The Best Australian Science Writing 2015 (19 page)

It's all in your mind: The feeling of ‘wetness' is an illusion

Why aren't we dead yet?

The mind of Michio Kaku

Small mammals vanish in northern Australia

Dyani Lewis

Just after dawn, Danielle Stokeld sets out on foot to inspect small mammal traps nestled among spindly eucalyptuses and pandanus pines in Kakadu National Park in Australia's far north. In spite of knee-high spear grass, the ecologist with the Northern Territory's Department of Land Resource Management zips through her 2.4 kilometre route, managing to check all 117 traps in less than an hour. The reason for her alacrity: every last trap is empty.

Back at Kakadu's South Alligator ranger station later on that cool July morning, other researchers say they have fared no better. After two weeks of trapping, the dire reality is becoming clear. From 4000 traps at six sites, all the researchers were able to snare were a single delicate mouse and two northern quolls – spotted hedgehog-sized marsupials with long, fleshy tails.

In northern Australia, mammal populations are in free fall. Over the past two decades, scientists have documented sharp declines in quolls, bandicoots, and other native fauna. The plight of these animals has grown so desperate that in July 2014, the Australian government appointed the nation's first threatened
species commissioner, Gregory Andrews, a Department of the Environment staffer now tasked with devising broad approaches to stem the tide of extinctions. The solutions are not obvious, but mounting evidence points to the arch villain: feral cats, aided and abetted by fire.

The European influx beginning two centuries ago turned the island continent into a crucible of extinction. Since then, 29 land animal species have gone extinct, including, most famously, the thylacine, or Tasmanian tiger, which winked out early last century. Other vanished fauna include species of bettongs, bandicoots, potoroos, bilbies, and wallabies. Australia's losses represent about a third of the world's mammal extinctions over the past 500 years. Many disappeared before 1950, after getting squeezed out of habitats and falling prey to invaders including cats and European red foxes. Another invader, the cane toad, has been a bane to northern quolls, which eat the toads and succumb to poison they secrete.

Other species are barely hanging on: some 55 endemic land mammals – 20 per cent of Australia's total – are threatened with extinction. ‘You look at the outback and see how vast and natural it seems to be,' says John Woinarski, a conservation biologist at Charles Darwin University (CDU), Casuarina. ‘But we've clearly fractured its ecological processes.'

As losses accumulated in southern and central Australia, the sparsely populated north appeared to offer a safe haven. Bigger than Alaska, the tropical savannas that span parts of Western Australia, the Northern Territory, and Queensland have vast tracts of intact vegetation and, importantly, have proven inhospitable to the red fox. But the sanctuary was illusory. In the late 1980s, when Woinarski began his studies in the Northern Territory, 200 traps would catch 30 or 40 animals overnight. Nowadays, a typical haul is zero. ‘It's heartbreaking,' he says. ‘Things that were there a decade before have just disappeared.'

Feral cats are undeniably the chief culprit. In a paper published online in September 2014 in the
Journal of Applied Ecology
, Woinarski and colleagues showed that cats unleashed in an experimental enclosure can extirpate the long-haired rat, a native of northern Australia's savannas. And after dissecting a feral cat shot by a Kakadu ranger, Stokeld found in its stomach the remains of a dusky rat, four grassland mosaic-tailed rats, and two fawn antechinuses, a carnivorous marsupial. The non-profit Australian Wildlife Conservancy (AWC) estimates that every day in Australia, an astounding 75 million animals fall prey to roughly 15 million feral cats. But scientists doubt that the cats, which began fanning out across Australia soon after European settlers first arrived in 1788, are acting alone. The recent declines, says Chris Johnson, an ecologist at the University of Tasmania, Hobart, beg the question, ‘Why now?'

The answer may be changing fire regimes. Before Europeans arrived, Aboriginal Australians would burn small patches or pathways of bush to create conditions ideal for hunting or for moving more easily through the landscape. As Aboriginal populations dwindled, ‘nastier' fires that burned hotter and left bigger fire scars became the norm, says Jeremy Russell-Smith, a fire ecologist at CDU. In recent unpublished research using GPS tracking in north-western Australia, Sarah Legge, chief scientist at AWC, revealed that more widespread burning helps feral cats pick off critters exposed by the loss of ground cover.

To deprive the cats of their hunting grounds, AWC has implemented an intensive fire management regime at the Mornington Wildlife Sanctuary in north-western Australia's Kimberley region, intended to safeguard unburned vegetation. The reserve has also assiduously culled feral herbivores such as cattle, horses, and donkeys that thin the vegetation. As a result, native rodent and marsupial numbers have shot up fourfold in some habitats over just three years.

Curtailing feral cat populations is a more formidable challenge. One promising approach is an experimental bait containing para-aminopropiophenone, a chemical that converts haemoglobin in the bloodstream into methaemoglobin, which cannot transport oxygen. In a trial with the bait in central Australia last year, feral cat numbers fell by more than 50 per cent. However, trials in other areas didn't go so well, perhaps due to a greater abundance of live prey, which the cats favour over bait, or heavy rainfall that dampened the bait's appeal.

Some species may end up making their last stands on islands or in mainland arks fenced off from predators. In 2003, 64 captive-bred northern quolls were released on two islands free of cane toads off Australia's northern coast. A decade on, each island has several thousand quolls, says Dion Wedd, a curator at the Territory Wildlife Park in Berry Springs who was involved in the breeding program. Still, most scientists see such refuges as a last resort. Says Alaric Fisher, an ecologist at the Department of Land Resource Management: ‘We need [approaches] that work outside of fences.'

