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Facing Extinction II: Making hard decisions

Facing Extinction II: Making hard decisions

Sacramento perch is an example of ‘gray’ extinction because it has been extirpated from its native habitats in the Central Valley. It exists only in a diminishing number of places where it has been transplanted. Photo is by Chris Miller of the Contra Costa Vector Control Agency and is from the CalFish website.

by Jason Baumsteiger and Peter Moyle

In part I of our blog, we projected a bleak future for many freshwater fishes, especially in California. Some difficult decisions will need to be made to prevent extinctions or to verify them.  However these decisions will rely on answers to one sweeping question: When is a species, in fact, extinct?

Some may argue this is a simple black/white or presence/absence question. But is it really? What if the species’ existence depends completely on humans? What if it no longer exists in its natural habitat or in the wild? What if it has been hybridized or genetically engineered? In such cases, is it fair to say this species is still the same as its wild predecessor?

In our recent paper, we attempted to tackle these questions and provide an honest, although imperfect, way to assess extinction. The first involves accepting that “grey extinction” exists. This is an area between formal threatened/endangered status and global extinction, where a species is in limbo – it is partially extinct. We know this sounds weird because under traditional usage extinction is an all or nothing proposition. However, there are in fact grey areas; they fall into five categories. Each represents ways a species may be partially extinct. These categories are by no means exhaustive, but do represent a reasonable framework where partial extinction can be examined closely. We look at these categories through the eyes of biologists trying to conserve species through either a single-species or a multi-species approach. We then weave these ideas into a decision tree to help managers recognize fishes (or any organism for that manner) which have reached “grey extinction” limbo.

Categorizing “grey extinction”

Mitigated extinction- This category represents the many ways that a species can become dependent on humans for its existence. The formal term is conservation-reliant but it just means that if we are not there to provide support, the species will quickly become globally extinct. Actions might include protection from predators, protection of habitat or even finding mating partners. Winter-run Chinook are a good example: they depend on humans for spawning habitat and early life-history protection (food, predator and disease avoidance). Without human intervention, winter-run Chinook (thanks to Shasta Dam) would quickly cease to exist.

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