The Download of the Week is Irreversibility by Cass R. Sunstein. Here is the abstract:
The concept of "irreversibility" plays a large role in many domains, including public health, medical practice, and environmental protection. Indeed, the concept is explicit in some statements of the Precautionary Principle. But the idea of irreversibility remains poorly defined. Because of the flow of time, any loss is, in a sense, irreversible. On one approach, irreversibility might be understood as a reference to the value associated with taking precautionary steps that maintain flexibility for an uncertain future ("option value"). On another approach, irreversibility might be understood to refer to the qualitatively distinctive and even unique nature of certain losses - a point that raises a claim about incommensurability. The two conceptions fit different problems. These ideas can be applied to a wide assortment of environmental and public health questions, including overuse of antibiotics, genetic modification of food, avian flu, and climate change.
And from the paper:
The idea of option value, as used in the monetary valuation literature just discussed, is closely related to the use of the notion of “options” in the domain that I shall be emphasizing here. The simple claim is that when regulators are dealing with an irreversible loss, and when they are uncertain about the timing, magnitude, and likelihood of that loss, they should be willing to pay a sum—the option value—in order to maintain flexibility for the future. The option might not be exercised if it turns out that the loss is not a serious one. But if the option is purchased, regulators will be in a position to forestall that loss if it turns out to be large. The concern about irreversibility, and hence an Irreversible Harm Precautionary Principle, are based on the idea that regulators should be willing to buy an option to maintain their own flexibility. (I am using terms that suggest monetary payments, but the basic point holds even if we are skeptical about the use of monetary equivalents; “purchases” can take the form of precautionary steps that do not directly involve money.)
And:
It should be readily apparent how an understanding of option value might explain the emphasis, in the National Environmental Policy Act (NEPA) and other statutes involving public health and the environment, on irreversible losses. The central point of NEPA is to ensure that government officials give serious consideration to environmental factors before they take action that might threaten the environment.32 If the government is building a road through a pristine area, drilling in Alaska, or licensing a nuclear power plant, it must produce an “environmental impact statement” discussing the environmental effects. The production of these statements can be burdensome and costly. But when potentially irreversible losses are involved, and when officials cannot specify the magnitude or likelihood of such losses, the public, and those involved in making the ultimate decision, ought to know about them.
So too in the domain of public health. If a risk – of, for example, avian flu – is highly speculative, we might nonetheless take precautions in order to preserve flexibility for the future. The special concern about overuse of antibiotics, in increasing resistance, involves the same goal. And when officials undertake precautions against low-probability risks, an intuitive concern about irreversibility is often the animating concern.
Finally:
[T]he idea of irreversibility is not without ambiguity. Let us consider two possible interpretations. Under the first, an effect is irreversible when restoration to the status quo is impossible or at best extremely difficult, at least on a relevant timescale. For example, the “decision not to preserve a rich reservoir of bioiversity such as the 60 million-year-old Korup forest in Nigeria is irreversible. The alteration or destruction of a unique asset of this type has an awesome finality.”40 If this is the appropriate interpretation of irreversibility, then it is an aspect of seriousness. A second interpretation, standard in the economic literature on options, sees irreversibility in terms of sunk costs. The two interpretations lead to different understandings of the problem of irreversibility and the Irreversible Harm Precautionary Principle.
This paper is short, clear, and very helpful. Read it.
