Cities and global environmental change: exploring the links


  • Opening Plenary Session, RGS–IBG Annual Meeting, Wednesday 30 August 2006


Research into global environmental change (GEC), itself a deliberately broader and more encompassing term than climate change, has been dominated by natural sciences concerned with climate change and modelling and the processes and impacts of landuse cover change, industrialization and the like. Although industrialization is a predominantly urban phenomenon, and urban heat island effects have been known for a considerable time (Grimmond this issue), only recently has the importance of urban areas to processes of GEC been more adequately appreciated. The growing consensus that GEC is being driven predominantly by anthropogenic activities, most authoritatively exemplified by the recent Stern report on the Economics of Climate Change (Stern 2006), underscores both the need for social scientific and interdisciplinary research and the importance of an urban focus within GEC research. Raising awareness among geographers of these issues was my central purpose in organizing the plenary conference session on which this set of short papers is based.

For the first time in human history, half the world's population is now classified as living in urban areas, which are also responsible for the generation of an increasing proportion of gross geographical product in most countries. Changing international divisions of labour since the late 1970s have meant that heavy and especially ‘dirty’ industrial processes are now concentrated in poorer countries, with lower labour costs and weaker or poorly enforced environmental legislation. By the early 1990s, air quality was poorest and pollution highest in fast-growing metropolises like Shanghai, Jakarta, Bangkok, São Paulo and Mexico City, whereas traditional industrial centres in Western Europe, the USA and Japan were being cleaned up after their shift into business, producer and leisure services (Simon 1995). Changing technologies and labour costs have created several successive groups of industrializing cities, with China now accounting for an ever larger share of global manufacturing output.

While many small and intermediate cities are experiencing the most rapid rates of growth, primate and selected other large cities continue to expand in size, density and population. The number of so-called megacities, with populations of over 10 million (see Kraas this issue, footnote 1), has increased to 19, while another 22 cities worldwide are home to between 5 and 10 million people each, and 370 house 1–5 million each (Figure 1). Another 433 cities have populations between half and one million (UN-HABITAT 2006). The most rapid growth within cities, and in the number of cities in each of these size categories, is occurring in poor and middle-income countries, and at rates far in excess of the historical rates recorded in the global North.

Figure 1.

Worldwide distribution of cities by size class above one million
Source: Adapted from Fellmann et al. (2003)

Different cities, and cities with various proportions of rich, middle class and poor populations, contribute differently to resource pressures and local, national and global environmental change through their ecological and human ‘footprints’. Traditional concerns have focused disproportionately on real or perceived problems such as resource depletion, environmental degradation and pollution, overcrowding and unemployment, deficient shelter and services, infrastructural deterioration, along with alienation and violence. However, urbanization also provides benefits and opportunities. Upwards of three-quarters of future economic growth is projected to occur in cities, while they are centres of innovation, of opportunity and, in many (but certainly not all) cases, of increased quality of life. Service provision and resource use can be highly efficient under appropriate circumstances, while large cities and megacities are also crucial nodes for interventions to mitigate the effects of GEC (Sánchez-Rodríguez et al. 2005; UN-HABITAT 2006; Kraas this issue). However, as Guèye et al. (this issue) demonstrate, many urban residents are marginalized from current economic growth, sometimes directly by the effects of GEC, and are already sufficiently desperate to bale out, quite literally.

Distinguishing GEC from ‘disasters’

One abiding element of confusion about the urgency and nature of GEC is a widespread implicit or explicit perception that GEC is little different from the now well-established concern with, and research and policy literatures on, so-called ‘natural’ disasters such as earthquakes, tsunamis, hurricanes and floods (e.g. Parker and Mitchell 1995; Wisner 1997 2002 2003; International Federation of Red Cross and Red Crescent Societies 2002; Wisner et al. 2004). This line of reasoning holds that, since we now understand a great deal about such events, can often predict them and have gained substantial experience in mitigating or recovering from their impacts, we can readily apply this knowledge to GEC, perhaps with a slight increase in scale.

