How do we decide which species to save? (Image: Richard Wilkinson)
With more than 4000 species on the brink of extinction and limited resources to help them, conservation needs to move beyond the cuteness factor
“ALL animals are equal, but some animals are more equal than others.” The famously sanctimonious maxim from George Orwell’s Animal Farm captures the current state of affairs in nature conservation quite well. Though conservationists are uncomfortable admitting that we might have to let some species go extinct, they also know that it is impractical to try to distribute their efforts evenly.
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This makes prioritising inevitable. Every organisation involved in conservation does it, and they often focus on the same species – the cute and the colourful, the ones we feel emotionally drawn to. As a result, most mammal conservation projects target “charismatic” flagship species, leaving three-quarters of endangered mammals unprotected. Birds suffer a similar bias and other life forms rarely appear on the radar at all. But even if we become less emotive in our choices, deciding what to save isn’t just about biology – it is political and economic, too. If we want to allocate conservation time and money more effectively, we have some hard choices to make.
Even identifying the species in most trouble isn’t straightforward. In the past, they were more likely to be the high-profile animals that still get a lot of attention today. When hunting was one of the main threats of extinction, the species at greatest risk tended to cluster together on the tree of life – carnivores clad in fashionable fur coats or large, tasty herbivores, some with attractive horns or tusks. As global warming takes over as a main driver of extinction, however, this pattern is changing. “Smaller animals may be more vulnerable to climate change than they were to hunting,” says Jonathan Davies at McGill University in Montreal, Canada. “And once ecosystems start to collapse, extinctions may appear at random – a classic signal of mass extinctions.”
Today, the International Union for Conservation of Nature’s (IUCN) Red List provides an inventory of the extinction risk faced by as many species as possible. But with 4000 listed as “critically endangered”, just one step from “extinct in the wild”, it still leaves the aspiring conservationist spoilt for choice.
One solution might be to focus on areas that harbour the largest number of species – so-called hotspots of biodiversity. However, this can be surprisingly contentious. For a start, it isn’t always clear what counts as a species. Where a single species has recently and rapidly diversified into a large group of closely related species, these may not be valued as highly as more distinct species. Likewise, when scientists successfully argue that their favourite species should be split into two or more, some conservationists view this as taxonomic inflation and don’t consider the resulting species or subspecies to be as important as long-established ones.
Then there is the problem of judging which hotspots most need protection. It isn’t as simple as measuring overall reductions in biodiversity. Although biodiversity is decreasing globally, Maria Dornelas and Anne Magurran at the University of St Andrews, UK, found that . But rising biodiversity isn’t necessarily a sign that an area is thriving: it may be due to colonisation by alien species that do well in rapidly changing or human-made environments.
Maybe, instead of counting species, we should be looking at the larger branches of the tree of life and trying to preserve regions with high evolutionary diversity. In the early 1990s, Dan Faith of the Australian Museum in Sydney devised a way to measure such diversity using phylogenetic trees, a sort of evolutionary family tree where the length of the branches represents the years of evolutionary history separating the species. “It occurred to me that if you were to take such a tree and add up the lengths of the branches connecting all the species in a region, that would give an idea of what I decided to call its ‘phylogenetic diversity’ – the longer the distance, the higher the diversity,” says Faith.
Biological heritage
Together with Félix Forest of the Royal Botanical Gardens, Kew in London, . “We were able to show that areas with high phylogenetic diversity scores may not necessarily contain the most species, but they tend to contain the greatest variety of useful features, such as edible parts, medicinal properties, construction materials and so forth,” says Forest.
What’s more, phylogenetic diversity could boost conservation by creating a source of national pride. “The government in Australia is quite interested in this measure,” says Faith, noting that, with its unusual marsupials and monotremes, the country scores high on phylogenetic diversity. “They would like to add a biological dimension to the notion of what is heritage, so that we might strive to protect not just our cultural heritage, but our evolutionary heritage as well.”
While Faith’s approach allows conservationists to compare the evolutionary history contained in entire ecosystems, it doesn’t tell us about the evolutionary distinctness of individual species, which are still the main focus of many conservation efforts. That’s where the Zoological Society of London (ZSL) comes in. Its researchers have been busy calculating species’ so-called EDGE (Evolutionarily Distinct and Globally Endangered) scores. They first divide the length of each branch of a phylogenetic tree by the number of species at its tip. Then, to assess how evolutionarily distinct (ED) any given species is, they simply add up these values starting at the root of the tree (the ancestral lineage) and ending at the tip where the organism is to be found.
The ED will be highest for those species with a long evolutionary history and few relatives. “This gives you a measure of each species’ individual contribution to the phylogenetic diversity of a region, expressed in millions of years of evolutionary history,” says Sam Turvey at ZSL. ED is then multiplied with a factor reflecting how globally endangered (GE) it is, based on its Red List status. “The resulting EDGE score allows us to rank animals by phylogenetic uniqueness as well as extinction risk.”
The approach has generated top-100 lists of mammals, amphibians, corals and, most recently, birds, “on the EDGE of existence”, as the puts it (see diagram). “That’s not an exaggeration,” says Turvey. “As soon as we launched in 2007, we found ourselves in the very unfortunate position of having to declare the Yangtze river dolphin – the number one species on our list – to be extinct.” Intriguingly, some of the usual suspects targeted for conservation are well outside EDGE’s mammal top 100, including the tiger (“plenty of other big cat species”) and the African elephant (“not as highly threatened as it was previously thought to be”). “I would never want any resources to be stepped down from existing conservation projects, if these species still need them,” says Turvey. “But we’d like to highlight that there are many other species that also need conservation.”