Global ‘roadmap' shows where to put roads without costing the earth

Field guide to the future

Aliens versus predators: The toxic toad invasion

Will a statin a day really keep the doctor away?

Elizabeth Finkel

Robert Browning, a California-based CFO of a life science company, is in his late 40s, has never been sick, is not overweight, and works out twice a week. But one day early last year when he went out for a walk he felt a sudden, strong pain in a small area of his right calf muscle. ‘It was as if someone had shot me in the leg,' he remembers. It was a muscle cramp so severe that he had to sit down, unable to walk or even stand.

After some research, Browning found that cramps can be a side effect of the only drug he was taking: Lipitor. His doctor had started him on the cholesterol-lowering statin a few weeks earlier after a test showed elevated cholesterol levels, raising his risk of heart attacks and strokes. Browning had never felt anything like that cramp before and was sure it wasn't related to his exercises. So when another one happened close to the same area two weeks later, he decided to stop the statins for good. He has not had a problem since.

Plenty of healthy people like Browning have been prescribed statins to lower their cholesterol. Now they are at the centre of a fierce medical debate. On one hand, doctors say cases like
Browning's are common and that debilitating side effects outweigh the benefits. On the other, researchers who analyse studies of hundreds of thousands of people under carefully controlled conditions say most of these ‘side effects' are not related to statins. In their view, the evidence is in: the benefits of taking statins to prevent coronaries and strokes outweigh the risks.

It's far from an academic debate. In 2014 health authorities in Britain and the US recommended widening the use of statins. These recommendations could see most men over 50 taking the drugs, amounting to a billion people worldwide.

Although statins are going off patent – Lipitor, the most popular, went off patent in 2011 – total revenues will keep rising, reaching one trillion US dollars by 2020 according to an estimate by John Ioannidis, a health policy expert at Stanford University.

Naturally, many are suspicious that the long arm of drug companies is behind the push to ‘statinise' much of the world's population. But many public health specialists believe the costs of widening the use of statins will be repaid in full by lowering the burden of heart attacks and strokes.

The debate has been explosive, rocking medical circles and reverberating in the media. The Australian TV show
Catalyst
even retracted two programs on the topic in May 2014. And yet it is nothing new. The debate over whether people should lower their cholesterol levels with statins has been incendiary since the drugs were introduced two decades ago.

There's no doubt that by lowering cholesterol levels statins save lives in people with clogged arteries, especially in those who've already suffered a heart attack or stroke.

But why wait: could taking statins prevent the blockage of arteries? Most heart attacks and strokes take place in people who've never had a symptom. That compelling logic has seen doctors prescribe statins to healthy people with high cholesterol for more than 20 years.

Until recently, the recommended threshold for prescribing statins was a 20 per cent risk of having a heart attack or stroke in the next ten years. That figure was based on a formula in which your doctor plugs in your cholesterol levels, blood pressure, smoking history, gender and age. But many doctors found their patients reported side effects – muscle cramps, back pain, nausea, memory loss and more. So was it really worth their while taking the drugs?

Studies on human beings are notorious for reaching different findings. They may be poorly designed or there may be unseen ‘confounding' factors. The prime adjudicator is an international group of independent experts who do not take money from the pharmaceutical industry called the Cochrane Collaboration. They slash their way through the academic thicket, decide which studies are worth analysing, and then do a so-called ‘meta-analysis'. Typically, the studies that are selected meet the gold standard: randomised placebo-controlled trials. Patients are randomly assigned to a treatment group that receives the real pill, or to a placebo group that receives a drug-free but otherwise identical pill.

Until 2011, Cochrane researchers found no clear benefits to using statins for ‘primary prevention' – in other words, to treating patients with no symptoms of an impending stroke or heart attack. Then in January 2013 they changed their tune.

Asymptomatic people who took statins were having fewer heart attacks and strokes and were less likely to need surgery to clear blocked arteries. Overall, there were fewer deaths. They concluded: ‘Statins are likely to be cost effective in primary prevention.'

The summary did not go unheeded. In January 2014 the American Heart Association published its new cholesterol guidelines. While they stressed the role of diet and lifestyle and the need to consider each patient individually, they also lowered the recommended threshold for using statins to a 7.5 per cent risk over the next ten years. Six months later Britain's National
Institute for Health and Clinical Excellence lowered its threshold for treatment from a 20 per cent risk to 10 per cent risk over the next decade. They estimated that even if only two million extra people took the drugs, 4000 heart attack deaths, 14 000 non-fatal heart attacks and 8000 strokes would be prevented – in health economic terms, a good trade-off for the estimated $60 million cost of using the off-patent drugs.

But not everyone was swayed by the Cochrane Collaboration's finding.

ABC TV journalist Maryanne Demasi had been watching with interest. A former PhD medical researcher, she had been researching the topic since 2010. During the filming of a story in a cardiologist's surgery she'd been astonished to find that a patient with a very high cholesterol level of 9mmol/L was not going to be put on statins. ‘His arteries are clean', the cardiologist had told her and added: ‘You should do a story on this.' Demasi started watching the ructions in the medical literature over the role of cholesterol in heart disease.

The Cochrane review of January 2013 was her lighting rod. It seemed at odds with other evidence that questioned the role of saturated fats and cholesterol in the development of heart disease. She also questioned the wisdom of automatically placing people on statins to reduce that risk. Many of her interviews were carried out with John Abramson, a health care policy lecturer at Harvard Medical School who acts as an expert in legal cases against drug companies for people who believe they have been harmed by statins.