in small urban places as do more than half of Africa’s urban dwellers. In contrast, just one third of urban residents in Northern America live in settlements with fewer than 500,000 people. Regional differences also reflect differences in settlement patterns, as well as variations in the definition of urban areas across countries and regions.
As China continues to urbanize, sustainable development challenges will need to be increasingly concentrated in cities, particularly in the lower-middle-income brackets where the pace of urbanization is fastest. However policies aimed at a balanced distribution of urban growth, avoiding excessive migration to very large urban agglomerations, may best support such sustainable development. Improving the facilities and opportunities of one hundred dispersed， rural towns to increase their size to 500，000 people may well prove a far more satisfactory solution than agglomerating cities into concentrations of 50 million people.
Population distribution by city size varies across major areas in 2014
Balanced distribution and promoting the growth of intermediate-size cities，common in Latin America, can help to address the problems of excessive centralization of economic and administrative functions, while also responding to the challenges of providing educational and life quality opportunities for the urban poor, and mitigating the negative environmental impacts often associated with large and rapidly growing urban agglomerations.
The NDRC announcement gives no specific announcement of the intent to create these huge urban conurbations，merely to strategically plan at these levels to avoid the pitfall highlighted above. However the writing is on the wall and the stakes are very high.