Our Common Journey: The birth of sustainability science

Fifteen years ago the National Academy of Sciences joined with George Mitchell and the Cynthia and George Mitchell Foundation to jointly produce a study entitled Our Common Journey

Our world as we saw it in 1999 was already in transition, becoming more crowded and more consuming, warmer and more stressed, more interconnected, yet diverse and divided.  Could this transition also be a sustainability transition, we wondered, one in which the many more people of the next half-century met their needs in ways that were nurturing and restoring of the planet's life support systems rather than degrading them?

Focusing on the next two generations as a critical time for humankind, we had three visions for 2050. We reasonably expected major persistent trends of population, wealth, technology, interconnectedness, and environment to continue well into the next century. These would act as the currents guiding the journey of human development. 

We also set minimal sustainability goals and needed first steps to achieve them, the realization of which to our minds would mark destinations of a successful transition toward sustainability. 

Finally, we discerned an endeavor called "sustainability science" that would be needed to navigate a sustainability transition but might also transform or propel science itself. 

But we also readily acknowledged our inability to foresee the unknowable and surprising future. 

With such uncertainty, we became advocates for adaptive management and social learning, viewing policy actions (government, corporate, or civic) as experiments designed to teach us what works, what does not work, and what works better. 

The World of 2050

We thought the world of 2050 would have about 9 billion people, 80% of whom would be living in cities, compared to the six billion in late 1999, less than half of whom lived in cities.  Population, while growing was also slowing, and completing what scholars called the demographic transition from high to low birth and death rates.  There would be an enormous challenge in feeding, nurturing, educating, housing and employing 3 billion more people in the space of a few decades. But if met successfully, this challenge was not likely to be repeated within the next century or two.

Within my own lifetime, the well being of people has substantially improved. The developing world has covered as much ground in a generation, in a material sense, as the developed economies had in a century. Yet along with growing wealth, disparities in incomes were widening at century's end. Over 800 million people were hungry and 1.3 billion were living below the poverty level of $1 a day. The gap was growing between rich and poor countries and between rich and poor people within many countries.

We also worried about consumption. As more people were adopting the consumptive lifestyle enjoyed by the industrialized nations, sustaining supplies of energy and materials, making them available where most needed, and addressing the resultant environmental problems emerged as major problems. Indeed enormous environmental changes have occurred in my lifetime. These changes, including the large-scale introduction of pollutants, a massive assault on the biota, and human-induced climate change, had no historic parallel. Humankind had begun to change the environment on a scale that equaled or exceeded that of nature itself.

Thus the future as we saw it was a wager on technology’s ability to extend the carrying capacity of the earth yet again. The emerging technologies--information, biotechnology, hydrogen, composite materials--augured well for needed changes leading to more efficient energy sources, smaller and lighter materials, and the substitution of information for energy and materials. But despite these favorable trends, the demand for products and services continued to increase and the overall consumption of energy and most materials had more than offset the gains in efficiency and productivity. Over the next two generations, technologies would be needed to more than double our capacity to make things, but in ways that did not further degrade the life support systems of earth, and all the while providing opportunities for employment.

We also saw the larger population of the future more closely connected by ties of economic production and consumption, migration, communication, and interlinked technologies, ties that were often subsumed under the rubric "globalization." But these ties did not mean that we would travel in a single spaceship earth. Our common journey we thought was launched in an armada of vessels both small and large, flying many different flags, at times hostile but in constant contact with each other, and at all times exchanging ideas, goods, and transferring passengers and crews.

A Means to a Successful Transition

Within this context, we saw an emerging three-fold definition of a successful transition: meeting human needs, reducing hunger and poverty, and preserving life-support systems.  This was a normative definition, both scientific and moral. Our science helped us to understand human needs; threats to life support systems; and how societies might not sustain themselves over the long-term with deepening divisions in well being. But to accept the burden of meeting the human development needs of unborn generations, to provide the minimal necessities to reduce hunger and poverty, and to sustain the natural world that sustained us was a moral choice for which we scientists had no special aptitude beyond our common humanity.

