HOW DO we choose which of our species to save?

New Zealand has hundreds of endangered species. Some of them are birds, but there are also native fishes, beetles, ferns, lichens, bats, and shrubs at risk of extinction; even an endangered native leech.

The Department of Conservation simply doesn't have enough money to save every endangered species in New Zealand, so we'd better get used to the idea that some will be going extinct on our watch. How do we decide where conservation dollars go to minimise the number of extinctions?

Some species are popular enough with the public that corporate sponsors will chip in (and enhance their brand). Takahe, kakapo, kiwi, and blue duck together attract over a million dollars a year in private funding. Saving these charismatic "flagship species" supposedly has trickle-down benefits: rat control helps saddlebacks but also the beetles and spiders they share the forest with.


But the idea that flagship species have a kind of umbrella effect has been criticised by biologists recently. It's comforting to tell oneself that the species the public care most about are also the right ones to save, but is it true? A study just published in Proceedings of the Royal Society Series B, co-authored by Richard Maloney of DoC, tries to find out.

The authors start with New Zealand's 700 most-threatened species, and tackle two questions. First, how many extinctions would be prevented if we could take all the conservation funding - public and private - and use it most cost-effectively? Second, how many species could be saved if we stayed with the flagship-species model but carefully allocated budgets to maximise trickle-down benefits? The results were sobering.

The flagship species strategy turns out to be not too bad; when you save kiwi from extinction, a few other species come along for the ride. But the benefit is pretty small compared to what we would gain if we could allocate sponsorship money to species that need it most: this gets over twice the bang-for-the-buck.

Corporate sponsors, however, only want to fund pretty birds, not lizards or beetles, and especially not leeches. And sponsorship in New Zealand isn't even that generous; private finding covers on average 15 per cent of the annual budget for saving flagship birds like kakapo, or kiwi. In fact, sponsorship can even be detrimental: if it forces DoC to fund the bulk of a recovery scheme for a species that's not very high-priority, precious conservation dollars can be sucked away from species that need it more.

To make things more complicated, not all species are created equal. Some are much cheaper to save than others: an insect or frog species may only need a small patch of forest to call home, whereas a dolphin might need the entire western coast of the North Island.

And some species are just more special than others. The tuatara is the last living member of an entire branch of the reptile family tree, but the takahe is basically just a giant flightless pukeko; when picking what to save, tuatara get bonus points for being special.

This measure of evolutionary distinctiveness, called phylogenetic diversity, is another thing that has to be considered because we want to maximise not just the total number of species saved but also the total distinctiveness.

How can we save species more efficiently? No-strings-attached sponsors who let DoC work out which species are most in need; sponsoring whole ecosystems, learning to love beetles and lizards; and perhaps funding DoC adequately, so they're not forced to rely on private sponsorship.

-Dr Mike Dickison is Curator of Natural History at Whanganui Regional Museum