More on Carrying Capacity

From Rachel's Democracy & Health News #919, August 9, 2007

Why precaution? Because of cumulative impacts.

One of the reasons for adopting the precautionary principle, rather than the "trust in economic growth" decision rule, is "cumulative impacts."

The foundational assumption of the "trust in economic growth" rule (that economic activity is generally to the net benefit of society, even if it causes environmental damage) is further assumed to be true no matter how large our economy becomes. To implement the "trust in economic growth" rule, all we do is eliminate any activity without a net benefit, and in doing this we examine each activity independently. The surviving economic activities, and the accompanying cost-benefit- justified damage to the environment, are both thought to be able to grow forever.

Not only is there no limit to how large our economy can become, there is no limit as to how large justified environmental damage can become either. The "trust in economic growth" decision rule contains no independent constraint on the total damage we do to Earth -- indeed the core structure of this decision rule assumes that we do not need any such constraint. People who think this way see no need for the precautionary principle precisely because they see no need for the preferential avoidance of damage to the environment that it embodies.

But, as we now know, there is in fact a need for a limit to the damage we do to earth. Unfortunately, the human enterprise has now grown so large that we are running up against the limits of the Earth -- if we are not careful, we can destroy our only home. (Examples abound: global warming, thinning of Earth's ozone shield, depletion of ocean fisheries, shortages of fresh water, accelerated loss of species, and so on.)

And it is the cumulative impact of all we are doing that creates this problem. One can liken it to the famous "straw that broke the camel's back." At some point "the last straw" is added to the camel's load, its carrying capacity exceeded. Just as it would miss the larger picture to assume that since one or a few straws do not hurt the camel, straw after straw can be piled on without concern, so the "trust in economic growth" decision rule misses the larger picture by assuming that cost-benefit-justified environmental damage can grow forever.

Thus, it is the total size of our cumulative impacts that is prompting us to revisit our prevailing decision rule. This is why we now need a decision rule that leads us to contain the damage we do. It is why we now must work preferentially to avoid damage to the Earth, even if we forego some activities that would provide a net benefit if we lived in an "open" or "empty" world whose limits were not being exceeded. We can still develop economically, but we must live within the constraints imposed by Earth itself.

Ultimately, the conclusion that we must learn to live within the capacity of a fragile Earth to provide for us, painful as it is, is thrust upon us by the best science that we have -- the science that looks at the whole biosphere, senses the deep interconnections between all its parts, places us as an element of its ecology, recognizes the time scale involved in its creation and our own evolution within it, and reveals, forever incompletely, the manifold and mounting impacts that we are having upon it and ourselves.