The phrase "sustainable development" was coined by the World Commission on Environment and Development (the "Bruntland Commission") in 1987. The Commission defined "sustainable development" as material improvement to meet the needs of the present generation without compromising the ability of future generations to meet their own needs.[1] This definition emphasizes an important aspect of our ethical relationship to the unborn, yet it remains too vague to be truly useful as a guide for human activity because we cannot agree on the meaning of "needs." We can't really know what the "needs" of future generations will be, and we can't even agree on what we ourselves "need" vs. what we merely want.

Fortunately, more useful definitions of "sustainable development" are coming into focus. By "more useful" I mean definitions that will allow us to reach agreement, thus giving us a common basis for action. In his book BEYOND GROWTH,[2] economist Herman Daly defines "sustainable development" as "development without growth -- without growth in throughput beyond environmental regenerative and absorptive capacity."[2,pg.69] This is an important definition, worth examining.

First, let's look at "throughput." Throughput is the flow of materials and energy through the human economy. It includes everything we make and do. When we speak of "growth" we are talking about growth in throughput -- people making (and throwing away) more stuff and using more energy to do it. The totality of the human economy is throughput. It is calculated as the total number of people multiplied by their consumption.

The "regenerative and absorptive capacity of the environment" refers to the ability of the environment to provide (a) materials for our use, and (b) places where we can throw our wastes. This gets a little more complicated. It refers to two things -- (1) the ability of the environment to provide us with the high-quality raw materials we need to make things, and (2) the ability of the environment to break down our wastes and turn them back into raw materials, an essential service.

Let's take waste first. When we throw things away, nature begins to take them apart and recycle them. For example, when we throw away wood, natural agents (called "decomposers"), such as termites, begin to eat our wood waste and break it down into raw materials -- carbon, hydrogen, oxygen, nitrogen, sulfur, and so forth. Creatures such as earth worms use the termites' wastes as raw materials for soil, which provides nutrients for new trees to grow. This is called the "detritus food chain" and it is essential to life on earth, though largely invisible from a human perspective. The detritus food chain is made up of insects, bacteria, funguses, and other creatures that most of us know little about. But without their workings, the world would become overloaded with wastes and biological processes would become clogged and stop working.[3] If you've ever visited a modern hog farm, you have an idea of what it means to exceed the capacity of the local environment to absorb waste. It is unpleasant and hazardous.

A second major benefit that nature provides for us is high-quality raw materials that we can use. Herman Daly calls these "natural capital," of which there are two kinds. The first kind of natural capital takes the form of a stock, a fixed quantity, such as oil or coal or rich deposits of copper. We can use these stocks of natural capital at any rate we choose, but when they are used up (dispersed into the environment as wastes), they will no longer be available for our use, or for the use of future generations. (The second law of thermodynamics guarantees that we can never take highly-dispersed atoms of, say, copper and gather them back into a highly-concentrated copper deposit. The energy requirements of such an operation are simply too great. If the second law didn't hold true, as Herman Daly says, we could make windmills out of beach sand and use them to power machines to extract gold from seawater. Unfortunately, the second law DOES hold true, and once we disperse highly-concentrated ores, we cannot afford to reconcentrate them.)

The second kind of natural capital takes the form of a flow. In general these flows are continuous (though human bungling can interrupt some of them). Examples include sunlight, the capacity of green plants to create carbohydrates by photosynthesis, rainfall, and the production of fish in the oceans. These forms of natural capital are endlessly renewable but can only be used at a certain rate -- the rate at which nature provides them. Example: So long as we cut trees at a certain rate, and no faster, then nature will produce new trees fast enough to maintain a constant supply of cuttable trees. If we cut trees faster than that, nature will not be able to keep up with us and then people in the future will have fewer trees to meet their needs. The capacity of the Earth to support life will have been diminished. This is an example of exceeding the capacity of the ecosystem to regenerate itself.

Growth, then, means quantitative increase in physical size. Development, on the other hand, means qualitative change, realization of potentialities, transition to a fuller or better state. On a planet such as Earth, which is finite and not growing, there can be no such thing as "sustainable growth" because growth will inevitably hit physical limits. Because of physical limits, growth of throughput is simply not sustainable indefinitely. But development CAN continue endlessly as we seek to improve the quality of life for humans and for the other creatures with which we share the planet.

To repeat, then, sustainable development means development without growth in throughpout that exceeds the regenerative and absorptive capacity of the environment. Sustainable development and the standard ideology of growth stand in contrast to each other and, in fact, are incompatible with each other.

