looking back to the future

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Looking Back to the FutureAuthor(s): Will SteffenSource: AMBIO: A Journal of the Human Environment, 37(sp14):507-513. 2008.Published By: Royal Swedish Academy of SciencesDOI: http://dx.doi.org/10.1579/0044-7447-37.sp14.507URL: http://www.bioone.org/doi/full/10.1579/0044-7447-37.sp14.507

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Will Steffen

Looking Back to the Future

The emergence of climate change as a central politicalissue around the world, along with growing concern forthe environment more generally, has raised the challengeto achieve sustainability as a high order social goal. Yetover the 20 y since the publication of the landmarkBrundtland Report on sustainable development, humanityhas moved further away from sustainability in manyimportant aspects, particularly at the global scale. Thispaper provides an overview of the current understandingof how the human-environment relationship has evolvedthrough time, analyzes the quest for sustainability incontemporary society, and briefly explores the implica-tions of these analyses for the trajectory of the human-environment relationship in the twenty-first century. Thefocus is on an Earth systems perspective. Exploration ofthe human-environment relationship through time showsa fundamental switch about 200 y ago, when humansociety shifted from being largely the recipient of changesin Earth system functioning to becoming a globalgeophysical force itself, rivaling the great forces of naturein magnitude. Contemporary human societies are now ona demonstrably nonsustainable trajectory, especially withregard to climate change, with no sign at the global scale

of any change in trajectory. An analysis of the sustain-ability gap suggests that a crucial missing component inour quest for sustainability is a failure to engage thehumanities, along with the biophysical and social scienc-es, economics, and technology, in the search for solu-tions. An examination of the ways in which pastcivilizations have responded to external stresses andthe analysis of the contemporary sustainability gap havecome to the same conclusion. Those societies thatrespond to environmental and other stresses by trans-formation rather than collapse have the capability toquestion their core values if they become dysfunctionaland to drive fundamental shifts in those values, leading tomore adaptive and resilient societies.

THE LONG-TERM RELATIONSHIP BETWEEN

HUMANS AND THE ENVIRONMENT

The advent of climate change as a central political issue invirtually all corners of the world has signaled the emergence ofthe environment more generally as a major concern of society inthe twenty-first century. Other aspects of environmental

Photo: His Majesty King Carl XVI Gustaf of Sweden.

Ambio Special Report 14, November 2008 507� Royal Swedish Academy of Sciences 2008http://www.ambio.kva.se

change—pressure on water resources, loss of biological diversity,land degradation, overfishing of the oceans, and so on—are alsorising in the political agenda as issues that need to be dealt witheffectively. Taken together, these global environmental trends,as well as a suite of closely related global socioeconomic trends,raise the challenge of sustainable development (1). How cancontemporary high-growth, high-tech, high-consumption socie-ties achieve a long-term sustainable relationship with theenvironment that ultimately sustains them?

Possible approaches to meeting the challenge of sustainabledevelopment are being discussed and debated today, but mostare grounded in the dynamics, values, and structures ofcontemporary societies, leading to various trajectories into thefuture. Much can be learned, however, from exploring the waysin which past societies and civilizations have interacted with theenvironment, a rapidly growing area of scholarship (2–6). Theaim of this paper is to i) provide an overview of the currentunderstanding of how the human-environment relationship hasevolved through time, ii) analyze the quest for sustainability incontemporary society, and iii) briefly explore the implicationsof these analyses for the trajectory of the human-environmentrelationship in the twenty-first century. In particular, the focuswill be on the global-scale aspects of the human-environmentrelationship, viewed through the lens of Earth system science(7, 8).

From the appearance of fully modern humans in Africaabout 250 000 y ago, the rhythms of the Earth system have been

a strongly defining parameter in the development and move-ment of our species until very recent times (9). The firstsuccessful migration of humans out of Africa occurred about85 000 y ago, during an intense cold period when sea level waslower and a passage around the southern end of the Red Seainto the Arabian peninsula was possible. Our ancestorscontinued along the exposed continental shelves of South Asiaand spread through Southeast Asia and the Indonesianarchipelago, which was much more connected than it is today.The first wave of migration out of Africa eventually endedabout 65 000 y ago in Australia.