There is, to be sure, an overlap between the respective impacts and appropriate actions in respect of both categories of event. However, GEC is more complex and of larger magnitude. It is therefore important to distinguish them clearly (Sánchez-Rodríguez et al. 2005; Schipper and Pelling 2006). GEC comprises two distinct elements, which nevertheless reinforce each other in terms of impacts:

  • • the increasing frequency and severity of extreme events, ranging from spring tides to hurricanes and heatwaves;
  • • a range of slow-onset event or trends, like rising sea levels and increasing atmospheric temperature, of which we have long warning but which have semi-permanent or permanent impacts.

To give one specific example, not only are short-term events like storm surges becoming more severe and frequent, but they are occurring on top of a secular trend of rising sea levels that accentuate their magnitude and hence destructive potential.

Accordingly, different types and levels of response are required. ‘Disasters’ and other extreme events are mostly of short duration, ranging from a few seconds or minutes to hours or days. Therefore, the policy responses focus on forecasting, evacuation ahead of the event, and then resettlement and other post-disaster recovery. By contrast, GEC impacts are long-lasting. Hence, for example, the evacuation of people living in low-lying areas will not be for a short period of inundation but will need to be only the first stage of a comprehensive coping strategy that ultimately rehouses them away from the area likely to be (semi-)permanently inundated. Coping with GEC is therefore a long-term and far more costly challenge, which requires different ways of thinking and acting. However, already at this stage we can say with confidence – learning in part from disaster-management experience – that managed anticipation will be both cheaper and more efficient than post-hoc coping. Moreover, it is certain to provide many new opportunities and economic benefits, a generic point also underscored by the Stern Review Report (Stern 2006).

Urban areas as GEC research foci

All the above emphasizes the importance of integrating the urban arena into GEC research, policymaking and action in order to ensure integrated and ‘joined up’ approaches, and because cities, as the lynchpins of local, regional, national and international systems, are indispensable to coping strategies.

Intellectually, urban and peri-urban GEC research requires the integration of social and natural/physical scientific perspectives. Urban studies have traditionally been dominated by social scientists and perspectives that have focused on human activity and use of the environment, rather than on the environmental implications and resources themselves. However, as resource pressures and environmental stresses increase, and we begin to explore urban GEC challenges more systematically, the need for urban hydrological, geological, geomorphological, climatological, biological and engineering expertise will be increasingly appreciated. Furthermore, as Grimmond (this issue) illustrates, such collaborations will perforce be bi-directional, reflecting the environmental influences on urban activity and vice versa, just as the relationships between cities and GEC are now recognized to be bi-directional.

The foremost initiative in this respect is a 10-year programme of research on Urbanization and Global Environmental Change (UGEC), initiated in 2005 by the Bonn-based International Human Dimensions Programme on Global Environmental Change (IHDP) ( IHDP itself was founded by the International Council for Science (ICSU) and International Social Science Council (ISSC) in 1996, in order to focus on the anthropogenic nature of much GEC and to complement the strong natural scientific orientation of the longer-established programmes. Multidisciplinary collaboration characterizes all its activities. In particular, IHDP works as part of the Earth System Science Partnership (ESSP) together with the International Geosphere–Biosphere Programme (IGBP), the International Programme on Biodiversity (DIVERSITAS) and World Climate Research Programme (WCRP). IHDP does not itself fund research; instead it establishes research networks and commissions groups of specialists to formulate science plans to frame and guide the research agenda of its ‘core projects’, as the research programmes are known.

