Arctic tern's epic journey mapped

The Arctic tern's extraordinary pole-to-pole migration has been detailed by an international team of scientists.

The researchers fitted the birds with tiny tracking devices to see precisely which routes the animals took on their 70,000km (43,000 miles) round trip.

The study reveals they fly down either the African or Brazilian coasts but then return in an "S"-shaped path up the middle of the Atlantic Ocean.

The long-distance adventure is described in the US journal PNAS.

"From ringing, we knew where the Arctic tern travelled," said Carsten Egevang of the Greenland Institute of Natural Resources.

After setting out (yellow line) the birds pause in the North Atlantic (red circle) to feed. Going home (orange line), they follow the winds Total distance travelled 70,900km On southbound leg: 34,600km Daily progress south: 330km On northbound leg: 25,700km Daily progress north: 520km Within Winter grounds: 10,900km

"The new thing is that we've now been able to track the bird during a full year of migration, all the way from the breeding grounds to the wintering grounds and back again."

The avian world is known for its great migrations.

Albatrosses, godwits, and sooty shearwaters all undertake epic journeys. But none can quite match the Arctic tern's colossal trip.

Starting in August and September, this small bird - which weighs little more than 100g (3.5oz) - will head away from Greenland with the intention of getting to the Weddell Sea, on the shores of Antarctica.

It will spend about four or five months in the deep south before heading back to the far north, arriving home in May or June.

A team from Greenland, Denmark, the US, the UK and Iceland attached small (1.4g/0.05oz) "geolocators" to the animals to find out exactly where they went on this polar round trip.

The devices record light intensity. This gives an estimate of the local day length, and the times of sunrise and sunset; and from this information it is possible to work out a geographical position of the birds.

The geolocators were provided by the British Antarctic Survey (BAS).

"The use of these devices on seabirds is not only revolutionising our understanding of migration patterns, but the resulting data on distribution also help address the requirement to identify important biological hotspots," said Richard Phillips from BAS, a co-author of the PNAS paper.

With such a small bird, the trackers also need to be tiny

The first surprise is that the terns do not make straight for the Antarctic when they leave the Arctic, but make a lengthy stop-over in the middle of the North Atlantic, about 1,000km (620 miles) north of the Azores.

Here, they feed on zooplankton and fish to fuel themselves for the long journey ahead.

"We were able to compare biological productivity in the ocean from satellite imagery and we could see a high productive area that the birds will spend time in," said Mr Egevang.

"Even more importantly, it's the last high productive area before they enter tropical waters where we know productivity is low."

THE LONG DISTANCE FLIER Scientific name: Sterna paradisaea Average wingspan of 75-85cm Breeds in Arctic and sub-Arctic Lays eggs in small ground scrape Feeds on fish and crustaceans Birds live more than 30 years

The birds then head south along the coast of western Europe and western Africa before making a choice, either to continue hugging Africa or sweep across the Atlantic from the Cape Verde Islands to continue the journey along the Brazilian coast.

About half the birds that were tracked decided to take the South American path. It is not clear why, but the researchers believe wind might make either route seem favourable to the terns.

After spending their northern winter months in Antarctic waters, the terns then fly back towards the Arctic.

But rather than retracing their southward flight paths, the birds follow a gigantic "S" pattern up the middle of the Atlantic Ocean.

"This is completely new knowledge," Mr Egevang told BBC News.

"They make a detour of several thousand km but once we start comparing the route to the prevailing wind system, it makes perfect sense - moving in a counter-clockwise direction in the Southern Hemisphere, and clockwise in the Northern Hemisphere.

"It's just more energy-efficient for them to do that even though they are travelling several thousand more km than if they flew in a straight line."

World's biodiversity 'crisis' needs action, says UN

The UN has launched the International Year of Biodiversity, warning that the ongoing loss of species around the world is affecting human well-being.

Eight years ago, governments pledged to reduce the rate of biodiversity loss by 2010, but the pledge will not be met.

The expansion of human cities, farming and infrastructure is the main reason.

Speaking at the launch in Berlin, German premier Angela Merkel urged the establishment of a new panel to collate scientific findings on the issue.

Achim Steiner, executive director of the UN Environment Programme (UNEP), urged governments and their leaders to renew their commitment to curbing biodiversity loss even though the 2010 goal will be missed.

"The urgency of the situation demands that as a global community we not only reverse the rate of loss, but that we stop the loss altogether and begin restoring the ecological infrastructure that has been damaged and degraded over the previous century or so," he said.

The UN says that as natural systems such as forests and wetlands disappear, humanity loses the services they currently provide for free.

These include purification of air and water, protection from extreme weather events, and the provision of materials for shelter and fire.

With species extinctions running at about 1,000 times the "natural" or "background" rate, some biologists contend that we are in the middle of the Earth's sixth great extinction - the previous five stemming from natural events such as asteroid impacts.

Cash log

The UN Convention on Biological Diversity (CBD) was agreed at the Rio Earth Summit of 1992, alongside the climate change convention.

But it acquired its key global pledge during the Johannesburg summit of 2002, when governments agreed to achieve a "significant reduction" in the rate of biological diversity loss by 2010.

Conservation organisations acknowledge that despite some regional successes, the target is not going to be met; some analyses suggest that nature loss is accelerating rather than decelerating.

"We are facing an extinction crisis," said Jane Smart, director of the biodiversity conservation group with the International Union for the Conservation of Nature (IUCN).

"The loss of this beautiful and complex natural diversity that underpins all life on the planet is a serious threat to humankind now and in the future."

Mrs Merkel backed the idea of forming a scientific panel to collate and assess research on biodiversity loss, as the Intergovernmental Panel on Climate Change (IPCC) assesses evidence on climatic indicators.

"The question of preserving biological diversity is on the same scale as climate protection," she said.

"It would be sensible to have an interface between the politics and the science to integrate knowledge."

Nature loss 'dwarfs bank crisis'

A large on-going UN-sponsored study into the economics of biodiversity suggests that deforestation alone costs the global economy $2-5 trillion each year.

The UN hopes some kind of legally-binding treaty to curb biodiversity loss can be agreed at the CBD summit, held in Japan in October.

One element is due to be a long-awaited protocol under which the genetic resources of financially-poor but biodiversity-rich nations can be exploited in a way that brings benefits to all.

However, given the lack of appetite for legally-binding environmental agreements that key countries displayed at last month's climate summit in Copenhagen, it is unclear just what kind of deal might materialise on biodiversity.

Political football

The UN has been pursuing new ways of raising public awareness on the issue, including a collaboration with the Cameroon football team taking part in the African Nations Cup finals.

Many environment organisations will be running special programmes and mounting events during the year.

"The big opportunity during the International Year of Biodiversity is for governments to do for biodiversity what they failed to do for climate change in Copenhagen," said Simon Stuart, a senior science advisor to Conservation International and chair of IUCN's Species Survival Commission.

"They have the chance to make a major difference; and key to this will be halting species extinctions, the most irreversible aspect of biodiversity loss."

WWF is highlighting 10 species it considers especially threatened, ranging from commercially significant ones such as bluefin tuna to the Pacific walrus and the monarch butterfly.

In the UK, the national IYB partnership - hosted from the Natural History Museum (NHM) - is asking every citizen to "do one thing for biodiversity" in 2010.