Life span Archives | JuneauNature

Overlooked elders

The older I get, the more I think about the importance of mean and maximum species age. How does age of a community’s members relate to the other great conceptual underpinnings of Ecology 101: trophics, succession, landscape ecology, resilience and productivity? How does understanding of species longevity inform sustainable lifeways?

In the 3rd edition of The Nature of Southeast Alaska, I added a sidebar called Harvesting longevity, about often-overlooked antiquities. Here’s the first and last paragraph from that cross-taxon tour through mollusks, groundfish, trees, and deer:

Maximum recorded ages of Alaskan groundfishes. Our state’s oldest and second-oldest documented fish—a 205-year rougheye and a 157-year shortraker rockfish—both came from Southeast Alaska. Data from Munk (2001)

‘Whether studying clams, fish, deer or trees, northern researchers and naturalists frequently learn that life-span data from southern climes are inapplicable here. Underestimating longevity has serious consequences, especially for wild flora and fauna treated as commercial, sport, or subsistence species. . .

Compared to many large, hollow-centered yellow cedars farther south on the Tongass, Juneau’s cedars are relative youngsters. The extracted increment core suggested this 16-incher on south Douglas Island probably didn’t colonize until the late 1600s. Just a teenager in yellow-cedar years!

. . . ‘Harvest’—a term borrowed from agriculture—is of dubious merit when applied to seas or forests where cycles of birth-to-death are less visible, less understood, and less amenable to control. The consequence of overharvest is quickly obvious to a farmer, who sinks or swims financially on personally owned land. But when ‘harvesting’ wild ‘resources’ from public lands and waters, it’s harder to assign blame, or to instill restraint. For some managers and harvesters, exhaustion of one species is simply a cue to move on to another one, perhaps equally ill-suited to commercial or even casual extraction. This frontier mentality is a bull in the china shop of long-lived species.’

download sidebar essay Harvesting longevity (1MB)