The following is an extract from our nature newsletter Wild Wild Life. Sign up to receive it for free in your inbox every month.
There are many organisms teetering on the brink of extinction. Take the planet’s smallest marine mammals, vaquitas (Phocoena sinus), which are thought to now number fewer than 10 individuals in the Gulf of California, where they are constantly at risk from being caught in fishing nets. Or the last two remaining northern white rhinos (Ceratotherium simum cottoni) – both female – in Kenya. With no living males, odds of the species’ recovery look slim. Even if efforts to implant embryos made using sperm from now dead male rhinos or turn rhino skin cells into sperm cells are successful, any new rhinos that are born will face the twin threats of poaching and ever decreasing amounts of suitable habitat.
These are just two examples; the lists 44,000 species as being at risk of extinction, more than 28 per cent of the species that have been assessed.
Advertisement
We aren’t going to be able to save them all. Indeed, it is widely accepted that species slip out of existence every day, perhaps dozens of them, most unnoticed.
Should there be a point at which we just let go and accept that some species can die out, especially given that extinction is a natural process that happens through the course of evolution? And if so, how would we work out which species we could, with regret, wave goodbye to?
In the 1980s, ecologist Paul Ehrlich at Stanford University in California put forward the as a way to look at the risk of losing species. In it, he imagined an ecosystem as a plane flying through the air, held together by rivets, each one being a species. If one species goes extinct and a rivet pops out on a wheel cover, the plane can carry on flying. The aircraft can probably lose a few rivets like this and be pretty much unaffected. But if key rivets start to pop in the wings, the plane – the ecosystem – will crash.
If you follow this line of logic, then perhaps we can identify the most crucial species, concentrate our efforts on them and put less into saving others that might not make so much difference to the ecosystem as a whole.
To get a better understanding of the issues involved, I talked to at the Zoological Society of London’s Evolutionarily Distinct and Globally Endangered (EDGE) species programme, which was set up to identify the organisms we could least afford to lose.
“We needed ways to prioritise the very limited resources,” says Gumbs. “The idea was that we have these sets of species that might be critically endangered or endangered. How do we differentiate between them?”
Intuitively or implicitly for years before that, conservation had, and still does to a large extent, prioritised species that are charismatic, he says. These include big cats, primates and other animals that look cute and have forward-facing eyes. “So EDGE was designed as an objective measure,” says Gumbs.
EDGE’s approach is to seek out unique looks and behaviour. It aims to protect some of the most extraordinary and rare species on the planet – those with few close relatives on the Tree of Life. These are often underdog species that look or behave in unusual ways. If one of them dies out, we are losing a species that represents a whole evolutionary lineage that might not be represented anywhere else on Earth, says Gumbs. Examples include the (Nasikabatrachus sahyadrensis) found in India, which with its rounded, flattened body looks a little like a tiny, shiny elephant that has been squashed. Or the (Elusor macrurus), which can stay submerged for 72 hours by breathing through glands in its reproductive organs and often has a mohawk-like shock of green algae growing on its head.
Choosing to save species with no close relatives means you are safeguarding gene combinations not found in other organisms. Preservation of natural wonder aside, maintaining this broader amount of genetic diversity also ensures we preserve a wider array of the benefits that humans get from other species. Plants and the ecosystem services they provide are crucial to our lives, being useful for food, fuel, dyes, animal fodder, medicines and building materials. The we rely on for food, materials, medicines, and less compelling, as pets and display animals.
So, saving the strange and wonderful organisms has many benefits. But what about the other end of the spectrum? Are there less-special species we can afford to let go?
Although a few decades ago, you might have found some ecologists who backed that idea, none seem willing to voice that opinion now. Certain organisms are seen as keystone species, more crucial to the functioning of an ecosystem by keeping the numbers of other animals or plants in check, for example, and definitely worth trying to keep, but no one is keen on the idea of losing any species.
This is because of something called extinction debt. It might seem OK to lose a species here or there, because knock-on effects might not be seen immediately. But that is because there is a time lag between initial losses and the subsequent disappearance of more species. Grasslands might disappear and many species cling on, dwindling in numbers until, finally, years, decades or even centuries later, the debt is finally collected and the other species in the habitat also disappear.
For example, research published in 2022 looked at the reduction of forest cover caused by the second industrial revolution in the mid-19th century, and saw its .
Even when it comes to local species getting replaced by similar-seeming foreign invaders – such as British ladybirds (or ladybugs as my American colleagues call them) being outcompeted by invasive Asian harlequin ladybirds (Harmonia axyridis) – the potential loss worries ecologists. The harlequins might, like UK ladybirds, feed on aphids, but the invaders also feed on other ladybirds, scale insects and the larvae and eggs of butterflies and moths. It’s hard to be certain what effect the invasion is having on many of the local species, but if it does threaten them, it shouldn’t be taken lightly, says Gumbs.
“They have underlying different histories that brought them there, and they’re going to have slight differences in their physiologies and the way they live. When you start to look at long-term impacts, what might seem a quite similar species will probably end up being something very different,” he says. “If we learn another species went extinct, that could be another unknown benefit to people that we’ve just lost, that we don’t see on the surface.”
The bottom line is that even if some species might not seem as important or as cute or as special as a panda, a tiger or a turtle with a shock of green hair, we can ill afford to let any more of them die out. And as Gumbs says, “We are driving so many species extinct. I think it’s valiant that we make the effort to put things right where we’ve caused the problems, no matter how vain. It seems if we were to give up on the vaquita I would feel like, what’s the point in me going to work tomorrow?”
Gumbs’s passion makes me ask if we should even try to make tough choices on which organisms should live or die. Over evolutionary time periods, the arrival of new species has involved the natural extinction of others that were no longer as suited to a changing world, but it is hard to argue that the current level of extinction is natural. We did this. Some 44,000 species are on the brink because we have fundamentally altered the world by cutting down trees, eroding soil, damming rivers, burning fossil fuels, extracting water, polluting the environment and much more. The responsibility on us shouldn’t be to choose from what’s left, it is to right our wrongs and save as much as we possibly can.
