It’s not just extinction

I recently posted an interesting Atlantic piece arguing that, while we obviously have some serious problems, the evidence is just not there for us undergoing a true extinction event.  That said, very nice piece from Ed Yong that emphasizes looking at only extinction can be a misleading metric as to the threats to our environment:

Imagine if every animal and plant on the planet collapsed into a single population each, says ecologist Gerardo Ceballos. If lions disappeared except from one small corner of Kenya, the prey they keep in check would run amok everywhere else. If sparrows were no more except in one Dutch forest, the seeds that sparrows disperse would stay in place everywhere else. If honeybees became isolated to one American meadow, the flowers that they pollinate would fail to reproduce everywhere else. None of those species would be extinct per se, “but we’d still be in very bad shape,” says Ceballos.

He uses this thought experiment to show that fixating on the concept of extinction can lead scientists to overestimate the state of the planet’s health. Extinction obviously matters. If a species is completely wiped out, that’s an important and irreversible loss. But that flip from present to absent, extant to extinct, is just the endpoint of a long period of loss. Before a species disappears entirely, it first disappears locally. And each of those local extinctions—or extirpations—also matters.

“If jaguars become extinct in Mexico, it doesn’t matter if there are still jaguars in Brazil for the role that jaguars play in Mexican ecosystems,” says Ceballos. “Or we might able to keep California condors alive forever, but if there are just 10 or 12 individuals, they won’t be able to survive without human intervention. We’re missing the point when we focus just on species extinction.”  …

“The real trouble with mass extinctions, from a modern perspective, is that it’s really hard to know you’re in one before it’s too late,” says Jacquelyn Gill from the University of Maine. “By the time you compile the casualty list, the damage is done. What’s really powerful about [Ceballos’s new] study is that it focuses not on the losses, but on the early warning signals. Population declines are a common precursor to extinction, and it’s a process we can actually do something about.”

Alright, then, let’s do something about it.


About Steve Greene
Professor of Political Science at NC State

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