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Australian mathematicians say some endangered species “not worth saving”

The views expressed are those of the author and are not necessarily those of Scientific American.


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Some endangered species on the brink of extinction might not be worth saving, according to a new algorithm developed by researchers at the University of Adelaide and James Cook University, both in Australia.

Dubbed the SAFE (species’ ability to forestall extinction) index, the formula takes current and minimum viable population sizes into account to determine if it is too costly to save a species from extinction. The research was published online March 30 in the journal Frontiers in Ecology and the Environment.

Co-author Corey Bradshaw, director of ecological modeling at the University of Adelaide’s Environment Institute, said in a prepared statement that the formula is “the best predictor yet of the vulnerability of mammal species to extinction.”

The study examined 95 mammal species, 20 percent of which are endangered and 10 of which are on what the authors call “the tipping point” where they could be at the “point of no return.” That tipping point, according to the authors, is a species with a population below 5,000 individuals.

Likening conservation choices to triage during wartime, Bradshaw told The Sydney Morning Herald, “During wartime, medicos have to go out and say, ‘Well this guy’s too far gone, we’re not going to waste our time because there’s too few of us.’ … We have to do the same thing in conservation, because we don’t have unlimited resources, money and things that we can buy back forests or restore completely degraded ecosystems.”

The authors say that conservationists could use the formula to redirect efforts toward species that are more likely to avoid extinction. “For example,” Bradshaw said in his statement, “our studies show that practitioners of conservation triage may want to prioritize resources on the Sumatran rhinoceros instead of the Javan rhinoceros. Both species are critically endangered, but the Sumatran rhino is more likely to be brought back from the brink of extinction based on its SAFE index.”

Other species that might not make the cut under the SAFE index include the northern hairy-nosed wombat and a flightless bird called the kakapo, which is intensely managed to prevent its extinction.

Interestingly, Bradshaw says that a species worthy of concentrated conservation efforts is the tiger, which he said “is at the ‘tipping point’ and could have reasonable chance of survival.” But with a wild population of 3,200 split among six subspecies, the tiger doesn’t quite fit his own algorithm.

The SAFE index uses information from the International Union for Conservation of Nature and Natural Resource’s Red List of Threatened Species before calculating a species’s chance of survival.

“I’d love to save everything,” Bradshaw told the Australian Broadcasting Company. “I just don’t think we can.”

Photo: The critically endangered kakapo (Strigops habroptila) by Brent Barrett via Flickr under Creative Commons License





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  1. 1. osmosium 3:28 pm 04/14/2011

    I’m wondering what the "algorithm" says about whether its worth saving mathematicians?

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  2. 2. jimaginator 5:21 pm 04/14/2011

    After the recent Japan earthquake/tsunami, I saw a scientist talking about the cost of building an unbreachable sea wall. He pointed out that although it would have been possible to build such a structure, is it right to do so, and NOT build hospitals, schools, etc.? At first, I found this quite cold hearted, especially as I watched whole villages disappearing, but on further reflection, it seemed like we MUST make such choices, like it or not. The same sadly would go for endangered species.

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  3. 3. Torbjörn Larsson, OM 5:30 pm 04/14/2011

    IIRC years ago there were results on how "key species" could help conservation efforts by allowing more sustainable public effort. Presumably one would have to reconcile such considerations (but it sounds like one could do it within the ROI model).

    @ osmosium: You loose that one; if the algorithm is useful mathematicians are worth it, if it isn’t it isn’t applicable to anyone.

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  4. 4. skapplin 5:36 pm 04/14/2011

    It’s about time we use some well-considered logic regarding the cost of saving species from extinction. Extinction is nature’s way of deciding what species are best suited for survival. By saving a species that is unable to survive without our intervention is subverting the natural process of evolution. It’s also potentially more expensive than it is worth when you consider where that time and money can be better spent.

    Without some sort of common sense we will eventually condemn our own species to extinction.

    I applaud the efforts of these researchers for taking the high ground. They are risking their careers on what will surely be an unpopular suggestion.

