A few weeks ago, scary links spread across social media to the effect that koalas are “functionally extinct” as a result of the recent catastrophic fires in Australia. Of course, reality is often more nuanced than Facebook posts, and “functionally extinct” is a technical phrase that doesn’t necessarily mean what it seems to.
So are koalas really just about extinct now?
The short answer is no, they’re not, although the species may indeed be in bad shape and climate change is largely to blame.
Koalas and Functional Extinction
The scary social media posts either referred to, or actually linked to an article in Forbes that quoted the Australian Koala Foundation as saying the species may be “functionally extinct,” and that 1000 koalas may have died in the fires and that 80% of the animal’s habitat may be gone. Since its initial publication, the article has been edited to sound less alarming and to reflect the fact that some experts think the situation with koalas might not be as bad. Several other publications have also issued articles on the subject (such as this, in the New York Times) that attempt to walk back the panic a bit and provide some additional context.
But what does “functional extinction” mean, and is it really correct to calm down about koalas?
What Does “Functional Extinction” Mean?
The original Forbes article defines “functional extinction” as meaning a population no longer plays a role in its ecosystem and is no longer viable. These are actually two, ecological irrelevancy and non-viability, very different situations, and while they can obviously occur together, they can also occur separately–and neither means that the species is “basically gone,” as in a hopeless situation or a foregone conclusion.
Properly speaking, “functional extinction” refers only to the first problem described in the Forbes article; that a species can no longer participate ecologically. In fact, a species can be functionally extinct even when its population is still big enough that its existence is not seriously threatened–instead, functional extinction means that other species in the same ecosystem react as though it is already gone and they die out.
A good example of functional extinction is the American chestnut*, which is by no means extinct, but which was devastated by an accidentally introduced disease some decades ago. Some trees proved resistant, and the root systems of young trees often survived and still send up shoots that sometimes manage to produce a few nuts before succumbing to the disease again. There are also well-organized efforts underway to breed blight-resistant American chestnuts, and I have in fact seen a blight-resistant seedling (it was given as a retirement gift to a noted naturalist at a party I attended). The species is likely to survive–but anything dependent on American chestnut forests is likely already gone.
Insects and birds and bears and whoever else once ate parts or products of this species must now do without.
So not only does “functionally extinct” not mean “almost extinct,” the concept is important precisely because it applies to species that may still be relatively abundant–and yet its decline is causing other extinctions around it.
Koalas themselves are not currently listed as “endangered,” or even “threatened,” only “vulnerable,” and although that assessment was conducted in 2014 and may now be outdated, it’s also possible it’s still accurate–the current status of koalas is apparently a matter of debate, since they are difficult to accurately count in the wild. But that doesn’t mean the species isn’t functionally extinct, nor does it mean that Australia is not in the process of losing something important.
What depends on koalas?
“Population” doesn’t necessarily mean “species.” Most species consist of multiple populations that interbreed with each other to greater or lesser degrees, and one population can become non-viable or even extinct and leave the rest of the species doing just fine–or, a species can go extinct one population at a time, or all at once if one population is all there is.
The study of population dynamics is a whole branch of conservation science and I’m not going to get into most of it here (I don’t know most of it!). The relevant point is you can have a species that still has living members but is almost certainly going to go extinct. In fact, the species could actually still look quite large and yet be non-viable. For example, passenger pigeons could only breed in very large colonies. The phrase “hunted to extinction” evokes images of heartless gun-toters searching out every last member of a dying species, but that’s not what happened to the pigeons. Instead, they were so ridiculously abundant that no one saw any reason not to harvest them freely, and then they were slightly less abundant, and then all of a sudden there just weren’t any more–because the still-huge flocks had dropped below the threshold necessary for the birds to breed. Another, perhaps more common, scenario is that habitat loss fragments a species into lots of little, genetically isolated populations, each of which is too small to sustain itself. The species might have tens of thousands of members, but if they are scattered across hundreds of tiny refuges able to breed only with their cousins, the situation is dire.
They are like a person falling from the top of a sky-scraper. In one sense, they are fine until they hit the ground, but in another sense they are obviously not.
Extinction can take a long time, especially in species where individuals are long-lived, and a few individuals can persist, unable to breed at replacement, for decades or more, and yet their loss is more or less assured. The concept of the non-viable population is another important one for conservationists to pay attention to, for it, too, points to a type of catastrophe-in-progress.