As humans spread from this initial migratory pathway intoEurope, Asia, and, later, into the Americas (9), they interactedwith new and different environments. Although still hunter-gatherers, our ancestors had considerable environmental impactat the local and even the continental scales, primarily throughthe use of fire to modify vegetation and aid in the hunt (10) andthrough the direct hunting pressure exerted on large fauna inNorth America, Australia, and Asia (11–13). There were not,however, any significant impacts of human activities at theglobal scale. These interactions of humans with their environ-ment operated largely on local and regional—and sometimescontinental—scales. There is no evidence that human use of fireor that the extinction of megafauna on three continents had anydiscernible influence on the functioning of the Earth system,either via the climate or through the cycling of elements such ascarbon, nitrogen, or phosphorus through the system (6).

With the advent of agriculture about 10 000 y ago, thehuman-environment relationship changed in fundamental ways.Humans could now convert terrestrial ecosystems into new,

Figure 1. Three cases of the interaction of preindustrial humancivilizations with the environment (14–16). In each case thetransition of the regional climate into much drier conditions is wellcorrelated with the deterioration or collapse of the civilization.

The near-complete conversion of a terrestrial ecosystem into anindustrialized landscape (Photo B. Prechtel of ARS-USDA).

508 Ambio Special Report 14, November 2008� Royal Swedish Academy of Sciences 2008http://www.ambio.kva.se

managed systems. When this involved the clearing of forests tocreate managed grasslands or croplands, carbon was released tothe atmosphere. Management of the new ecosystems alsomodified the flows of elements, at least at local and regionalscales. But, again, there is no indisputable evidence that theadvent of agriculture had any discernible effects on thefunctioning of the Earth system (6).

Thus, until very recently in the history of our species, thehuman-environment relationship was very much a one-wayaffair, at least at the global scale. Early civilizations did notaffect the functioning of the Earth system, but the vagaries ofEarth system dynamics, often manifested as large-scale patternsof climate variability, at times had devastating impacts on them.Figure 1 shows three examples where shifts in the climate systemled to extended dry periods in various regions of the planet. Ineach of these cases, a civilization that had existed in the regionfor centuries was unable to cope and collapsed (14–16).

It is critical to note, however, that these cases were certainlynot simple examples of environmental determinism. Variousexplanations have been developed to describe how societies,through their own internal structures and dynamics, maybecome more or less vulnerable to external shocks or stresses,including environmental change. These explanations include therole of complexity in conferring resilience or vulnerability (17),the inflexibility of core societal values (3), and the distortion ofnetworks of trade and communication by centralization (18).These analyses have important lessons for the interaction ofcontemporary human societies with the environment, as will bediscussed later in the paper.

For now, the fundamental point is that however humansinteracted with the environment, and however they respondedto environmental change and stress, they were not capable ofinfluencing the functioning of the Earth system at the globalscale.

TURNING THE TABLES ON NATURE

As we proceed further into the twenty-first century, it isincreasingly obvious that homo sapiens has turned the tables onnature. The escalating human impact on the global environmentis now well documented (8). Over 40% of the Earth’s landsurface is now fully dominated by humans, and much of the restis significantly influenced by our activities. Industrial processesnow fix more nitrogen from the atmosphere than all naturalterrestrial processes combined. The Earth is now in the midst ofits sixth great extinction event, but the first one largely causedby a single biological species—homo sapiens. The case thathumans are now driving the clearly observable rapid warmingof the global climate is now beyond doubt (19). The list could goon and on. The point is that the relationship between humansand the rest of nature has fundamentally changed. We nowrival, or sometimes exceed, the great forces of nature in ourimpact on the Earth’s life-support system at the global scale.

Many other important features of the human-environmentrelationship have also changed significantly, many of them onthe socioeconomic side of the equation (20). For example, in thepast humans could solve environmental (or other) problems bymoving to a new, pristine location. Now virtually everyhabitable corner of the planet is occupied, so there are veryfew options for humans to move into unoccupied locations. Inaddition, this vastly distributed human population is now muchmore connected than it has ever been before, largely due to therevolution in electronic communication. Information, capital,goods, and increasingly humans, are now moving around theplanet in rising quantities and at accelerating rates. Finally, thevarious global-scale changes in both the environmental andsocioeconomic spheres are occurring simultaneously and are

strongly interactive. Global change has become one of the mostdominant features of life in the twenty-first century.

A striking feature of the evolution of the human-environ-ment relationship over the past several centuries has been theremarkable increase in the rate of change of many aspects ofthis relationship following World War II (8). Often called theGreat Acceleration (21), this phenomenon is largely responsiblefor the many global-scale changes now evident in theenvironment.

