Wednesday, January 18, 2012

Wandering Albatross Riding the winds of climate change

We are stacking the climate dice against the survival of many species on planet earth. A few species may be able to ride the changes, at least temporarily. And so it is with the largest of birds, the wandering albatross, with some populations of this species able to take advantage, so far, of the changing winds of climate change. But for how long?

Global warming has caused the westerly winds in the Southern Ocean to increase in intensity and move poleward. The wandering albatross, with a three metre wing span, spends much of it's life soaring above the ocean searching for food, with the changes in the winds increasing it's foraging ability, breeding capacity and reducing it's conflict with commercial long line fishing operations.

A study published in 2001 found that there were differences in flight performance and foraging patterns between males, females and juveniles. Male wandering albatrosses tend to forage in the extremely windy sub-Antarctic and Antarctic zones south of the breeding colony in the Crozet Islands. Females tend to forage in subtropical and tropical waters to the north, where winds are lighter. Fledglings forage farther north in even lighter wind conditions than adults of either sex.

The species has been in steady decline through the twentieth century with a total population at 2010 estimated at about 8,000 breeding pairs. It is listed as vulnerable on the IUCN Redlist. It nests mostly on sub-antarctic islands. Breeding populations are found on South Georgia (20%), Prince Edward Islands (South Africa) (40%), Crozet Islands and Kerguelen Islands (French Southern Territories) (40%) and Macquarie Island (Australia) (approximately 10 pairs breeding per year), but albatross roam the high seas and are found right across the Southern Ocean, including Antarctic, subantarctic and subtropical waters. Juvenile birds remain at sea for 5 to 10 years before returning to their natal island to breed. They can live for up to 70 years.

The main threats to the species come from being caught and killed as incidental seabird bycatch in long line fishing such as for Bluefin Tuna and trawling fisheries, and introduction of alien species (such as rats or cats) which threaten breeding colonies. The accumulation of human pollution, plastic debris and fish hooks also has negative effects on albatross numbers.

The research is part of a long term study by biologists on the wandering albatross (Diomedea exulans) breeding in Crozet Islands, part of the the French Southern Territories located in the southern Indian Ocean (halfway between Madagascar and Antarctica). Data on the duration of foraging trips and breeding success has been gathered for 40 years, with information on foraging and body mass recorded for the last 20 years. The research team is made of of scientists from the French National Centre for Scientific Research (CNRS-CEBC) and the German Helmholtz-Centre for Environmental Research (UFZ).

"The wandering albatross Crozet population has decreased as a result of adult mortality on longline fishing in subtropical waters, especially females since they favour warmer subtropical waters in the north compared to the more southerly distribution of males" says Dr. Maite Louzao Arsuaga, who has been modelling albatross movement from 2009 to 2011 at the UFZ. "Due to the changing wind conditions, females are now foraging in more southward areas where such fishing is not that widespread".

As winds have increased in intensity and moved to the south, the flight speed of albatrosses increased resulting in them spending less time foraging. This has aided breeding success and both male and female birds have increased their body mass by about one kilogram, which corresponds approximately to one tenth of their total body weight. The scientists say the weight increase is due to shorter incubation periods on the nest, and also an adaptation to windier conditions.

The foraging movements of birds were plotted using miniaturised tracking devices. The results show that albatross have altered their search patterns following changes in wind conditions over the past two decades. Females used increasingly more poleward and windy areas for foraging. As a consequence their travel speed increased while the total distance covered during foraging flights did not change. "This means that they spend less time at sea while incubating the egg and thus the breeding success increases" explains Dr. Henri Weimerskirch of the French National Centre for Scientific Research (CNRS-CEBC).

The wandering albatross can live for 60-70 years. Chicks take a year to raise, so breeding usually occurrs every second year. It is at the top of the food web and provides a valuable indicator to scientists of the health of marine ecosystems in the southern ocean.

"Because the species has no natural enemies and is at the top of the food web, it is particularly well suited as an indicator of the health of marine ecosystems," says Dr. Thorsten Wiegand from the UFZ, who supervised the work of Dr. Maite Louzao. "This could help not only a single species, but the underlying biodiversity associated with pelagic key habitats to protect Southern Ocean. Moreover, we have developed methods of habitat modelling broadly applicable and can be used to assess changes in species distribution within the current global change scenario."

The research team identified key marine areas for conservation of wandering albatrosses in the southern Indian Ocean in a previous the paper - Conserving pelagic habitats: seascape modelling of an oceanic top predator (abstract) published in the Journal of Applied Ecology in 2010. This was the first map to support the future development of a network of priority protected areas in the southern part of the Indian Ocean, which are based on habitat predictions.

Unfortunately climate scenarios predict that westerly winds will move even further south by 2080 and wandering albatrosses might have to fly further to find optimal conditions for flying. This may then have a negative affect on albatross breeding and populations.

Biodiversity under threat

There are a thousands of local stories about the threat to species biodiversity. From San Francisco Mayor Gives Death Sentence to Endangered Frogs, to penguins facing an uncertain future.

While global warming is increasing temperatures, exacerbating extreme weather events, and reducing biodiversity, many species will be losers, such as many lizard species, and iconic species such as the Australian koala.

Recent scientific studies have identified that Species biodiversity is under threat from the velocity of climate change, and that Climate change and habitat loss threaten biodiversity, with the extinction rate underestimated. Marine scientists have been warning that our Oceans are at high risk of unprecedented Marine extinction.

It all comes down to the explosion in the human population and the consumerist lifestyle based upon a system of production and energy that has taken no account of the cost of pollution to ecosystems and other species. Human industrialisation has caused the carbon pollution that is changing our climate. But worse is yet to come.

If we do not tackle the issue of carbon pollution quickly the impacts of climate change will escalate. Human health is already threatened in the increase in extreme events, and we have only seen 0.8 degrees celsius of global warming so far. Imagine the world at 5 degrees Celsius which is where the world is heading by 2100 with business as usual according to the Climate Interactive scoreboard. Once climate feedback processes kick in, we could be in for a very rough ride. Scientists studying climate sensitivity say the paleoclimate record points towards potential rapid climate change.

Sources:

  • Adapted from Helmholtz-Centre for Environmental Research (UFZ) media release, 12 January 2012 - Largest seabird alters their foraging due to climate change
  • Henri Weimerskirch, Maite Louzao, Sophie de Grissac, Karine Delord in Science, 13 January 2012 - Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits(abstract) - DOI: 10.1126/science.1210270
  • Photo: David Gremillet/CNRS Copyright Helmholtz-Centre for Environmental Research (UFZ) used for non-commercial purposes - Researchers on Crozet fitting a transmitter on a wandering albatross.