What is sustainability, anyway?

• Author: Prugh, Thomas
• Position: Biosphere II and Easter Islands

Introduction

Twelve years ago this September, eight men and women said goodbye to wellwishers and walked into Biosphere II, a 3.1-acre airtight greenhouse in the Arizona desert. The door was sealed behind the "bionauts," a team of specialists right out of Mission: Impossible: a systems engineer, a physician, two biologists, agricultural scientists, a computer systems expert. They planned to remain under glass together for two years, proving that humans could design, construct, and live in a self-sufficient ecosystem.

The project got off to a good start and ran smoothly for several months. The $200-million enterprise represented years of planning and the most up-to-date research into ecosystem design and function, and the planners seemed to have thought of everything. Like the Earth ("Biosphere I"), Biosphere II was a closed system except to sunlight. It featured a productive mix of biomes, including miniature forests, lakes, streams, and even an "ocean." The researchers expected to live off the system's internal output, without additional food, oxygen, or other supplies, throughout the experiment.

In Mission: Impossible, the experts routinely encounter odds that seem impossible indeed, but the operations nevertheless always go flawlessly. Biosphere II's experts, on the other hand, were blindsided by unforeseen developments. After 18 months, oxygen concentrations had dropped from 21 percent to a marginal 14 percent, the level found at about 17,500 feet. The carbon dioxide exhaled by the bacteria-rich soils was being absorbed and bound up in the concrete walls of the building, so the plants couldn't break it down into carbon and free oxygen. Other troubles, apart from friction among the human inhabitants, included the extinction of three-quarters of the small animal species and all of the pollinating insects. Insect life in general came to be dominated by ants. Food plants grew poorly, but weedy vines ran wild. (Supplemental oxygen pumped into the greenhouse kept the crew going for the full two years.)

Biosphere II was a physical experiment in sustainability. The project scraped off all the political and rhetorical barnacles that cling to the idea of sustainability, leaving the essential question: How do we make a self-contained place to live, and keep it going for a long time? The question is important because human beings are doing many things to the planet that are, or may be, destructive to the natural systems we depend on. But scaling the question up to the full-size real world brings back the barnacles and makes the matter complex and ambiguous, because of the many "it depends" questions that must be asked: For how long? For how many people? Are they rich or poor? What are their views of other creatures? What technologies are available? and so on.

Despite its limits, the answer that came out of Biosphere II is valuable. Since it was just an experiment, it would be inaccurate to say it tailed; it simply yielded data. One of the things it showed is that ecosystems are extraordinarily complex and dynamic, poorly understood, and prone to unforeseeable behavior that may alter their functionality. (As the saying goes, ecology isn't rocket science; it's a lot harder.) These "wild facts" likewise color and inform everything that can be said about living sustainably on "Biosphere I." It's not so easy to create a robust, productive, hospitable, and long-lived life-support system, and it is very foolish to ignorantly compromise the one we've got.

Many are tempted to ignore these facts. Sustainability, despite being a relatively new term, has already been overused and corrupted. For its display at the 1992 Rio Summit, for instance, an Italian energy company chose the slogan "Sustainable Development: We're Growing With the Planet'--apparently intending no irony and without explaining in what way the planet itself was actually growing. Just as sustainability can be distorted so that it considers only humans' interests, it can also be defined in ways that force homo sapiens out of the picture altogether--as in the views of some "deep ecologists" who see people as a cancer on the Earth. Being human ourselves, the authors have a viewpoint that is centered on human values and experiences. But we have tried to strike a balance, and we argue below that to achieve true sustainability it is both necessary and right to have a proper regard for all riving creatures.

