Megacity is often used to refer to a single city-dominated area. The term was coined long before the globalisation era and therefore does not especially refer to the global dynamics embedded in the use of 'global city-regions'.

Researchers have been talking about global city-regions (GCR) since the late 1990s. A global city-region may have one or more centres of activity. London is a monocentric GCR, having a distinct single city centre. Randstad is a polycentric GCR – it encompasses four primary city centres (Amsterdam, Rotterdam, The Hague and Utrecht) in the Netherlands.

If we only look at how large a monocentric global city-region or a megacity is, the terms megacity and global city-region may be interchangeable. What we really need to consider are their functions, as these elicit the differences between the two.

There is a heightened urgency in understanding this new urban giant, especially in regions where rapid urban changes are taking place. Researchers at the University of Melbourne and Chinese partner institutions have established the Australia/China Research Network on Planning Global City‐Regions. We are using the network as as a platform to exchange knowledge and ideas about global city-region research.

By focusing on mutually interested themes, our network of researchers will be a source of innovation and a bank of world-wide case studies which can be readily accessed by the international research community.

long reach of global city-regions

Global city-regions have ripple effects, creating impact far from their geographic location. A layering metaphor is helpful here – there are interlocking functional layers in any given GCR influenced by economic activity. Some of the functional layers represent a ripple effect which is far reaching.

We see clusters of high end, or producer, services – such as finance, insurance, legal services, design and consultancy – in London and New York, which are top-ranked global cities and the main centres in their respective global city-regions. London and New York connect to (functionally) similar clusters in Singapore, Sydney and many other regional centres all over the world. Decisions made in London and New York flow across the world.

Similar ripple effects also happen on a local level. Tourist attractions in a city-region may initially concentrate events, sport, entertainment and cultural heritage in a central city area, but increases in demand will have impact in surrounding locations. We know that sports events in Melbourne generate more business for tour agencies offering one-day tour trips to the Great Ocean Road, Philip Island, and wineries in country Victoria.

These two examples – high end services and tourism – are not isolated from each other. High end service activities bring in visitors to city-regions, while tourist attractions can trigger improvements to services and facilities, which then trigger growth in high end services.

City-regions in the Australian context

Global city-regions are emerging in Australia. The great Sydney and Melbourne regions, and the Brisbane–Gold Coast region are examples. In Melbourne, the city-region extends to places such as Bendigo, Ballarat and Geelong, and includes tourist attractions such as the Philip Island and the Great Ocean Road area.

Tourist activities provide obvious signals for making the connections between remote locations and the Melbourne city-region; other activities, such as creative industries (arts studios, galleries) are also extending the central part of Melbourne to places such as Bendigo and Castlemaine. The large geographic spread of the Brisbane-Gold Coast city region is driven by beach resources and amusement parks.

Are city-regions viable?

Good infrastructure connections, economic cooperation, and institutional integration all make city-regions successful.

At the core of these factors is the willingness and capacity to cooperate among individuals, industry, and local governments. A healthy city-region future will depend on both strategic visions which are shared by individuals, communities, business and governments, and sound infrastructure networks that enable the easy movement of people, goods and ideas. Planners are key professionals who contribute to the provision and management of infrastructure, land, the environment, and urban policies.

Forward-looking planning efforts for infrastructure provision, institutional reforms, and ecological standards are instrumental to remaking our society and environment when creating healthy future city-regions.

What we gain when a city-region expands

The spread of city-regions is an unstoppable trend. City-regions are footprints of socioeconomic processes. Their growth creates required space for the expansion of population and economy.

When we experience the expansion of urban areas into global city-regions, we gain positive opportunities to rethink and restructure the relationship between the built and the natural environment and reform our governance structures.

Importantly, the growth of city-regions generates projects and jobs, positively contributing to the broader economy. With proper planning and management, the negative consequences of city-region development can be contained.

The challenge for planners is to understand the nature of the city-regions; to innovate planning and policy processes and outcomes. We can tap the material benefits of city-region development while managing the socioeconomic and ecological consequences effectively.

Several countries aim to invest in infrastructure that will facilitate the growth of 'city-regions'. In the USA, America 2050 has identified 11 mega-regions (another word for city-regions); in China, seven giant urban agglomerations are defined in the national urban development plan based on more than 20 existing and emerging city-regions.

Political power in city-regions

The growth of city-regions presents both threats and opportunities to the state.

One of the main threats observed in emerging economies is the diseconomy of scale. In the Beijing-Tianjin-Hebei city-region in China, for example, the increasing connectedness of these already huge urban areas has generated great demand for road infrastructure, better environmental coordination, reform of compartmentalised policies and regulations, and economic restructuring. The central state's ability to manage such an urban giant is being tested.

On this shifting ground, new alliances, pursuing economic, environment and social goals, have the power to weaken existing state-local power relations.

It may be hard to imagine under the existing governance structure in China, but the potential increase in the power of 'city-regions' in future political negotiations (especially in relation to state dominance) cannot be underestimated. Huge 'city-regions' with multiple cities will have the chance to restructure and perform at a level far beyond a simple summation of individual cities.

Small city states such as Singapore and Hong Kong are not, themselves, city-regions. They make up a part of city-regions in their respective territories. The Singapore-Johor-Riau Growth Triangle is indicative of a political vision for the cross-border development of city-regions.

The concept was popularly discussed in the late 1990s but substantial progress was inadequate, largely due to the lack of consensus between the governments concerned. Hong Kong's integration into the Pan Pearl River Delta has faced difficulties too, although decentralisation in the city-region is occurring. Competition among local governments remains the main hurdle to the formation of city-regions.

The Australia/China Research Network on Planning Global City-Regions is funded by a University of Melbourne Research Network and Consortia grant.