By David Derbyshire, Science Correspondent
Electronic Telegraph
 A
FREAK "heatwave" in the Southern Ocean has halved the size of a colony of emperor
penguins living on the Antarctic coast, researchers report today.
The sudden
rise in temperatures in the late 1970s and early 1980s coincided with a sharp
drop in the survival rates of adult birds, a study has shown. The findings, published
today in Nature, highlight the dangers facing Antarctica's wildlife from global
warming over the next 100 years.
Dr Christophe Barbraud and Dr Henri Wirmerskirch,
from the National Centre of Scientific Research in Villiers en Bois compared the
size of a colony of penguins at Dumont d'Urville Station in Terre Adelie, Antarctica,
over 50 years with regional weather records.
Average winter temperatures
rose from minus 17.3C in the early 1970s to minus 14.7C by the late 1970s, reducing
the amount of sea ice on the coast south of Tasmania. Over the same period, penguin
numbers at the colony dropped to around 3,000.
The death rate was higher
for males than females. Although the population has since stabilised, there are
concerns that other colonies may have suffered similar declines. The highest death
rates coincided with a period of reduced sea ice between 1976 and 1980 and spells
of warmer sea surface temperatures.
"In years with high sea surface temperatures
emperor penguins probably have difficulties in finding food, which could increase
mortality," they report. Reduced sea ice was associated with a lower abundance
of krill - small shrimps which, along with fish and squid, are an important part
of the penguins' diet.
Extensive winter pack ice was also harmful for the
penguins, reducing the chances of a chick hatching successfully. But this disadvantage
was normally outweighed by better survival and more reproductive activity. Emperors
are the largest penguins, at 3ft 9in tall. |