Thus to be sustainable, the human economy (our throughput) must not exceed a certain size in relation to the global ecosystem because it will start to diminish the capacity of the planet to support humans (and other creatures). If the human economy grows too large, it begins to interfere with the natural services that support all life -- services such as photosynthesis, pollination, purification of air and water, maintenance of climate, filtering of excessive ultraviolet radiation, recycling of wastes, and so forth. Growth beyond that point will produce negative consequences that exceed the benefits of increased throughput.

There is considerable evidence that the throughput of some parts of the human economy has already exceeded the regenerative and absorptive capacity of the environment. The problem of climate change and global warming is an example; it provides evidence that we have exceeded the capacity of the atmosphere to absorb our carbon dioxide, methane, and nitrogen oxide wastes. Many of the fresh water fish of the world now contain dangerously elevated levels of toxic mercury because we humans have doubled the amount of mercury normally present in the atmosphere -- evidence that we have exceeded earth's capacity to absorb our mercury wastes.[4] Depletion of the ozone layer is evidence that we have exceeded the atmosphere's capacity to absorb our chlorinated fluorocarbon (CFC) wastes. This list can readily be extended.

There is also considerable evidence that we have already diminished several important stocks and flows of natural capital. The U.S. economy, for example, is now dependent upon oil imported from the Middle East because we have depleted our own stocks of oil. Most of the world's seventeen marine fisheries are badly depleted -- a flow of natural capital that we have overharvested, in some cases nearly to the point of extinction. (See REHW #587.) This list, too, can readily be extended.

One particular limit seems worth noting at this point. In 1986, a group of biologists at Stanford University analyzed the total amount of photosynthetic activity on all the available land on Earth, and asked what proportion of it have humans now appropriated for their own use (mainly through agriculture)?[5] The answer is 40%. This leaves 60% for the use of non-humans. But the human population is presently doubling every 35 or 40 years. After one more doubling, humans will be using 80% of all the products of sunlight, and shortly after that, 100%. Don't get me wrong -- humans are important. But I don't know very many people who think it would be smart to deny every wild creature access to the basic food and habitat resources of the planet just to keep the human economy expanding. Even if we thought we had the right to use 100% of the green products of sunlight for our own purposes, the human population would have to stop growing at that point because there wouldn't be any more sunlight to appropriate. That time is less than one human lifetime (70 years) away.

Thus we soon will reach -- or more likely have already reached -- the point at which growth of the human economy does more harm than good. What is needed under these circumstances is to stabilize total consumption, total throughput.

There are two basic rationales for doing this, one based in science and one in religion. Herman Daly offers both. We have heard the scientific argument, above, which says that the capacity of the Earth to support life is being -- or soon will be -- diminished by growth of throughput and that sooner or later we can only hurt ourselves and our children if we persistt on this path of unsustainability. The religious argument goes like this:

"I believe that God the Creator exists now, as well as in the past and future, and is the source of our obligation to Creation, including other creatures, and especially including members of our own species who are suffering. Our ability and inclination to enrich the present at the expense of the future, and of other species, is as real and as sinful as our tendency to further enrich the wealthy at the expense of the poor. To hand back to God the gift of Creation in a degraded state capable of supporting less life, less abundantly, and for a shorter future, is surely a sin. If it is a sin to kill and to steal, then surely it is a sin to destroy carrying capacity -- the capacity of the earth to support life now and in the future. Sometimes we find ourselves in an impasse in which sins are unavoidable. We may sometimes have to sacrifice future life in order to preserve present life -- but to sacrifice future life to protect present luxury and extravagance is a very different matter."[2,pgs.222-223.]

--Peter Montague
(National Writers Union, UAW Local 1981/AFL-CIO)

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1. Gro Harlem Brundtland and others, OUR COMMON FUTURE (New York: Oxford University Press, 1987).

2. Herman E. Daly, BEYOND GROWTH (Boston: Beacon Press, 1996).

3. See any ecology textbook; for example, G. Tyler Miller, Jr., LIVING IN THE ENVIRONMENT Ninth Edition (Belmont, California: Wadsworth Publishing, 1996), chapter 5, "Ecosystems and How They Work."

4. F. Slemr and E. Langer, "Increase in global atmospheric concentrations of mercury inferred from measurements over the Atlantic Ocean," NATURE Vol. 355 (January 30, 1992), pgs. 434-437.

5. Peter M. Vitousek and others, "Human Appropriation of the Products of Photosynthesis," BIOSCIENCE Vol. 34, No. 6 (1986), pgs. 368-373.

Descriptor terms: growth; sustainable development; brundtland commission; world commission on environment and development; throughput; economics; herman daly; beyond growth; ecosystem functioning; detritus food chain; natural capital; development (defined);

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