Fortunately for science, it was not our choice alone, but was one made repeatedly in global conferences and world summits that chose international targets to meet human needs.  These targets, some overly optimistic, did suggest that it was possible, albeit difficult, to cut hunger, child mortality, illiteracy, and the unmet needs for clean water and sanitation by half in each of the next two generations.

We identified promising objectives with which to begin. It was possible to slow population growth even further and to shift consumption to forms that were less resource depleting or environmentally degrading. Food production needed to be increased where it was needed most to accommodate the rapid population growth in Africa. The required equivalent of a thousand new and expanded cities could be built in ways that made them habitable, efficient, and environmentally-friendly. The next generation of technologies could use fewer materials and be more efficient in energy production and use. A basic global framework of protection for work and environment could make trade not only efficient but more just. The ecosystems in use over half the world needed to be managed in ways that would provide vital ecosystem services. We needed to preserve more effectively the remaining half.

For each of these promising objectives, we surely knew enough to begin to pursue them. But to follow them and the many others that would arise in the course of our common journey, and to shift direction when needed, would require a substantial expansion in the world’s capacity system for discovering new things. How might such "sustainability science" evolve?

We noted that in the last quarter of the century, four related, sometimes overlapping, but distinct research-based programs relevant to sustainability had developed:  biological research emphasizing the intertwined fates of humanity and the natural resource base on which it depends for sustenance; geophysical research focusing on the earth as a system with interconnections among the earth's climate and biogeochemical cycles, including their response to perturbation by human activities; social research, focusing on how human institutions, economics systems and beliefs shape the interactions between societies and the environment; and finally technological research, concentrating on the design of devices and systems to produce more social goods with less environmental harm.

Global Change: More Human Value, Less Environmental Damage

Already these had come together in what was loosely called "global change" science.  Sustainability science we thought, would need to be broader yet, spanning the individual branches to ask how, over the large and the long, the earth, its ecosystems and its people could interact for mutual sustenance. 

In keeping with our exploratory theme, we neither knew the paths such science would take or if indeed its ambitious rubric -- sustainability science -- would ever take hold. We did know, however, that many of the most problematic threats to people and their life support systems arose from multiple, cumulative, and interactive stresses resulting from a variety of human activities.

Sustainability science therefore had to be above all else integrative science committed to bridging both the barriers separating the traditional scientific disciplines and the sectoral distinctions between interconnected human activities. It would also need to integrate across geographic scales to eliminate the sometimes convenient but ultimately artificial distinction between global and local perspectives. In short, if there was no longer much doubt about whether integrative approaches to research were needed in support of a sustainability transition, how to achieve such integration in rigorous and useful research programs remained problematical. 

In trying to answer this question, my colleagues adopted an approach long pursued by geographers: integrating research for sustainability not around particular disciplines or sectors, but around the study of interactions in particular places.

We also thought that sustainability science needed focused research programs addressing key issues of the transition and we identified a small set of understudied questions to do so:  evaluating thresholds, critical loads, and carrying capacities for limits beyond which the life support systems of the planet should not be pushed; monitoring the many transitions then underway (population growth patterns, globalization of the economy, energy and materials intensity, and governance); exploring the determinants and alternatives to consumption patterns; identifying the incentives (markets, remedies for market failure) for promoting technical innovation that produces more human value with less environmental damage; and honing the institutions, indicator systems, and assessment tools for navigating the transition.


Dr. Robert Kates is professor emeritus at Brown University, and a senior associate at Harvard University. He co-chaired the National Academy of Sciences report Our Common Journey: A Transition toward Sustainability. He helped establish the international Initiative for Science and Technology for Sustainability, and was executive editor of Environment magazine. He was a MacArthur Fellow from 1981-85, and a recipient of the 1991 United States National Medal of Science


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