Source scarcity and sink scarcity

I learned this useful elementary distinction about sustainability from some more stuff Dad let me read in draft during a recent visit. Source scarcity refers to stuff like oil or potable water that might run out. Sink scarcity refers to the ecosystem’s capacity to absorb or dissipate waste without becoming catastrophically toxic.

Here’s how Herman E. Daly (pdf) puts it: “In the ecological economics vision the opportunity cost of encroachment is of two kinds: the emptying of environmental sources [depletion], and the filling up of environmental sinks [pollution]. The economic subsystem lives by a metabolic flow, an entropic throughput from and back to the environment. Low entropy resources are taken from the environment (depletion) and eventually are returned to the environment as high entropy wastes (pollution). Just as an animal lives from its environment by its metabolic flow, so the economy lives from the environment by its entropic throughput.”

In the previous post on global warming both sorts of scarcity featured. So on the source side Crazy Vaclav has rigorously calculated that if we converted every scrap of vegetation on Earth into biofuel it would replace one fourhundredth of our current civilization-sustaining fossil fuel consumption. (Once, and then we would starve.) Oops, so much for the saving graces of kudzu and grass clippings. On the sink side Crazy Vaclav notes that to sequester only 10% of global warming-inducing carbon dioxide flux would require the entire volume of annual oil extraction.

It turns out from this and other analyses (Dad’s working on water resources now) that we’re probably in more trouble from sink scarcity than source scarcity. That is, we’ll sooner ruin ourselves to death than run out of stuff to ruin ourselves with. Timescale seems to be in the low decades. I really don’t know quite what to do with disaster on this scale, so I just try to drive a little less.

Update: Because I think Dan might find this interesting I’m going to poke him by suggesting that this is an example of embeddedness. Daly has a nice venn diagram too, but his has the economy (and, by extension, society) embedded in the ecosystem.