Figure 2 presents a simple, stylized systems diagram of thedynamics of the Great Acceleration (21). The core process is thetight loop connecting population and consumption; in theperiod after World War II, the per capita consumptioncomponent of that loop has been the more dominant one.The importance of a well-functioning society, in particularinstitutions and political economy, is crucial for the population-consumption loop to operate effectively. The impact of thecollapse of the former Soviet Union on both its population andconsumption is a good example of the importance of this part ofthe system. But perhaps the most defining feature of the GreatAcceleration, which differentiates it from past civilizations, isthe central place that knowledge, science, and technology playas drivers and facilitators of a rapidly expanding capability toimprove human health and longevity and to deliberately andpurposefully manipulate the rest of the natural world aroundus. This is unprecedented in the history of Earth.

The Great Acceleration has dramatically altered the rela-tionship between humans and the rest of nature, primarilythrough the phenomena of globalization and urbanization, aswell as through the changes in governance and institutions thathave occurred in the past several decades (20, 21):

Globalization.– Globalization has had mixed environmental impacts at local

levels; in some cases heavily polluting industries haverelocated to countries or regions with low environmentalregulatory standards, but in other cases more responsibletransnational companies have imposed their own highenvironmental standards on local operations. At theplanetary scale, globalization has largely led to the homog-enization of the environment, with similar productionsystems and species being adopted in most parts of theworld, coupled with a loss of biological diversity nearlyeverywhere.

Figure 2. A systems diagram of the Great Acceleration, showing thecore processes that drive the phenomenon (red), the critical roleplayed by a well-functioning institutional framework (blue), and thepost-World War II importance of knowledge and technology in thedynamics of the Great Acceleration (yellow) (21).


– In general, globalization has led to a loss in the diversity ofcultural values. With the spread of the Western consumptivelifestyle around the world, human societies are becomingmore similar. There is also some concern about the future oflanguages that do not have large numbers of speakers, asEnglish and Spanish—and perhaps Mandarin in the twenty-first century—become dominant global languages.

– In some developing countries, globalization has triggered adebt crisis as societies consume newly available goodsbeyond their long-term capacity to pay for them. A commonapproach to address a debt crisis is to liquidate environ-mental assets in the short term.

Urbanization.– The rapidly increasing proportion of the world’s population

that live in urban areas, and particularly in megacities,highlights the different experiences and understanding ofnature of urban dwellers compared to people living in ruralareas. Urban dwellers generally have a higher level ofeducation and thus have a better understanding of ecologyand environment, at least in theory, than do rural dwellers.However, people who live in rural areas generally have abetter understanding of the practical side of ecology and theenvironment, with much better insights into the ways inwhich humans extract important goods and services from thenatural environment.

– When people move from rural areas into cities, they have anexpectation of rising consumption and, through generallyincreasing wealth compared to rural dwellers, they also havean increased capacity to consume.

– The linkage between rural and urban regions has changeddramatically through the Great Acceleration. The goods andservices on which cities depend are increasingly accessedfrom far-flung places around the world rather than from theimmediate hinterland around the city. Urban dwellers areoften unaware of the places from which their goods come(food is a good example), the ecosystem services required toobtain them, the social conditions under which they wereproduced, or the carbon costs required to get them from theplace of production to the place of consumption. Theconcept of urban footprints is a powerful way to conceptu-alize the unseen, often unrecognized, but utterly crucialdependence of urban regions on ecosystem services.

Governance.– Since the Second World War, there has been a shift to free-

market economic systems around the world. With thecollapse of the Soviet Union in 1990 and the adoption of alargely free-market economy in China, this process isvirtually complete. Free-market economic systems havesome significant challenges in dealing with environmentalexternalities; recent attempts to price some ecosystemservices and move them within the economic system haveled to some environmental improvements.

– Traditionally environmental management and stewardshipwas the remit of the public sector and often of centralgovernments. Decentralization and privatization of environ-mental management has become more common over the pastfew decades. While this trend has led to some positiveenvironmental outcomes at largely local scales, it hasarguably produced a diminished capacity to deal with globalenvironmental problems. A good example is climate change,which has thrown the spotlight on both the need for aninternational framework for dealing with a clearly global-scale problem and on the significant inadequacies ofdecentralized and privatized environmental managementsystems to meet this challenge.