All people and cultures try to improve their lives and conditions; this process is often called development. To achieve sustainability requires sustainable development, which was most famously defined by the Brundtland Commission in 1987: roughly, the ability to meet our needs without compromising the ability of future generations to meet theirs. It's a durable definition because it is flexible and open to interpretation. An obvious flaw, however, is that it begs the question. Of course people will always need food, water, and shelter to survive, but to thrive will take more than that--and we should not presume to know, beyond certain basics, what future generations will need to thrive. All we can be reasonably sure of is that they will value having choices. Ultimately, sustainable development and sustainability itself are about collective values and related choices and are therefore a political issue, almost certainly the supreme global political issue of this century. Because values, politics, and our understanding of the Earth and its systems will evolve, notions of what is sustainable will never be static.

But we have to begin somewhere. As a big, sloppy subject, sustainability can be approached in many different, and equally legitimate, ways. It may be convenient to think about sustainability in terms of four dimensions--human survival, biodiversity, equity, and life quality (see figure). Survival refers to the bare minimum conditions required for the continued presence of the species homo sapiens on the Earth, and we start there because without species survival, the rest is moot. This is not our main focus, however, because human environmental blunders and excesses are not likely to threaten us as a species. More important are the remaining three elements, which contribute to our survival as a species out also encompass me survival of humans as communities of individuals, as well as the forms of human welfare we pursue--freedom, fairness, fulfillment, and related ideas--after we're reasonably assured of survival. We make this distinction because history offers many examples of human cultures that were hardly fair or just but still managed to last a long time.

The four dimensions are arranged in a layered pyramid that resembles psychologist Abraham Maslow's hierarchy of needs. The idea is much the same: the dimensions are addressed from bottom to top and the upper layers build on the ones below. We end by briefly describing a tore strategy for moving toward a culture of sustainability.

Human Survival

In the sci-fi film The Matrix, intelligent machines have bumped human beings off their self-assigned place at the pinnacle of creation and turned them into dream-pacified energy slaves. The Matrix Reloaded, the sequel, ends with the machines boring rapidly toward the underground city of Zion, the last refuge of the few human rebels against the new world order. Things look bad for the humans. (The final episode is set for release in late 2003.)

Is this scenario plausible as The End?

Something, if not smart machines, will no doubt kill off humanity sooner or later. The fossil record suggests that no species lasts very long in geological terms (although the humble cockroach, already 280 million years old, may prove the exception). A likely assassin is an asteroid or comet, such as the one that apparently collided with the Earth and wiped out the dinosaurs 65 million years ago.

Killer asteroids or parricidal robots seem more plausible than species-cide. Doomsday literature has traditionally fingered nuclear holocaust, runaway viruses, or environmental crisis as likely ways we might kill ourselves off. But humans (like cockroaches) have proven so resilient and adaptable that we have moved into nearly every place on Earth except the oceans. And although biologists have long debated the minimum population needed to sustain a vertebrate species for a few hundred years, the closest

thing to a standard estimate is the low thousands. Given this relatively low number, and the adaptability and geographic dispersal of human beings, it's hard to imagine that even the horrors just mentioned would do more than trigger a massive eclipse of the human presence on the Earth.

So human survival as a species does not seem to be in much danger from anything we might do to the global ecosystem, however rapacious, stupid, and/or short-sighted. Nevertheless, the survival of billions of individuals certainly is. From a strictly anthropocentric point of view, the only human survival issue that concerns sustainability is that such rapacious, stupid, and/or shortsighted abuse of our environment will kill many people, cause profound suffering, and devastate cultures.

The human survival dimension of sustainability thus boils down to the question, How many people can the Earth support? This is also the title of a rich and wide-ranging book by Rockefeller University biologist Joel E. Cohen, who notes that people have been making such estimates for nearly 400 years, with results that range from less than 1 billion to more than 1 trillion. Clearly, there is no simple answer except "It depends." According to Cohen, it depends on:

* the typical level of material well-being;

* the distribution of material well-being;

* available technology;

* political institutions;

* economic arrangements;

* demographic arrangements;

* physical, chemical, and biological environments;

* how much variability in total population is acceptable;

* peoples' willingness to risk local ecological disaster;

* the...