I’ve just flown from London to North Carolina, a trip of around 6,200km. As flights go, it’s a pathetic one, a mere jaunt in the park compared to the epic voyage of the Arctic tern. Every year, this greatest of animal travellers makes a 70,000 km round-trip, in a relentless, globe-trotting pursuit of daylight. In summer, it spends its time in the sun-soaked Arctic and in winter, it heads for the equally bright climes of Antarctica. In its 30 years of life, this champion aeronaut flies more than 2.4 million kilometres – the equivalent of three return journeys to the Moon.
The Arctic tern’s marathon flight is fairly familiar, but estimating the length of such a massive trek isn’t easy. It would be charitable to forgive scientists for getting it wrong, given that they had to rely on observations at sea and capturing banded birds at different places. But few would have predicted just how wrong the textbook figures are. They typically suggest that the tern covers 40,000km in a year. The bird should be insulted – in reality, it flies almost twice that amount.
Its true itinerary has only just been revealed through the use of tiny tracking devices. Similar machines have already exposed the travel plans of larger seabirds like albatrosses, petrels and shearwaters. But these gadgets been too large and clunky to attach to smaller fliers – strapping a 400g recorder to a 100g bird isn’t going to give you an accurate picture of its flying abilities.
Carsten Egevang from Denmark’s Aarhus University changed all of that by developing tiny geolocators, less than 1g in weight. These locators can track the movements of migrating birds by recording the amount of light falling upon it at different points in its journey, and they’ve already been baptised by recording the entire migration of songbirds. Egevang strapped them to the leg of 50 terns, and managed to retrieve 11 of them the following season, when the birds returned.
Antarctica normally conjures images of white and blue, but the frozen continent can sometimes bear more unexpected colours. Take the Taylor Glacier – when geologist Griffith Taylor first explored it a century ago, he found a bizarre reddish stain that seemed to spill waterfall-like from the glacier’s snout. The area became evocatively known as Blood Falls.
The source of the blood-red colour is an underground saltwater lake that was trapped by the encroaching glacier at least 1.5 million years ago. The temperature of the water is -5 Celsius, but it’s so salty that it doesn’t freeze. It’s also rich in iron salts, which are slowly leaching the ice – these are the source of the distinctive red hue. Blood Falls is a rust glacier.
But it also houses another secret, which scientists from Harvard University have started to uncover – it’s home to an entire ecosystem of bacteria, trapped for millennia in conditions that could hardly be more inhospitable to life.
Neither water from the surface nor light from the sun penetrates the thick ice of Taylor Glacier to the lake lying 400 metres beneath. As the glacier slides overhead, trace amounts of gases might seep through, but nothing substantial. There’s hardly any oxygen dissolved in the water, and radioactive-dating of the little carbon suggests that it is incredibly old. But despite the extremely salty water and the lack of light, oxygen and carbon, the microbes have lived there for millions of years, using sulphate ions as their only source of energy.
The emperor penguin – caring parent, extreme survivor and unwitting movie-star – could be marching to extinction by the turn of the next century. In its Antarctic home, the penguins frequently have to deal with prolonged bouts of starvation, frosty temperatures of -40 degrees Celsius, and biting polar winds that blow at 90 miles per hour. And yet this icy environment that so brutally tests the penguins’ endurance is also critical to their survival. This is a species that depends on sea ice for breeding and feeding.
So what will happen to the emperor penguin as Antarctica’s sea ice shrinks, as it assuredly will in the face of a warming globe? Stephanie Jenouvrier from the Woods Hole Oceanographic Institution have tried to answer that question by combining the forty years of census data on a specific emperor colony with the latest models from the Intergovernmental Panel on Climate Change (IPCC).
The results are not encouraging. They suggest that the number of emperors in a large colony at Terre Adelie (where March of the Penguins was filmed) will fall from about 6,000 breeding pairs at the moment to a mere 400 by 2100. There’s even a one in three chance that the population will drop by 95%- a level described as “quasi-extinction”, when the population is so small that it’s unlikely to sustain itself.
Image copyright of Samuel Blanc