Going, going, gone: how do you decide which endangered species are worth saving?

My elder daughter recently adopted a Sumatran tiger. Not literally of course, but an Auckland Zoo package bought as a birthday present, with the tiger chosen above the seven other species on offer because - at least according to my daughter's claim - it was the most endangered one. In fact, the estimate for the number of Sumatran tigers left in the wild varies between four hundred and seven hundred individuals, so the lack of accuracy is only countered by the fact that both extremes are so low. With countless other species similarly close to the edge, if not worse off, a key question has arisen in recent years: are some species more worthy of conserving than others?

Presumably the choice on offer in the zoo's Adopt an Animal programme is intended to increase awareness of the plight of these particular animals. But can there be many people at least in the developed world who are not aware of some of the ever-increasing roster of endangered species? Indeed, there are now widespread claims that we may be living through a mass extinction event, the sixth known. Interestingly, it's only been in the last few years that some sort of quantitative definition of a mass extinction has gained popularity over the earlier, somewhat vague ‘one hundred to a thousand times the background rate' designation, with a rapid (at least on a geological timescale) 75% loss of species deemed the minimum number. However, this figure appears somewhat arbitrary, yet is quoted in various general readership articles as the number of species currently headed for extinction! Evolutionary biologist Richard Dawkins has much to say on the subject of fundamentally meaningless statistics: for example, how is 74% so much less worthy of the term ‘mass extinction' than a mere one per cent more? Granted, there may just be too many unknowns for a consensus in expert opinion, but deciding on a one per cent cut-off line for such an event is surely creating a label for its own sake, useful for lazy journalists but little else.

The International Union for Conservation of Nature (IUCN) Red List makes for depressing reading, with around 7000 species listed between the three worst categories: critically endangered; extinct in the wild; and species that have recently become totally extinct. Even worse, it appears to be out of date, if the example of the Yangtze River dolphin is anything to go by. It appears on the first of these lists, as opposed to the third, where most experts agree it should now sit. The fact that no single organisation seems to have enough resources to compile definitive current data doesn't help. After all, if you cannot identify the species most in need, how do governments and agencies decide which ones to save (and, unfortunately, which to doom to near-future extinction)?

The environmental movement of the past half century has long capitalised on photogenic ‘poster' species such as whales, apes and the giant panda, which add a wow factor that has had the side-effect of concentrating much of the funding on them. This has regrettably deprived many less aesthetic species of publicity, and probably in the case of some species such as the Yangtze River dolphin, their existence.

There are strong arguments both for and against the continuation of this policy, although things have recently got slightly better as regards recognition for non-figurehead species. Late last year the BBC television series Dara O Briain's Science Club made a foray into this area with the question - covered at the programme's usual break-neck speed -  are pandas worth all the money spent on them? Palaeontologist Richard Fortey and zoologist Lucy Cooke presented arguments seemingly against the high level of resources accorded the giant panda. Indeed, the latter emphasised the decline of one third of amphibian species worldwide. The time has finally come to appreciate that non-cute species deserve much greater attention than hitherto gained. To this end, the decidedly unpleasing looks of the deep-sea blobfish have recently seen it voted World's Ugliest Animal in a concerted effort to improve awareness of all the species that are least likely to appear on any fundraising poster.

So considering how many species, including plants and fungi, are currently endangered, is it worth spending millions of dollars each year to preserve, say, giant pandas? After all, aren't the latter just a wee bit useless? With a diet that is 99% bamboo and a seeming lack of reproductive drive, couldn't they be viewed as an over-specialised, evolutionary dead end, doomed regardless of loss of habitat and poaching? However, it isn't as simple as that. The popular description isn't completely accurate, with panda libido in captivity seemingly less than in the wild, although admittedly females are apparently only able to conceive for a few days each year. Even so, is it worthwhile to spend millions on captive breeding programmes (involving artificial insemination) for these cute creatures when the money could be split amongst many other species?

Awww, cute...but is it worth it?

One of the key arguments in favour of figurehead species is that the publicity gained is then disseminated to other species in the same habitat, such as by keeping those environments as free of development as possible.  Preservation of entire ecosystems is a major element to the notion that for purely selfish reasons we should maintain as much biodiversity as possible. This is in order to preserve unique genomes that may one day prove useful in agriculture or as pharmaceuticals. After all, only about 5% of plant species have so far been studied for their medicinal properties, whilst the DNA of many species remains almost entirely unexamined. A good case can be seen with the Pacific yew, a conifer in severe decline that proved to be the source of an important chemotherapy drug. In a similar vein, loss of one species may cause the rise of another that is rather less neutral from a human viewpoint, whether it is an agricultural pest or a dangerous predator such as the aggressive Humboldt squid, which has largely superseded over-fished sharks around the Mexican Pacific coast.

