I found myself asking a familiar question in an interview the other day: "How would you describe the differences between ecosystem functions, services, and values?" I find this to be kind of a Rorschach Test in some cases, but more frequently the answers tell me only that there's a lot of confusion out there about how these terms differ. These words sit in regulation and guidance appearing to be terms of art, but in practice they are applied liberally and fairly indiscriminately to situations in which there is something about the environment that we want to conserve.
I use the three together because they appear in a cluster so often, huddling together as if to generate strength in numbers. I mean, let's be serious: while there may be instances where they are formally defined (the Proposed Compensation Rule in 2006 defined all three), in common parlance you'd be hard-pressed to find a loosier or goosier set of terms. They gesture toward something we want to conserve, and help us to avoid the hard question of exactly what the substance of nature is that we desire to act upon. Look at any piece of environmental reg or legislation in the past 40 years, and you'll find that it's lousy with these terms: in the 1980 404(b)(1) guidelines "Functions" appears 83 times, "Services" appears 11 times (always paired with "functions and"), and "Values" appears 29 times (very often paired with "characteristics and").
My interviewer turned the question back on me, and I did the best I could. Here's my version.
VALUE: Although this is one of the least clear and most hotly debated terms in all of western philosophy going back 2500 years, I actually find this to be technically the easiest of the three. Value is simply that quality of an object that permits measurability and therefore comparability. We've been confused mainly because you can measure things (and therefore value things) in thousands of ways... we see the thousand ways but not the single character they all share: measurability. Price is a value, weight is a value, dissolved oxygen concentration is a value. Valuation is the use of a common measure to bring things into a frame of comparability. It is the genius of modern resource economics to have convinced everyone that price is a more fundamental value than others, and in the current social context there is some truth to the argument, but in truth there is no absolute measure of value. There is only the truth that two things may be compared, relative to each other or to a standard -- perhaps not objectively or numerically, but show me an object for which this is not true and I will show you something without value.
We sometimes experience a poignant dissonance when we attempt to compare things that have not been expressed in the same measure. It is often said that the value of a mountain or stream cannot be expressed in dollars -- that it is invaluable in some sense. This is certainly false -- what we have is a social disagreement on the measure of value to be used. When we say something is invaluable, what we really mean is that we disagree with the frame of measurement that is being imposed on an object. I would object to measuring my relationship to a friend in dollars, but I could agree to measure it in hours spent talking or in pickup basketball games played or in the qualitative strength of emotional connection. All measures are imperfect, but that shouldn't distract us from the commonality of the maneuver of measurement.
Debates among Adam Smith, David Ricardo, and Samuel Bailey in the early 1800s more or less laid the foundation for this understanding of the term, aided by commentary on these debates by Karl Marx about 40 years later.
FUNCTIONS and SERVICES: I tend to accept the argument that functions are physical processes, while services are the economic entities that are the outcomes of functions. Here we have a kind of territorial division between ecology and economics, with ecologists generally given deference on specifying functions, while services (being an economic term after all) are the realm of economists. But the policy realm of ecosystem services has thrown this all into a jumble. You find people talking about ecological functions AS services (e.g. pollination or carbon sequestration), with the result that the formerly-ecological territory is annexed to economics. This is the heart of the conceptual muddle. The more strictly-minded resource economists out there (Jim Boyd of RFF, for example) insist that a service can only be a final product -- pollination may be a function, but mature fruits are the service. This kind of distinction has a clear logical appeal, and is backed by a solid tradition in economics, but you don't see it respected in a lot of the ES world.
It's not only that economics crosses the epistemic boundary by characterizing functions as commodities. Ecologists also forget that a "service" is an inherently economic concept, and that if we're using the term service we have to live with the value regime of economics. That means that although biodiversity may have manifold ecological and biophysical measures, as service biodiversity is measured (valued) in price.
So in principle I don't think these are hard terms. But muddle arises in three ways:
1) Value is confused with acts of measurement: measurability is not measure, and just because something is measurable does not tell us what measure to use;
2) Functions are represented as commodities: this is equivalent to selling the actions involved transmission assembly instead of a car; and,
3) Services are represented as biophysical objects instead of commodities: just as Thoreau once said that "art is all of a boat but the wood", the service is only one measure of an object, and a fairly abstract one at that.
But as usual there's a lot of hay to be made by maintaining ambiguity about these terms -- that at least will not go away, no matter how many declarations are made about their final and true meaning.