KARL DRURY/FAIRFAX NZ
BELLWEATHER: Adelie penguins number are booming in the chilly western Ross Sea.
Penguin numbers in Antarctica are plummeting, but in the
western Ross Sea - part of New Zealand's territory - there are more
adelie penguins than at any time in the past 30 years. Deidre Mussen
explores the reasons - and why we need to care.
Freezing air bursts into the helicopter as Peter McCarthy leans out
on its skid to photograph adelie penguins breeding below on Antarctica's
Ross Island. "It gets pretty cold," admits a ruddy-checked McCarthy, Antarctica
New Zealand's programme support supervisor, who is roped to the chopper
for safety.
From the air, the birds appear as regularly spaced black blobs that
dot the icy terrain, where they snuggle eggs on rocky nests. Over the course of a week, McCarthy aerially photographs 21 of the
22 adelie penguin breeding colonies in the western Ross Sea area,
including along Victoria Land's remote coastline and some offshore
islands, such as Ross Island, home to New Zealand's Scott Base.
Back in New Zealand, his shots are later fed into a computer, which
has a specialised programme to count the black blobs, although human
counters double-check penguin numbers visually.
The just-released final tally for last summer's census is a whopping
1.3 million adelie pairs, or 2.6m breeding birds, the most since the
joint Antarctica New Zealand and Landcare Research penguin census
project started 30 years ago.
That includes the Cape Adare colony, home to the largest adelie colony in Antarctica, with 428,516 breeding pairs. "That's a real huge boost, considering continent-wide there are
about 4 million breeding pairs," Landcare Research scientist Phil Lyver
says.
Yet-to-be-published American research indicates the western Ross Sea
has about a third of the world's adelies, based on a census across the
entire Antarctic continent. The population has averaged about 855,000
breeding pairs over the past three decades.
Penguin research, says Lyver, isn't all about cute fluffy animals.
"We're trying to use the penguins as what we call sort of a bellwether,
an indicator species for the ecosystem, and so, to do that, we need to
understand well how does the ecosystem or the changes in the ecosystem
actually influence the birds here."
Scientists believe changes in penguin numbers can alert the world
about Antarctica's health as global warming and fishing affect its icy
environment.
New Zealand needs to worry about such changes because Antarctica
drives our weather and directly affects our primary production-focused
nation, Lyver says.
Fishing in Antarctica is also big business, and has been implicated
in changes to penguin numbers elsewhere on the continent.
When New Zealand's adelie census began in the 1980s, population
numbers were high in Ross Sea colonies but started declining in the
1990s.
In 2000, the world's largest iceberg, B-15, broke off the Ross Ice
Shelf and part of it grounded to the north of Ross Island, near a large
adelie colony at Cape Bird, where it stayed for several years.
It had a major impact on penguin breeding because it forced them to
travel too far to find food for their chicks, causing breeding success
to plummet.
However, population numbers started increasing again once the iceberg floated away.
The penguin story is vastly different on the more northerly
Antarctic Peninsula and Scotia Sea, where populations have dramatically
reduced during the same period, according to international research.
That has been blamed on a combination of reducing levels of sea ice
because of rising temperatures and lower levels of krill, on which the
penguins feed. These factors may be driving the surge in penguins in the
Ross Sea area, Lyver says.
While sea ice extent and duration have decreased significantly
around the peninsula over the past three decades, it covers a much
larger area in the Ross Sea and lasts three months longer than 30 years
ago. "Sea ice is important in food productions and also as a platform
that allows the penguins to rest. It also gives security as the sea is
calmer within sea ice areas," he says. It is also vital as a krill creche, where baby krill develop into
penguin's favourite food. Studies clearly show krill abundance decreases
in direct proportion to sea ice vanishing.
Ultimately, Lyver says, more research is needed to link biological
sciences, such as New Zealand's adelie census, with physical studies of
factors like sea ice and climate, to truly understand what is going on
in the part of Antarctica nearest and dearest to New Zealand.
Scientists working at Cape Bird colony on Ross Island noted that
early snowfall and high winds probably had an impact on the birds'
breeding last summer, which had a success rate about half that of
"normal" years. Warmer weather means more snow will fall in Antarctica, and that directly affects the adelies' breeding success, he says.
They breed on land in nests made of rocks, unlike emperor penguins,
which lay in midwinter then balance their eggs and chicks on their feet
to keep them warm. More snow affects adelies' ability to keep their eggs warm. "It chills the embryo and kills the developing chick." Once the weather warms, snow melts and causes more problems for the
colony as the freezing water also cools eggs and can wash away eggs and
drown chicks.
Ironically, catching toothfish may help penguins because toothfish
are the top predator and their decrease means fewer silverfish are
eaten, which penguins also enjoy. However, krill fisheries may be
impacting on penguin numbers in other parts of Antarctica because they
remove an important penguin food.
Lyver warns that booming adelie numbers may be deceptive. "An
ecosystem where adelie penguins are going well is not necessarily a
healthy one. It's not wise to assume that increases in numbers means
that it is healthy. "It's easy to think everyone is Happy Feet down there. OK, adelie penguins are a bellwether, but a bellwether of what?"
http://www.stuff.co.nz/environment/10079702/Growth-in-penguin-numbers-cold-comfort