Turns into cold logic
conservation planning’’, but it can be thought of as a type of triage for our dying biodiversity. It’s an idea that started in academia but has only in the last decade become a matter that drives government policy to decide where scarce conservation resources are allocated.
Tools like the algorithm, which use the cold logic of data to inform what are otherwise deeply emotional decisions, have become a dire reflection of the natural world’s health; given limited resources, which species deserve to be saved, even if that means others will be left to die?
Whether the priority list survives or not, it is a fascinating case study into how decisions are made around prioritisation, which will only become more relevant.
The ranked list, obtained under the Official Information Act, gives an insight into the trade-offs, and what we value most about our unique species.
The species ranked first is the Castle Hill buttercup, a tiny scree plant that evolved to exist in a very specific location, the broken limestone debris on the slopes of Castle Hill in Canterbury.
There are only 67 plants left, all within a 6ha reserve among the boulders that made the landscape famous. The reserve was the first ever set aside to protect a single plant. Dr Lance McCaskill, who led the effort to protect the buttercup in the 1950s, described its fate as an ‘‘age-long euthanasia’’, threatened by introduced weeds, grazing sheep and wild rabbits.
Two factors counted in the buttercup’s favour. It was named an iconic species, automatically putting it in the top 50; and it has a very high threat ranking at its genus level, Ranunculus.
(The algorithm took into account threat rankings at the order, family, genus and species level. Order is the broadest category of those – humans, for example, are one of hundreds within the primate order, one of eight within the Hominidae family, and the only species of Homo sapien.)
You could easily imagine an alternative weighting producing a different result.
Our most unique species, by far, is the tuatara. It is endemic at an order level – that means it has no living relatives, because they all died long ago.
The buttercup has relatives at order level, family level, and genus level – it’s unique only at species level, and even that is debated. It scores high because much of its genus is threatened, but it has plenty of more distant relatives.
If we prioritised uniqueness, we might not focus on the Castle Hill buttercup. We would defend the tuatara at all costs, because it has no parallel. But tuatara were ranked 29 because they have a stable population, and the fact they have no living relatives means their genus, family, and order are not threatened, because it’s the only one. Their uniqueness, in some ways, counts against them.
Another thing you could prioritise is representativeness – choosing a range of species across all kingdoms, recreating a pale imitation of the diversity that used to exist. That list would not include all five kiwi species, because they are closely related. It might not include takahe¯ , which are closely related to pukeko, which are safe. It certainly wouldn’t include 17 snails.
Could you imagine a politician unveiling a list of priority species that excluded kiwi or takahe¯ ? Would people care about conservation if the species people like the most could be excluded at the expense of a lichen or an earthworm?
Tomorrow: The other ways of choosing which species to save