Jun 9, 2021

This project creaks to life…

I watched the wonderful Greta Thunberg documentary, Greta Thunberg: A Year to Change the World on one of our free-to-air streaming channels. In the first episode, she accompanies a glaciologist on a vigorous hike up to a glacier and, hearing of its steady retreat destined to become a rout to nonexistence, plaintively says: “I knew things were bad and I have read about these kind of things a lot, but to really be here and to stand on the glacier and to hear from you, who has so much experience about glaciers … it makes you realize it’s for real.” My heart pangs. I’ve been ignoring the local Extinction Rebellion bulletins, ignoring the brave handful of friends I worked with for a year.

A tweet by Corey Callaghan on a fresh look, by him and colleagues (via a paper here) at the global number of birds, allowing for many forms of data uncertainty, suggests 9,700 species and 50 billion birds. Call it six or seven birds for each human, which for some reason strikes me as low. The distribution of bird numbers in a species is, as the tweet shows, log-left skewered; Callaghan says, “Mother nature loves rare species.”

On the right of the distribution chart, four species have more than a billion birds each. Could I have guessed them? Probably: sparrow, starling, gull, swallow.

1,180 species, however, have less than 5,000 birds. I make a mental note to compare this numerical cutoff

He ends by saying their total estimate is in line with 1997 estimates by Tim Blackburn and Kevin Gaston.

IUCN’s three “threatened” categories range from Critically Endangered, i.e. more likely than not to go extinct soon; to Endangered: 20% chance of disappearing in two decades; to Vulnerable, literally vulnerable and not healthy as a population. Oversimplifying, these three categories equate to numbers of birds: Vulnerable means under 10,000, while Endangered means under 2,500 birds. Again oversimplifying, it seems Callaghan’s left-of-the-graph group of 1,180 small species fall between the the two “bad” IUCN categories and the less scary IUCN category of Vulnerable.

What will happen in the Anthropocene?