So even without invoking a moral argument, there are plenty of good reasons why preserving as many types of organisms as possible may be important to our future.  Whether this can be achieved most efficiently via publicity-raising poster species is more difficult to ascertain. There are claims that we should support evolutionary-distinct species or those with a definitively viable breeding/cultivatable population, but this is hampered by the lack of detailed information mentioned above. For example, several population bottlenecks in the history of cheetahs have reduced their genetic diversity to such an extent that even a relatively comfortable population size - at least compared to some endangered species - is no guarantee of future salvation. In other words, the minimum viable population for a species is probably unique for each.

In addition, there aren't complete lists of members in each ecosystem for even relatively large creatures: it was only last month that the Olinguito, a Central American omnivorous mammal new to science, was formally described. With this lack of definitive information, it's little wonder there is a multitude of problems concerning even knowing where to begin conservation measures. Of course, spending funds on this sort of research, which has no immediate benefit to endangered species, would presumably take crucial funding away from vital preservation measures in the here and now. But since the research hasn't been done many factors remain little more than guestimates, thus creating a vicious circle as to which species require the most support.

This doesn't of course mean that dedicated ecologists are likely to be swayed from their labours of love by any amount of hard data. Whether the enormous efforts to save those species with miniscule populations is worthwhile in the long run remains to be seen. New Zealand's flightless parrot the kakapo, with less than one hundred breeding individuals left, is a prominent example. There are now so few that almost every bird has been named; but would it have been better to try saving multiple species with more likelihood of long-term survival? It's difficult to attempt objectivity when you are fighting for the survival of creatures that have been anthropomorphised even to the minimum level of naming them. Then again, it's often been the devotion of small groups of committed conservationists that pioneered the techniques now widespread, including the methods for publicising the plight of endangered species.

So it doesn't look like there are any easy answers in what has to be, if it is to succeed, a rapidly developing field. After all, it's only been a century since we stopped wiping out species for fun in the name of sport. Unlike the Higgs Bosun, some of the subjects involved in this area - the species themselves - aren't going to be hanging around for solutions at some indeterminate point in the future. As Gandhi put succinctly: "Earth provides enough to satisfy every man's needs, but not every man's greed." The problem is knowing where to begin on the mammoth task of fixing a planet-wide ecosystem. All I can say is good luck, because like it or not, we're all participants in this one!

Birds, bugs and butterflies: attracting nature to your garden

For many years I've tried to attract wildlife to my garden; perhaps there's something extremely relaxing about watching other components of the biosphere go about their business. Even the closest I lived to the heart of London, a largely overgrown garden provided a haven for all sorts of creatures from tiny wrens via boisterous squirrels to the odd, slightly mangy fox. Although I've discussed the behavioural changes seemingly present in urban animals I thought it would be worth exploring the pros and cons of attracting various critters to your garden.

As a child our family supported winter visitors, usually with bread crusts for birds and cow's milk - for some unknown reason - for hedgehogs. I've since learnt that the latter is a very poor choice as hedgehog food, so where the idea came from I don't know. Mind you, much bacon rind is probably too salty for birds, so I wonder how many animals we killed with our kindness! If you want to feed hedgehogs, cat and dog food is apparently among the suitable alternatives. Not that these days we put anything out for the hedgehogs that occasionally appear in our garden, often disappearing behind the wood pile at night when I'm out at the telescope (and startling me with their sudden snuffling). The reason isn't due to being anti-hedgehog, but the food would most likely attract other, less welcome rodents such as rats and mice.

Interestingly, hedgehogs are amongst the survivors brought to New Zealand by acclimatisation societies in the Nineteenth Century, along with many European bird species that also congregate in our garden: sparrows, blackbirds, starlings, song thrushes and various finches. As a side note, it would be interesting to tabulate these against the many imported species that didn't survive their first year in the New Zealand wild, such as robins and emus; clearly, there's some unknown adaption criteria going on here.

One problem I frequently faced in the UK but don't any more is the seemingly inexhaustible ingenuity of squirrels in getting to the content of bird feeders, as described in the post above. However, possums imported from Australia fulfil a similar, if nocturnal role in New Zealand, and are a major pest for numerous reasons. Again, keeping bird food for only birds is a primary consideration. Not that birds don't show cunning when it comes to getting at food: I remember visiting the Zealandia eco-sanctuary near Wellington many years ago and seeing the kaka bush parrot feeding from mini bins opened via foot pedal - that's the parrot's foot, not a human one.

Back to now. So why attract wild animals to your garden? Usually it's a two-way gain - humans watch the antics for minimal expenditure and the fauna get food, shelter or even a bath. It offers children a close up view of nature and the realisation that you don't have to go to zoos and wildlife parks for the experience: nature is all around us. It also introduces them to the diversity of the local biosphere as opposed to just the typical, ‘grand' fauna such as African savannah species or large sharks and rays that are kept in zoos and aquaria. To this end, the UK's Royal Society for the Protection of Birds (RSPB) organised the Big Wild Sleepout last weekend, the idea being to camp in your own garden or at an organised event in order to hear and possibly even see the nocturnal creatures we don't usually come into contact with. I only tend to be outside at night if I'm at the telescope, and must confess to frequently hearing the unmistakeable cry of the morepork, New Zealand's only native owl, but have yet to see one.

