Bigger Picture
More birds than ever are at risk of being wiped out. At the same time, some of the most threatened species are pulling back from oblivion. What's going on?
More birds than ever are at risk of being wiped out. At the same time, some of the most threatened species are pulling back from oblivion. What’s going on?
HOW DO YOU MEASURE THE HEALTH OF THE planet? Is it the concentration of carbon-based gases in the atmosphere? Percentage of spaces left wild? Land protected from development? Amount of intact forest cover? Diversity of species in an area?
It’s all of those, of course, and more. But to me, the most emotional metric is how many species are at risk of extinction. And it’s a fraught measurement to make. You could count only the ones that are down to a pitiful handful of individuals. Perhaps you look at populations that are still numerous but declining fast. Or maybe you take into account how much their favoured habitat has shrunk, regardless of how many individuals are there. Or do you compare current numbers with what you estimate those numbers used to be? If so, what is the point of comparison — decades ago or millennia?
A study by the Canadian ecologist and evolutionary biologist Melanie Monroe and others published in Biology Letters at the end of last year takes a different tack altogether. They examined how more than 11,000 species of birds rose and fell through the categories of extinction risk in the International Union for Conservation of Nature’s Red List over nearly three decades, from 1988 to 2016. The Red List is the planet’s extinction bible. It has seven levels of extinction risk, ranging from species of least concern to those that are critically endangered, extinct in the wild and, finally, completely extinct. The latest Red List says roughly one in eight bird species is threatened with total extinction.
No matter what type of creature, the trend is for more to become more endangered over time, marching steadfastly through the Red List’s categories to the endgame. So, rather than assuming that species not in the direst categories will remain safe, Monroe’s team calculated the likelihood of a species becoming extinct based on past trends, no matter where it sits on the list now. Birdlife International, whose chief scientist Stuart Butchart is one of the study’s authors, calls this the build-up of “extinction debt.” The study refers to it as the “effective extinction rate.” And it’s rising.
“Our findings suggest that extinction risk in birds is accumulating much more than previously appreciated,” the study concludes, adding that it’s likely the same case for other types of creatures.
But here’s the more astonishing finding. Worldwide conservation efforts have cut the effective extinction rate by at least 40 per cent.
That means the frantic, often highly publicized, expensive sprints to save the last few individuals in a species — like Argentina’s hooded grebe, which breed only in fantastical nests built from water plants in lagoons in the plateaus of Patagonia, and global efforts to reintroduce the blue Spix’s macaw into the wild in Brazil — are succeeding in pulling some creatures back from the brink.
The problem, the study finds, is that the bigger the crisis, the bigger the response. Conservation efforts are focused on species of birds that are in the most danger and are therefore hardest to save. A safer, and less expensive, strategy would be to prevent species from making that ghastly march down the Red List’s categories. So, make sure the common species remain common, as Birdlife would say.
For example, the study in Biology Letters found that about a fifth of the birds it calculated will go extinct over the next 500 years are in the Red List category of least concern at the moment. It doesn’t say which of the winged beauties these will be; it can’t because this is all based on mathematical modelling, not on sifting through characteristics of individual birds. But the implication is sobering. It amounts to the realization that every species deserves protection, whether it seems to be endangered right now or not.
It would be easy to take heart from the study. It’s marvellous to think that human effort can keep a species, with all its evolutionary history, from vanishing from the book of life. At a time when it’s all too easy to see the dreadful effects of the human hand on the planet, some glimpses of success can make the spirit sing. I’ll take that.
But I have to note that the study also used the trajectory of the past three decades as the basis for calculating future extinction debt. The worrisome thing for me is that, thanks to ever higher carbon concentrations in the atmosphere and ever fewer trees in the Amazon (among other things), conditions on the planet are getting worse fast. It means that conditions for extinction are growing. Risk is rising. The task for us, then, is, tenderly and inexorably, to make it drop again.1