“We now have top-100 lists for mammals, birds, and amphibians on the edge of existence”
Whether EDGE chart-toppers represent a good conservation investment is another matter. Some species, including Attenborough’s long-beaked echidna and the New Caledonian owlet-nightjar, haven’t been spotted alive for decades. Might efforts to conserve such species simply be wasting money on evolutionary losers? “That’s a good point, but you have to be really careful there,” says Walter Jetz at Yale University, one of the architects of the bird list. “I wouldn’t dare to call a bird like the shoebill – number 37 – a loser. Yes, it is the only bird in its family, but thanks to its unusual bill, it’s perfectly adapted for cracking certain types of snails, and may therefore play a crucial role in its current ecosystem and, who knows, others in the future.” He believes that if it weren’t for human impact, the shoebill might well be thriving. “And if we lose it, we’ll have to wait at least another 50 million years for such a bird to appear again – if it ever does.”
But Faith does worry that by focusing our efforts on the most unusual creatures we risk losing sight of whole branches of biodiversity that might more easily be saved. “I guess it would pay off to consider multiple scenarios and opt for one that doesn’t just maximise the outcome if everything goes according to plan, but also decreases the chance of losing a lot of species if it doesn’t,” he says.
“Obviously, when making decisions about how to spend resources, we should always try to get the biggest bang for our buck,” says Turvey, “and it is unfortunately true that we don’t have enough money or manpower to start protecting all species we’d like to save today.” But he cautions against assuming that a species is beyond recovery, because we know so little about the current status or abundance of many on the EDGE lists. Instead of writing species off, he argues, conservationists should be trying to raise more funds from more sources (see “Who holds the purse strings?“). “I think this persistent idea that the amount of conservation resources is fixed is fundamentally flawed,” Turvey says.
A more scientific approach to conservation could help rectify that. locating the 131 most evolutionarily distinct bird species of the 575 listed as “endangered” or worse by the IUCN to pinpoint places that deserve greater conservation attention. “Interestingly,” he says, “the countries that rise to the top are not the ones harbouring the largest number of bird species – that would be Colombia, Peru and Brazil – but places like Indonesia and Madagascar, as well as many smaller islands and mountain ranges, with many unusual and highly threatened species.”
Jetz hopes his map will empower these often resource-constrained countries when applying for conservation funding from international organisations such as the World Bank. “It might also generate funds from another source,” he adds. “If we could get the birdwatching community to appreciate that seeing yet another white-eye just to add one more species to your list may not be quite the same thing as seeing one of these highly evolutionarily distinct birds, that would be a great way to bring in ecotourism funds to support their protection.” Jetz’s map is online at , a project that brings together information on biodiversity and distributions. The hope is that its attractive design will motivate birdwatchers to share their sightings, providing information to boost conservation.
Beyond the charismatic
With resources such as the EDGE lists and Map of Life freely available, conservationists increasingly have what they need to make more objective decisions and monitor their efforts. So far, the EDGE programme has supported training for some 40 conservation leaders in 25 countries working to protect idiosyncratic species populating its lists, from the pygmy three-toed sloth to the giant salamander. Meanwhile, the IUCN is considering how to take phylogenetic diversity into account when selecting key biodiversity areas on which to target its conservation efforts.
“I think phylogenetic approaches will become ever easier to use, and thus more popular,” says Forest. “Technological and conceptual advances make it faster and cheaper to gather large amounts of molecular information from organisms. This allows phylogenetic diversity to be calculated for an expanding range of taxonomic groups and regions.” Such expansion should be good news for endangered species that don’t qualify as charismatic. Forest and colleagues are currently putting the finishing touches on an EDGE list for gymnosperms, a group of plants that includes conifers, cycads and ginkgos. “I’m curious whether the list will generate a similar amount of excitement as the EDGE lists for animals,” he says. “There are some pretty weird and rare gymnosperms out there, and they are fascinating, if you ask me.”
Perhaps one day there will be EDGE scores for all life – invertebrates, plants, even microbes. “That would be interesting,” says Faith. It would also expose the fact that emotional considerations will always play a part in our choices. “I don’t think anybody would seriously consider giving up on a mammal to conserve a larger amount of phylogenetic diversity in beetles or bacteria,” he says.
As for the human EDGE score, that is rather humbling. “In terms of evolutionary distinctiveness, we don’t even make the top 1000,” says Turvey. And when it comes to conservation risk, we are in the “least concern” category, which drops us even further down the list. “Of course we are a serious concern for conservation – but in a rather different way.”
See nine species high on the EDGE lists: “EDGE is the new endangered: The top species to save“
Who holds the purse strings?
conservation budget in 2005 was around £12.7 billion, according to recent research, equating to some £15 billion in 2014. The lion’s share of this – approximately 90 per cent – comes from domestic sources, including governments and self-funding by conservation areas, such as national park entrance fees. There is large variation between countries, however, with governments in low-income countries funding only 13 per cent of their own total conservation spending on average, rising to 97 per cent in the wealthiest countries.
A further 5 per cent of the global spend comes from aid organisations, including the Global Environmental Facility, which funds 22 per cent of this portion, the World Bank (19 per cent) and country-to-country donors, such as the US (7.5 per cent) and Germany (5 per cent). The hardest sector to quantify is private philanthropy and NGOs including Birdlife International, The Nature Conservancy, WWF, and the International Union for Conservation of Nature.
As well as looking at sources of conservation funding, the countries with greatest underfunding were identified, by considering the size of the areas requiring protection and the costs involved in conserving them. Top of the list were Chile, Malaysia, the Solomon Islands and Venezuela.
This article appeared in print under the headline “Ditch the panda”
