Comment to: Faith, D. 2018. Biodiversity’s option value: A comment on Maier (2018). Ambio. https://doi.org/10.1007/s13280-018-1069-0.


In a recent essay (Maier 2018), I present a closely argued case for why option value, as Dan Faith has understood it for a quarter century, is not a credible basis for conserving biodiversity. Unfortunately, Faith’s comments (2018) on that essay are not substantively relevant to it and purport to defend his views by contradicting and abandoning them.

One line of Faith’s (2018) discussion concerns “historical perspective.” This, according to him, consists in past expressions of concern about biodiversity—for example, a 1974 report that a symposium’s participants expressed concern about narrowing future choices, and Pope Francis’ expressed concern about depriving future persons of resources. But the fact that some persons expressed concern has no substantive relevance to my essay’s reasons for why option value is a non-starter as a basis for that concern. Additionally, expressions of concern are not, in themselves, normatively important reasons or reasons to think that the object of concern is worthy of concern—no matter what that object is. Slaveholders expressed concern about freeing their slaves and consequent narrowing of choices for producing crops. But that is not a morally important reason for why slavery ought to have been “conserved.”

Elsewhere in his comment, Faith emphatically denies that the “core idea” of biodiversity’s option value is the doubtful idea that biological variety has either some definite or possible expected benefit realized in the future, while insisting that it is some verifiable current benefit/good that people enjoy. This characterization of option value is novel. It is also misleading because “option value” is otherwise universally understood as referring to benefits that might be enjoyed by future persons or by our future selves. Currently enjoyed benefits are already extensively discussed by the econometrically inclined in terms of natural capital and provision of ecosystem services.

This novel characterization also contradicts and abandons views about option value that Faith has expressed for decades. That includes Faith (2017), which Faith (2018) complains I neglect. It states [all italics added]:

… the core value of biodiversity-as-variety… is a form of “option value”, capturing the value that variation has in potentially providing unanticipated benefits for humans in the future.

Option value refers not only to the unknown future benefits from known units of biodiversity, but also to the unknown benefits from unknown units.

… we must conserve more than [currently useful] units [of biodiversity], because other units may provide unanticipated benefits in the future.

This long-held idea of option value—as unanticipated benefits enjoyed in the future—cannot be coherently defended by means of re-defining it as some current benefit.

Faith (2018) also states that conserving biodiversity is the right thing to do. That may be true. But the possible rightness of conserving biodiversity is not relevant to my essay’s argument that option value (in Faith’s previous, long-held sense) offers no support for supposing that it is right.

Faith’s final remarks refer to an IPBES Assessment, publicly unavailable at this writing. A draft version of that document includes references to Faith’s earlier work that Faith (as an IPBES Assessment author) himself inserted. This does nothing to defend option value as a conservation rationale. Nor would option value’s plausibility as a conservation rationale be boosted if Díaz et al. (2018) had actually employed the phrase “maintenance of options” that Faith (2018) mistakenly attributes to them.