“The most melodious wild music I have ever heard”
These were the words naturalist Joseph Banks wrote in his journal, his response to the exuberant rhapsody of birdsong filling the air as Captain Cook’s ship Endeavour dropped anchor in the paradise that was Discovery Bay in 1770.
If Banks and Cook were to make that same landing in 2017, they would hear – silence. Little did either realise that their own expedition, the first to map the coastline of New Zealand and study its wildlife, bears in large part the blame for today’s uncanny hush. For the Endeavour was carrying more than its crew. It also brought stowaways, in the shape of Rattus norvegicus, the brown rat. And it’s rats that have brought that music to a stop.
New Zealand’s native birds were/are endemic, ie. unique to that country, occurring nowhere else in the world. And, having no natural ground predators and therefore no need to take to the sky, they’d evolved over millennia flightless. So, easy pickings for the voracious invaders inadvertently brought to their shores.
Since that time, more than 70 species of birds native to NZ have been lost to the world, with more likely headed in the same direction, including the world’s heaviest parrot, the kakapo, and possibly the cheekiest, the alpine kea.
A shocking 26 million of the nation’s birds are killed by invasive predators every year.
Of course this is not a problem exclusive to New Zealand. The pattern is repeated all over. On Hawaii for example, the most isolated land mass in the world, native plants and animals evolved, as in New Zealand, without aggressively competitive or predatory species. The native species, not having had to compete themselves, are “more gentle than others, leaving them vulnerable to the ‘meaner’ species … being introduced to the islands.”
This is one of the ‘meanies’, who indiscriminately demolishes Hawaiian birds, insects, plants and flowers. He doesn’t belong there, but he sure has made himself at home.
Islands that once were regular Gardens of Eden where all lived in harmony, are today red in tooth and claw. And most often, the teeth and claws belong to Rattus norvegicus, or Rattus rattus, the black rat. Rats have found their way, courtesy of humans, on to more than 90% of the world’s archipelagoes, and embody everything that characterises an invasive species:
- Rapid reproduction
- Fast growth
- High dispersal ability
- Ability to live off a wide range of foods
- Ability to adapt to different environments
- Association with humans
Mammals like the rat are not native to oceanic islands, which are predominantly the domain of birds. Two-thirds of extinctions over the last 500 years have occurred on islands, largely at the paws of invasive mammals. Islands make up only 5.5% of the Earth’s land mass, but are home to 15% of all land species. They are hotspots of biodiversity. And that makes islands in particular, critically important for conservation.
So, how to stem the alarming losses in biodiversity?
Money for conservation is always at a premium. So much to be done, and never enough funding to do it. $21.5 billion is being spent annually, yet in places it’s hard to see much impact on biodiversity. It’s vital to direct funds to projects that will yield good results. And conservationists have found, especially on islands, the only effective method of stemming biodiversity loss is eradication of the invasive species that are pushing the natives to extinction. When the invaders are removed, the beneficial effect on native species is dramatic.
Different lands, different species demand different eradication methods. What works in one locale, fails in another. Our own ‘meanie’ here on the island of Britain is the American mink brought across the Atlantic to be farmed for its fur. Now escaped into the wild, these invaders have eaten their way through the water vole population, pushing the little rodents to the cliff edge of extinction. Mink are being trapped with the help of volunteers, and then shot in the head.
“It’s not something I get any satisfaction out of, but I am trained to do this, and we dispatch them as quickly and humanely as possible to cause minimal distress to the animal,” says river biologist Jamie Urquhart.
( I once saw a mink in the river at a National Trust property. I began an email to notify the Trust, but then couldn’t bear the thought of being responsible for the animal’s death, and deleted the email.)
In the Galapagos Islands, feral goats spread like wildfire, munching their way through forests and native fauna until nothing was left but bare grass. Native birds, invertebrates and the famous Galapagos tortoise were all endangered. Rangers hunted the goats down on land and by air, and shot them, 55,000 of them just on one island. The now goat-less islands reforested and recovered with gratifying rapidity.
In the Seychelles, where the invading Indian red-whiskered bulbul was ousting its native cousin, nets were used, and “rifles to get the last remaining few.”
In New Zealand, lethal traps and poisoned bait have been ‘successful’ on small islands, but as they are labour-intensive (requiring constant checking and resetting) they’re not practical over larger areas. Zero Invasive Predators (ZIP) is developing more effective ‘tools’, from “more attractive lures to electronically monitored traps.” The traps being used kill the rats instantly. “You don’t get those kills where it just breaks the back; we don’t want prolonged suffering,” says Aitken, one of the government-employed eradicators.
This is ZIP’s latest prototype: “Nailed to the tree a few feet off the ground is a shiny orange-and-black contraption called the GoodNature A24. Powered by a gas-fired piston, it delivers a quick, fatal blow to an animal’s head as it tries to snatch the bait inside. The device can kill 24 rats or stoats with a single canister of gas, requiring fewer of these strenuous, time-consuming trap line tromps, thereby saving on labor costs.”
Whatever method is used, eradication means no more nor less than the killing of every possible individual animal of the unwanted species in that territory. ” Most critics point to the ethics of the matter. Killing animals whether they are invasive or not is wrong, they argue, and uncompassionate. Killing wildlife for conservation seems counterintuitive. Isn’t conservation supposed to be about conserving wildlife?”