THE UNCERTAIN QUEST FOR GLOBALSUSTAINABILITY

As introduced in the first section, the recognition that humanactivities are driving global-scale environmental changes as wellas the ongoing challenge to raise large segments of the humanpopulation out of poverty led to the concept of sustainabledevelopment. The publication of the Brundtland Report in 1987(1) signaled the emergence of sustainable development as a highlevel social goal, similar to democracy and human rights. Theconcept of sustainable development or sustainability has beenresearched at depth around the world, has been written intolegislation in jurisdictions across the planet, and has beenoperationalized in myriads of ways in many localities.

While there is no doubt that concrete steps towardsustainability, no matter how it is defined or measured, havebeen taken in many places, these almost invariably have hadeffects at local or regional scales only. The unequivocal evidencethat human activities are now rivaling many geophysicalprocesses in their influence on the functioning of the Earthsystem has raised the issue of sustainability at the global scale.Can it be achieved using the same approaches that are havingsome effect at local scales? Are we making demonstrableprogress toward global sustainability?

Climate change is a good test case for global sustainability.The problem is truly global, we have good indicators of keyparameters that characterize the problem (e.g., atmosphericcarbon dioxide concentration and global mean temperature),and we are now on what is almost universally accepted as anunsustainable pathway. Have 20 y of development of thesustainability concept and its application had any impact at allon the climate change problem?

The evidence is not encouraging. Over the past 20 y theconcentration of carbon dioxide in the atmosphere hasinexorably risen, and its rate of increase has accelerated since2000 despite a growing number of actions to reduce emissions.In fact, the trajectory of atmospheric carbon dioxide concen-tration is now tracking at or near the highest of theIntergovernmental Panel on Climate Change (IPCC) scenarios(22). As might be expected, the trajectories of global meantemperature and of sea level over the past two decades have alsotracked at or near the upper ranges of the IPCC projections(23).

The next decade will be a turning point for humanity in thechallenge to meet global sustainability. In just the last year ortwo, the possibility that human-driven climate change mightpropel the Earth system past two large geophysical tippingpoints has become more prominent in the research community.One tipping point is related to the stability of the large ice sheetsin Antarctica and Greenland, which together could raise globalsea level by 60–70 m if they disappear. Earlier thought dismissedthe possibility that anthropogenic climate change coulddestabilize these ice sheets. However, a flurry of recentobservations and research has uncovered signs of surprisinglyrapid and pervasive melting and disintegration around theperimeter of the Greenland ice sheet, raising questions of itslong-term stability and of the potential for rapid andwidespread disintegration. The second tipping point is relatedto the behavior of the terrestrial and marine carbon sinks, whichremove half of the anthropogenic emissions of carbon dioxideto the atmosphere. Recent analyses suggest that the strength ofthese sinks is weakening (24) and that the terrestrial sink, atleast, could collapse later this century and turn into a net sourceof carbon dioxide to the atmosphere (25). This second tippingpoint raises the possibility of a rapid and uncontrollable surgein global temperature (and associated changes in climate) laterthis century and beyond.


As these new data and understanding are absorbed into thepolicy community, governments are grappling with the designand implementation of a post-Kyoto international frameworkfor dealing with climate change. Although there are encourag-ing signs that many governments, the private sector, and civilsociety recognize that deep cuts of 60–80% in emissions arerequired by midcentury or a little later, the new institutionalframeworks, economic instruments, technologies, and behav-ioral changes required to achieve these cuts will be much harderto encourage, design, and implement. The international natureof the challenge and the required solutions is especiallychallenging.

Climate change is not the only challenge in the quest forglobal sustainability. In fact, it can be viewed as one of severalcritical, related problems associated with transforming thehuman-environment relationship in the twenty-first century.The Millennium Ecosystem Assessment (MEA) (26) examined24 important ecosystem services on which humanity depend andconcluded that over half of them are already degraded or beingused unsustainably. The MEA concluded that this situation canbe reversed in the twenty-first century, but such a turnaroundwill require substantial changes in values, institutions, andgovernance that are not yet underway.

The continuing loss of biodiversity is another example of thefailure of contemporary society to move toward sustainability.Current extinction rates are 100 to 1000 times backgroundlevels, and from 10% to 30% of all mammal, bird, andamphibian species are threatened with extinction this century(26). If climate change continues to track on the highest of theIPCC projections, these figures will need to be revised upward.As for climate change, there is as yet no clear evidence thateffective international measures are in place or are beingdeveloped to significantly reduce the global rate of biodiversityloss.

LOST VALUES AND MISSING SCHOLARSHIP?

