martes, 12 de mayo de 2015

Environmental encyclical: what is “sustainability”?

What Does “Sustainability” Really Mean?

by William M. Briggs

The Pontifical Academy for Science’s summary of their recent conference on sustainability, itself anticipating our Holy Father’s (supposed) environmental encyclical, is suffused with scientific inaccuracies, some small, others large. But these are forgivable, considering the hearts of its authors are in the right place; and perhaps the theology of the document is sound.

The PAS said, “Unsustainable consumption coupled with a record human population and the uses of inappropriate technologies are causally linked with the destruction of the world’s sustainability and resilience.” What is “sustainability”?

If a resource is limited, in the sense of it being finite and non-renewable, then any use of it whatsoever diminishes its stock and makes that part of it unavailable to others. Thus any use of a truly non-renewable resource is by definition unsustainable. With one proviso, if used at any rate greater than zero, it must eventually be depleted.

Now non-renewable means that which cannot be renewed. All resources on this planet are finite, because the earth is finite, and so everything is unsustainable given sufficient time. “For the sword outwears its sheath…” But some resources are finitely renewable in the sense that the resource can be used repeatedly, like aluminum in cans. And other resources are plainly non-renewable, such as coal and crude oil. Once they are used up, they are gone forevermore.

  • The Effect Of People

Enter the proviso. Any use of a non-renewable is unsustainable if the number of expected future people exceeds the per-person consumption rate. Suppose on average each person uses one gallon of oil per day. There are around seven billion people alive today. Assuming a steady population, over the next year these people will use around three trillion gallons of oil. If we estimate the stock of oil at one thousand trillion gallons, and if these (mostly fictional) numbers were to hold steady, then we’d have about three centuries of oil left.

The calculation is complicated. To decide if a non-renewable resource is unsustainable depends on how much of it there is, the changing rate of its use, and the number of people expected in the future. It also hinges on whether the non-renewable will remain non-renewable, that a substitute for the non-renewable will not be discovered, and that the effect caused by use of the non-renewable will always be desired. We must know all these things, else the point at which we run out of the non-renewable will be unknown. If we do not know all these things, it is wrong to claim use of a resource is “unsustainable.” Let’s take each item in turn.

There are tremendous uncertainties in estimates of non-renewable stockpiles. How much crude oil is left? There are many widely varying answers, but no consensus. How much uranium? How much coal? How many rare earth minerals? How much of some other substance which is not now seen as important but which, after some technological change or cultural innovation, will become crucial? All great questions, and all with wide plus-or-minus bounds.

The rate at which a thing is used depends on the number of people using it, which itself depends on culture and politics and the state of technology. We can form reasonable but imperfect guesses of consumption for the here-and-now, but forecasting use is fraught with danger. Even supposing a fixed population, no serious student of history can be comfortable projecting shifts in culture, and only the foolish are sure of what lies ahead technologically. Technology can change so that the resource used is needed more or needed less to produce the same effects, or technology can lead to the discovery of substitutes for the resource’s effects. Or the effects themselves—and this falls under culture—can be seen as less or more desirable.

We enjoy lighting in our abodes but no longer employ whale oil for this effect. This non-renewable resource would have been depleted given the population rise since 1900 and the increased demand for the effect. But—much of the increase in the demand was caused by the improving technology and the substitution of electricity. Nobody in 1900 came remotely close to predicting these changes. Who can say with any certainty what effects people a century hence will demand or how the effects demanded will be produced?

  • Are People Good Or Bad? ...
  • How Many Of Us? ...
  • Cultural Hubris ...
  • Incompatible Weltanschauung ...


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