An yet “non-viable” doesn’t mean “doomed” or “hopeless.” Species have been pulled back from the brink before. Sometimes the falling man is rescued.
Are Koalas Functionally Extinct or Non-viable?
Are koalas functionally extinct? The Australian Koala Foundation says that they are, but it’s important to recognize that the group made the announcement in a press release (calling for political action to protect the species) back in May. So no, the fires probably haven’t pushed koalas to the brink–they were there already. As to what the fire has done to them, we really don’t know. It’s too soon for anyone to have done a real assessment.
The leader of the Foundation, Deborah Tabart, appears to conflate functional extinction with non-viability, but from her statements quoted in the New York Times (the same article I linked to earlier) it is clear she considers both to be true.
Both the Forbes article and the piece in the NYT make clear that some experts disagree with the Foundation’s assessment, apparently due to a perceived lack of data on the subject. I’m not in a position to weigh in either way–though I will say that “hey, there MIGHT be more koalas than you think, they’re hard to count!” is not really a comforting argument.
In any case, the Foundation has put the results of their assessment online for public review. Here is the link.
The real reason (again, based on the NYT piece) that Ms. Tabart’s assertions are controversial is not that she might be wrong but that she might be misunderstood, that people might think the koalas’ case is hopeless and stop fighting for them. Public perception is an important issue, but if koalas ARE either functionally extinct or non-viable as a species, then we do need to know so we can do something about it.
Koalas and Climate Change
That koalas are in trouble is not in any serious doubt, despite their not being officially listed as endangered. There are several reasons. First, millions were shot for their fur in the few decades before and after 1900. More recently, habitat loss has become the critical factor as more and more of Australia’s native eucalypt forests are cleared. More than 80% of their original habitat has been lost. And deforestation not only limits the total amount of space where the animals can live (and hence limits the total number who can live), but also fragments the survivors into increasingly isolated small populations. Living near human development also leaves the animals vulnerable to being hit by cars or attacked by dogs.
But koalas are also considered one of the world’s ten species most vulnerable to climate change; not only are they very specialized animals (specialists categorically handle environmental disruption badly), but Australia’s climate is among the fastest-changing in the world.
The clearest danger is from heatwaves and drought. One area lost a quarter of its koalas in one heatwave in 2009 alone. Drought and heat together stress the trees and reduces the moisture content of their leaves; koalas not only depend on eucalypt leaves for food, but also for moisture (though the animals will drink if water is available). Heat-induced water stress is the primary factor that will shrink koalas’ range in the coming decades. Some conservationists are arranging supplemental drinking stations for koalas and other wildlife, and the animals do use the stations, but it isn’t known yet whether the extra water will help with survival.
But then there is fire. Fire can kill koalas directly, and the animals can also starve to death in the time it takes a burned-over forest to green up again. Eucalypt forests do burn sometimes, and koalas evolved with fire, but several things are different now. First, the badly-fragmented nature of koala habitat means that now if an area loses its koalas due to fire, koalas from other places can’t come in and repopulate the forest as it grows back. But the other new thing is climate change; by allowing much larger, more devastating fires, it has increased the scale of destruction to where a single fire event could become an existential threat to an entire species–this year alone, Australia’s north coast has lost a third of its koala habitat. That’s not the only region that has burned, either. Where will the animals who survived those fires go? What will they eat until the forest grows back?
About Those Scary Posts….
It’s easy to get panicked seeing those social media posts, which seem to imply that this year’s fires have burned up so many koalas and so much of their habitat so as to suddenly doom them. The truth, as always in more nuanced, and panic does not help. But while a careful reading of the situation is always helpful, it is not necessarily very encouraging in this case.
Koalas are not doomed, and it is far from clear how bad their situation is, but it is clear it’s dire, not least because the threats to the species are complex and can’t be solved with a single stroke of a pen (as might be possible if hunting were still the primary threat).. We’re talking climate change, land use policy, economic development, human lifestyle issues, all of which depends on the principled cooperation of many, many people for any hope of progress. And if koalas are in danger, than so is everything else that depends on the same habitat and anything that depends on koalas.
And as of today, Australia continues to burn.
*The chestnut example and several other un-cited portions of this post are based on material I learned in grad school.