Some critics even see eradication as another manifestation of racism – prejudice against the non-native. “Certainly the Nazi drive to eliminate non-indigenous plants was related to the campaign to eliminate non-Aryan people.”
But an argument for eradication is that often, the native wildlife needing protection is found nowhere else on the planet, whereas the invaders such as the rats, are generally very widespread. Reading that sentence back and substituting the word ‘Aryans’ for ‘native wildlife’, and ‘Jews’ for ‘rats’, it does sound horribly like the Nazi justification for the Holocaust, doesn’t it? And labelling a group (Jews or rats) ‘vermin’, makes them so much easier to eliminate – it transforms eradication from a murderous crime into a public good.
Even if we accept that the uniqueness-of-the-endangered-native-wildlife argument makes sense at species level, does it justify killing thousands of sentient animals who are just getting on with their lives best they can?
Suppose eradication is a necessity, aren’t there non-lethal methods that could be used?
Yes, there are. Some are not always a practical option, some are just bizarre, and some pose unknown risks.
The obvious solution would be to trap the invaders and transport them back to where they came from. And on occasions this has been done. But imagine the politics, the logistics, and of course the cost involved of say, catching, keeping alive and shipping every veiled chameleon from Hawaii back to Yemen. And where on earth would you take the tens of thousands of feral goats from the Galapagos? Multiply that by thousands of conservation projects and it’s clear that can rarely be an answer.
Researchers in Australia have a novel approach. Remember the native species are invariably ‘gentler’ than the invading ‘meanies’ whose successful proliferation at the expense of the natives is down to their adaptability and aggressive competitiveness? Since there is little to no hope of ridding the whole of Australia of its mercilessly predatory feral cats, researchers there are trying to “force natural selection’s hand”.
They’ve placed hundreds of small endangered endemic marsupials in a pen with a couple of the cats. The hope is that the smartest marsupials will learn to survive, and pass on their cleverness genes to their offspring. But such human-contrived evolution of the marsupial could take 100 years or more. And if it seems like a big gamble, that’s because it is. No need for me to list possible objections, practical and ethical. They are all too obvious.
Genetic technology already available to us would be by far the most effective nonlethal tool for dealing with invasive species. Scientists have now found a way to not only alter the genes of a species – in this case a gene for producing male offspring only – but make that alteration inheritable. It’s called a “self-propagating gene drive system [which] promotes the inheritance of a particular genetic variant to increase its frequency in a population.” This would obviously require “fewer invasive organisms to be released in order to spread infertility and ultimately eliminate the pest population.” The animal basically would be programmed to (re)produce its own extinction.
New Zealand is one country taking a good hard look at this technology as a much easier, and definitely more humane way to rid the land of the invasive rats, mice, stoats and possums that are so destructive of its native wildlife. There is no question the gene technology would work. The invaders would die out, allowing the native species to flourish once more.
But, and it’s a big but, what it would also do, is create in effect a new species still retaining all the characteristics that made it such a successful invader in the first place. In other words, it would be impossible to contain these modified animals in the target location. Invasion is what they do best – they would spread far and wide with unknowable, and most likely catastrophic results.
The self-propagating gene drive is the perfect example of technology moving ahead at such a pace, it is way in advance of any ethical agreements surrounding its use. The international community needs to catch up fast, formulate, and sign up to a binding accord. New Zealand is by no mean the only country looking at the self-propagating gene drive as a conservation tool. And if something can be done, you can guarantee it will sooner or later.
To kill to save, or not?
“Not doing anything to prevent these extinctions is, in and of itself, an action—which is not compassionate to native species. We can sit there and watch animals go extinct, or we can do something about it,” says conservation biologist Holly Jones. “Killing things sucks. But when you realize the gravity of not acting, which in many cases equates to watching extinction happen in front of your eyes, I think there is no other choice,”
“We do have the ability to fix our damages. Which is why many conservationists believe we have an obligation to right the wrong when it comes to invasives since humans are, more often than not, solely responsible for introducing species into places they shouldn’t be.” Peter Haverson, another conservation biologist. “No other species has this capability, unfortunately.”
We’ve carried invasive species to every corner of the world, either deliberately – sheep, goats, dogs, cats and so on, then escaped and gone feral – or inadvertently, as with the rats. The cats, who are particularly pernicious predators of endangered wildlife, fall into both categories.
As we have caused the problem, should we be taking action to fix it? We can refrain from eradicating invasive species. That means standing by, letting individual endangered animals be killed by invaders, and allowing entire species to go extinct. Or, we can opt to kill the invaders – bearing in mind that rats, stoats and possums are people too. In conservation there is no fence to sit on. By not doing one, we are of necessity doing the other.
This is a cowardly cop out I know, but I’m so glad it’s not me having to make the decisions. What is your take on this most troubling of questions?
The most invasive species of all
We don’t just transport invaders around the globe. We ourselves are by far the worst invaders of the lot:
“From Africa, we’ve spread out onto every continent on Earth settling into jungles, plains, forests, deserts, mountains and more. All environments we touch experience extinctions and suffer from varying degrees of degradation. Many scientists even believe we are currently causing a mass extinction event of global wildlife, like the one that ultimately claimed the dinosaurs.”
“Believe”? The 6th mass extinction is no more a matter of belief than climate change. Strangely, I don’t hear anyone suggesting as a solution to the catastrophic loss of the planet’s precious biodiversity, the eradication of this, the most deadly of invasive species, Homo sapiens. Why is that?
Update 6th December 2017