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  5. 5. renomargie 8:14 pm 04/14/2011

    Since the vast majority of the species going extinct are doing so due to human activity, we have a moral obligation to do all we can to ameliorate our impact. To do less is to be heartless. If it means we have to change what we do and how we live, so be it. If not, we will be the species in danger of extinction.

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  6. 6. blindboy 8:21 pm 04/14/2011

    "By saving a species that is unable to survive without our intervention is subverting the natural process of evolution."

    skapplin, virtually every species facing extinction is doing so as a consequence of "our intervention". Like it or not humans are influencing the evolution of a vast number of species.

    An understanding of ecology shows that this is a common process.Species influence the evolution of other species by interacting with them in all sorts of ways. The two things that make humans unique in this regard are the scale of our impacts and our supposed ability to consciously manage them. As to what is natural or otherwise you should consult a philosopher…..but only if you have a week to waste on linguistic circle games.

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  7. 7. jtdwyer 8:47 pm 04/14/2011

    This article states:
    "That tipping point, according to the authors, is a species with a population below 5,000 individuals."

    That statement seems to be contradicted by the linked ScienceDaily article, which quotes Corey Bradshaw:
    "The idea is fairly simple — it’s the distance a population is (in terms of abundance) from its minimum viable population size. While we provide a formula for working this out, it’s more than just a formula — we’ve shown that SAFE is the best predictor yet of the vulnerability of mammal species to extinction."

    Without seeing the research paper, it seems there is no consideration of resource investments necessary to save a species, assessment of alternative investment opportunities, or consideration for what population level can be considered sustainable for a specific species in a given habitat.

    Unless there is much more to this algorithm than meets the eye, this method does not seem to be useful.

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  8. 8. brock2118 10:48 pm 04/14/2011

    Species come. Species go. I suspect future generations will marvel at all the varied species of rats, goats and pigs found on isolated Pacific Islands in two thousand years. I think even the old growth forest of the Northwest will return in time, when viewed geologically its like trying to keep crabgrass out of the garden.

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  9. 9. jgrosay 2:49 pm 04/15/2011

    This is a good new, as not spending resources in unrecoverable endangered species can free money for other projects, for example treating diseases with a high QALY cost, the current upper limit seems stablished, no one knows by who or how in around 150,000 USD. Or not?

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  10. 10. pmontana 4:37 am 04/16/2011

    In a car crash with just two wounded people, you should first aid the one in worse conditions. In a train accident with hundreds of wounded people and few helpers, you should first aid those less dammaged AND PUT THEM TO HELP as soon as they can. I wonder if this criterion may be applied to endangered species.

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  11. 11. jmblock2 12:57 am 04/18/2011

    I would be curious to see that formula. I wonder if it looks anything close to the intro diffeq predator-prey relationships. I hope this better informs organizations on when to declare a group endangered. I think it might be a bit unfair to say tiger’s don’t fit his formula. 5,000 sounds like an expected value measurement and not some absolute. The tiger could be one of the extreme points where it can still survive while only having 3k left, but it just costs that much more. Definitely an important piece of work.

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  12. 12. graemeh 8:10 pm 04/18/2011

    If we are going to use this formula for our endangered species should we not then extend it to all areas of expenditure and base our budgets on return on investment. The huge cost to the world economy of supporting human populations in ecologically nonviable regions e.g. much of north west Africa- let them die. The cost of treating self inflicted injury and illness related to alcohol, tobacco, obesity – let them die. The huge cost of extending the lifespans of no longer financially contributing elderly – let them die. The questionable financial contribution made by economists – let them die.Its not as if we are are about to run out of people any time soon.

    When we base all our actions on financial return we have abandoned one of the few saving graces of humanity.

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  13. 13. geopelia 6:35 pm 04/20/2011

    New Zealand is trying to save the kakapo. Doesn’t that beautiful bird deserve a chance?

    The Black Robin was down to only one breeding female, "Old Blue", and was saved with great effort. Numbers are now increasing.

    The tuatara too is slowly increasing. It resembles a lizard, but has survived from the age of the dinosaurs.
    There is no other creature related to it, today.

    A new road was also changed to avoid disturbing a taniwha’s habitat!

    Link to this

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