Talking of owls, birds are the obvious favourite to attract to your property, since it's easy for them to get around and escape from predators such as domestic cats. According to the RSPB over half of UK adults have fed garden birds. In recent years organisations have started to take advantage of all this previously unrecorded observational data by encouraging the public to submit sighting reports for collation. These projects range from observing familiar creatures such as butterflies and ladybirds, to tracking the growth of invasive species such as New Zealand stick insects in the UK's South West. The RSPB, which is a veteran of collecting such data, utilised a weekend in January this year for their Big Garden Birdwatch, the world's largest wildlife survey.

Following the State of Nature report released in May this year, it sounds like this sort of project hasn't come a moment too soon. The new assessment was compiled by twenty-five British wildlife organisations including the RSPB and makes for a sobering conclusion. It found that 60% of the 3,148 UK species under assessment have declined over the last half century, with slightly over 10% deemed under threat of extinction in the UK. It's impossible to know if the situation is similar in other nations, but such worrying statistics suggest that any help given by the public to aid biodiversity can only be for the better. But as per the hedgehogs and milk example, what other pitfalls are there to befriending fauna?

It is fairly widely known that common foodstuffs such as salted peanuts and desiccated coconut should not be given to birds, but how many people remember to soak white bread before putting it out so that it doesn't swell inside the animals' stomachs? Although you can buy purpose-made bird seed mixtures it is cheaper - and frequently better - if possible to grow a bird-friendly garden yourself. It depends on what species live locally, but some birds like open lawn for insect feeding, others prefer overgrown areas (the goldfinches in my garden are very keen on the latter) whilst other species prefer fruit or nectar direct from the tree or bush.

It isn't just birds either: as a child I remember a buddleia bush that attracted at least four species of butterfly whilst here in New Zealand a swan plant (a type of milkweed) plays host to dozens of monarch butterfly caterpillars over the summer. In addition, praying mantises lay their egg sacks on just about any vertical surface in our garden, masonry or timber, so spring sees a profusion of baby mantises heading for undergrowth. The trick is to keep them away from the swan plant; otherwise the caterpillars tend to disappear in their early stages at the expense of the mantises...

In contrast to planting your own, commercial ready-made food mixtures may have large carbon footprints or be grown in developing nations that could better use the land and effort for growing their own food. In addition, messy eaters will cause seeds to drop onto the ground where sterilised seeds can choke native growth and the non-sterilised ones germinate: we once even had a hemp plant that grew several metres in a month or so from some spilt seed!

Therefore having plants or garden layouts that provide food for birds can be as good as leaving out scraps or purpose-bought food. I suppose the main difference with the latter two is that you can place them where you like for ease of viewing. After all, watching birds eat is the primary attraction. Although you can buy bird feeders I prefer to make my own, with a variety of success rates depending on the design. The most popular to date has proved to be table hung from a cherry tree, with half apples spiked on nails attracting a regular stream of silvereyes. Here in New Zealand you can even feed nectar eaters such as tuis via an old wine bottle containing sugar solution.

One important issue is when you should feed wildlife. The best time of year is obviously winter, when natural foodstuffs are least available. As a general rule, it's probably best to stop feeding once chicks arrive, so that both they and their parents don't start relying on human support. However, in addition to providing food you can also create habitats suitable for assorted wildlife from mammals to invertebrates. As a boy I made a nesting box for a Cub Scout badge, but it was never inhabited, probably being located in too low and too busy a position for birds to consider safe. Today you can buy all sorts of homes and feeders suitable for different species and climates so there's no shortage of easy options. The RSPB recently started supplying a free guide to building animal homes in your garden, ranging from bird box to hedgehog shelter. I can even claim success with my homemade weta motel (current resident: one female tree weta), although it took some time to gain any inhabitants other than numerous, small cockroaches. Note the weta legs poking out of the hole below!

Most of these are generally great aids to wildlife and observing wildlife, although I find the idea of building small ponds not particularly attractive since any standing water in my gardens usually attracts biting insects to lay their eggs in it. When I lived in East London any empty plant pot that collected rainwater swarmed with wriggling mosquito larvae in next to no time. Not nice!

The one thing about this sort of amateur interaction with biology is that you can do as much or little as you like as quickly or slowly as you like, but you are bound to get some form of success. Having said that, there are still plenty of species I'd like to spot in my garden. I have a large pile of volcanic stone that would look good in a far corner of the back garden as a potential lizard home; friends down the road are lucky enough to have skinks and geckos around their grounds. I'm also ever hopeful of various sections of rotting timber serving as home to peripatus -  a.k.a. velvet worm - an ancient form of life that lies somewhere between worms and arthropods. Although I've definitely seen some small white things that might just possibly be very young ones...