The examples described above suggest that contemporarysociety is moving away from global sustainability rather thantoward it in many important ways. A recent analysis (27)examined the question of why this was the case, given the longperiod since the publication of the Brundtland Report and thehigh profile that the concept of sustainability has achievedthroughout the world.

The analysis is based on the concept of a sustainability gap,as shown diagrammatically in Figure 3. The first step in theanalysis is to define a sustainability target—a quantitative goalin a key parameter related to sustainability. The best current

example of such a target is the desired level of carbon dioxideconcentration in the atmosphere. Although a target of ultimatecarbon dioxide concentration can be set, observed, andmonitored, agreement on just what that target should be isnot a trivial task. Biophysical science has an important role toplay in informing a realistic target (and for other indicatorsdirectly related to the functioning of the Earth system), butultimately society must make a judgment on what it considers tobe ‘‘dangerous climate change,’’ which brings social, cultural,and economic factors into the equation. At present we are farfrom having a global consensus on what the target should be forstabilizing carbon dioxide concentration in the atmosphere,reflecting the wide range of opinion on what constitutesdangerous climate change.

Once a target is established, the trajectory (or trajectories)that must be followed to reach the target can be defined. Thedifference between the current trajectory and the trajectoryrequired to reach the target can be termed the sustainabilitygap. In terms of the climate change issue, the current trajectoryof carbon dioxide emissions is much higher than any realisticstabilization trajectory, yielding a very large carbon gap. Insome cases, as depicted in Figure 3, the current trajectory mayhave already moved beyond the target, and an overshootcondition is apparent. In virtually all cases where the currenttrajectory is strongly nonsustainable, there will necessarily be aperiod of time while the current trajectory is slowed and thenturned around to approach the target from above.

Changing a current trajectory significantly is the mostchallenging feature in actually achieving sustainability. Whilethe biophysical sciences are important in setting the target, theyare relatively less important in achieving it; here social sciences,economics, and engineering come to the fore. Although muchemphasis is often placed on technologies and economicinstruments, design effective institutions and governancesystems—adaptive, flexible, and resilient—are arguably moreimportant than the economic and technical aspects.

Despite our wealth of knowledge in the biophysical sciences,social sciences, economics, and technology, we are clearlymoving away from sustainability at the global scale, and inmany cases at local and regional scale as well. What is missing?The sustainability gap analysis suggested that long-term andfoundational issues need to be examined to identify the valuesand the types of institutions required to reach sustainability(27). What are long-term and foundational issues and how dowe examine them?

Figure 3. Conceptual framework summarizing the sustainabilitychallenge (27).

Figure 4. Conceptualization of sustainability, based on a hierarchicalrather than a triple bottom-line approach (27, modified from 28).


Long-term and foundational issues are the values, beliefs,motivations, and resulting behaviors needed to ensure thatpolicy and management actions are effective and appropriate tomove society toward sustainability and not away from it. Theyare critical in informing the design and construction of adaptiveinstitutions and economic instruments and in linking short-termactions with long-term goals, and they become more importantwhen an Earth system perspective is central. The missingscholarship that underpins consideration of long-term andfoundational resides in the humanities. The most importantdisciplines or ‘‘interdisciplines’’ that are often missing fromsustainability research and its applications include history,philosophy, anthropology, human ecology, and environmentallaw and politics. The critical questions that they addresstypically concern the relationship of humans to the rest ofnature, for example, humans as conquerors of nature orhumans as part of a larger biotic whole. The challenge is tomove the humanities from marginal to sustainability to centralto sustainability.

An example of how more fundamental thinking can informthe sustainability challenge is show in Figure 4 (27, 28). Thenotion that economic, environmental, and social goals need tobe balanced to achieve sustainability—the so-called triplebottom line—has achieved widespread acceptance and hasperhaps even become dogma in the quest for sustainability. Yet,particularly at the global scale and from an Earth systemperspective, biosphysical, social, and economic considerationsare not necessarily equivalent and tradable, but rather representa nested hierarchy. Without a functioning life-support system,societies cannot thrive; without functioning social structuresand institutions, economies cannot flourish. Such analyses arecrucial in setting priorities for actions to achieve sustainabilityand for informing the types of institutions and instrumentsneeded to turn around nonsustainable trajectories.