IHDP's UGEC ‘core project’

The UGEC Science Plan provides a comprehensive state-of-the-art survey of existing knowledge, dividing the literature, and identifying research lacunae, into four broad themes in order to:

  • 1analyse the bidirectionality and feedback mechanisms of the relationships between urban processes and GEC;
  • 2examine the rate, intensity and scale of urban and environmental change and mutual impacts;
  • 3establish the pathways through which urban systems are being transformed;
  • 4analyse the sustainability challenges facing urban areas;
  • 5develop appropriate conceptual frameworks and methodologies; and
  • 6collaborate with, and translate and communicate scientific results to, decision-makers, practitioners and other end-users throughout the research programme's life (Sánchez-Rodríguez et al. 2005).

Such dissemination activities are incorporated ab initio in view of their perceived importance if policy and practice are to be influenced. This marks a substantial departure from previous IHDP ‘core projects’ and most other research programmes, in which dissemination has traditionally been regarded as an activity during the final stages once the results have been finalized.

UGEC's four thematic foci are:

  • 1urban processes that contribute to GEC, with the goal of achieving an improved understanding of the underlying human and physical processes contributing to GEC;
  • 2pathways through which GEC affects the urban system, with the goal of understanding the pathways through which specific types of GEC affect local and regional processes and well-being (economic activities, livelihoods, migration patterns, human health);
  • 3interactions and responses within the urban system, in order to improve understanding of the impacts of GEC on urban systems and how the responses to these impacts within them are shaped by the interactions among its socio-economic and geopolitical processes and environmental dimensions; and
  • 4consequences of interactions within the urban system on GEC, so as to understand how the results of interactions within the urban system modify the impacts on various components of GEC (Sánchez-Rodríguez et al. 2005).

The bulk of existing research has focused on themes one and two, with theme four representing the least studied. This also constitutes the most substantial future research challenge, since it follows logically (and perhaps also chronologically) from the other themes. It is probably also the most difficult to concretize, and hence use, to influence policy processes.

Perhaps unsurprisingly, our overall knowledge is skewed in favour of certain larger metropolises in the global North, exemplified by New York, London, Tokyo and some in Australia (e.g. Bulkeley and Betsill 2003; Leichenko and Solecki 2006), which have appreciated the magnitude of likely future impacts and commissioned their own research. GEC's rise up the urban political agenda is exemplified by the announcement by Ken Livingstone, Mayor of London, on 31 October 2006 that all future transport decisions will be guided by climate change concerns (The Guardian 1 November 2006).

UGEC is adopting cross-temporal and spatial approaches and regional comparative analyses. It is building up regionally focused research networks on an inclusive basis, working outwards from the initial core groups of researchers represented by the Scientific Steering Committee, which itself has academic and NGO members with expertise in most major world regions. Researchers with existing projects that fit one or more of the UGEC themes are welcome to seek endorsement via a straightforward procedure, in order to join the network, link their project websites to that of UGEC (, and participate in relevant activities; individuals can also seek affiliate status. Aspirant grant applicants situating their applications with appropriate reference to the Science Plan can apply for a supporting letter to enhance their prospects of success, with full endorsement available once funding is obtained.

Early emerging research foci are land, carbon, water, health, energy, vulnerabilities, and integrating urban, peri-urban and relevant parts of rural areas in order to focus attention on urban processes and ‘footprints’ beyond the immediate built-up areas (Simon et al. 2006). Many of these are being investigated in collaboration with the respective other IHDP ‘core projects’ in order to foster more holistic approaches and broader multidisciplinarity.

In the following contributions, Frauke Kraas elaborates on some of the issues raised here with particular respect to megacities, while Sue Grimmond surveys current thinking on urban climate in the context of GEC, with particular reference to heat island effects, and Cheikh Guèye, Abdou Salam Fall and Serigne Mansour Tall exemplify the human impacts of GEC for particular coastal communities of the Senegalese capital, Dakar, and other cities.


Sincere thanks are due to IHDP and the RGS–IBG for sponsorship enabling Cheikh Guèye and Frauke Kraas to participate in the conference session, and to Jenny Kynaston for drawing Figure 1.