POSSIBLE FUTURES

A plethora of scenarios now exist projecting the future ofhumanity and the planet through the rest of this century and

occasionally beyond. They range from highly optimisticscenarios where sustainability has been achieved, poverty haslargely been eradicated, and humans live in harmony with eachand the rest of nature to scenarios dominated by increasinginequality, conflict, and at last partial ecological and societalcollapse. Perhaps the most well-known scenario set is that of theIPCC, which focuses on greenhouse gas emissions and climatechange but is informed by storylines that describe varyingsocioeconomic and geopolitical futures (19). The MillenniumEcosystem Assessment developed an interesting set of fourscenarios, which depict contrasting approaches to dealing withenvironmental challenges (26). The primary focus of the MEAscenarios is on ecosystem services and human well being.

Scenarios of the future have been available for nearly 20 y,and so it is possible to compare observed trajectories to thoseprojected within the scenario frameworks. As described earlier,such comparisons for the climate change issue yield some newand very fascinating perspectives. As noted earlier, we are nowtracking on or near the highest of the IPCC family ofscenarios—in emissions of carbon dioxide, in global meantemperature, and in sea-level rise. Over the past 5–10 y, not onlyhave we yet to demonstrate an ability to begin to turn aroundthese nonsustainable trajectories, but they appear to beaccelerating in the wrong direction. There is now much morediscussion of the severe end of the scenarios, which couldultimately become a question of survival or collapse, rather thanof climate change as just a troublesome externality associatedwith continued economic growth.

What does history have to tell us about our currentsituation? Although contemporary societies have pushed theEarth system into a ‘‘no-analogue state’’ (8), there is still muchwe can learn from human-environment relationships in the past.There are many examples of past societies that have collapsedunder external stress, including climatic stresses. Yet othershave transformed and thrived under similar threats. Thus,environmental change cannot only be an important factor indriving societies toward collapse, but can also be a catalyst fortransformation into more resilient societies. What are thecrucial characteristics that confer flexibility and resilience on

One of the Twin Glaciers at Akulliit.Photo: E. Kessler.


societies? What are the features of societies that allow them tochallenge their current trajectories, think creatively, and actdecisively? What are the fatal flaws that prevent societies fromexamining their core values and making fundamental change toprevent collapse?

Analyses of the responses of past civilizations to externalstress and the sustainability gap analysis described above haveall come to essentially the same conclusion. Successfully meetingthe challenges posed by major stresses cannot be done solely bytechnology or by minor changes to existing social structures orgovernance; fundamental shifts in the critical values that guidesociety, leading to changes in social structures and dynamics,are almost always required. This conclusion has significantimplications for the conduct of sustainability research andapplication in the twenty-first century. The often-forgotten areaof scholarship—the humanities—needs to become a centralfeature of the quest for sustainability.

Sustainability or collapse? The answer hangs in the balance,but it will most likely be a definitive answer. Given strongfeedback loops within human-environment systems, it is notlikely that we will muddle through tinkering with a business-as-usual approach. Rather, contemporary society will either clingto its present set of core values and reject the globalenvironmental threat as either not important enough or toocostly to address, or will rethink its core values and make as itscentral task for the twenty-first century a comprehensivetransformation of our relationship to the environment. Thenext decade is crucial. If current trajectories in climate andecosystem services do not begin to bend back toward moresustainable directions, we run the very real risk that the Earthsystem will cross biogeophysical tipping points that will force amuch more painful and destructive transformation on humansocieties.

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29. This paper has benefited greatly from the discussions with colleagues at the 2005 DahlemConference on an Integrated History and future of People on Earth (IHOPE). I am alsograteful to colleagues at the 2007 Royal Colloquium in Narsaq, Greenland, for theirinsights, and to colleagues at the Fenner School of Environment and Society, theAustralian National University, for their exploration of the sustainability gap concept.

Professor Will Steffen is Executive Director of the ANU ClimateChange Institute at the Australian National University, Can-berra, and is also Science Adviser, Department of ClimateChange, Australian Government. From July 2004 throughOctober 2005, Steffen was a Visiting Fellow, Bureau of RuralSciences, Department of Agriculture, Fisheries and Forestry,Australian Government. From 1998 to mid-2004, he served asExecutive Director of the International Geosphere-BiosphereProgramme, based in Stockholm, Sweden. His researchinterests span a broad range within the field of Earth Systemscience, with a special emphasis on terrestrial ecosysteminteractions with global change, the global carbon cycle,incorporation of human processes in Earth System modelingand analysis, and sustainability and the Earth System. Hisaddress: Australian National University, Canberra ACT 0200,Australia.E-mail: [email protected]


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