Climate Change Boosts Galapagos Penguin Population
Posted by Eric Haun
Monday, August 03, 2015, 11:19 AM
A new study compared sea surface temperatures with endangered
Galapagos Penguin population counts and found that the penguin
population doubled while waters cooled around their nesting islands.
(Courtesy of Snowmanradio/Flickr)
New study finds shifting winds and ocean currents helped double endangered Galapagos Penguin population
Shifts in trade winds and ocean currents powered a resurgence of
endangered Galapagos Penguins over the past 30 years, according to a new
study led by researchers at the Woods Hole Oceanographic Institution
(WHOI). These changes enlarged a cold pool of water the penguins rely on
for food and breeding—an expansion that could continue as the climate
changes over the coming decades, according to the study.
The Galapagos Islands, a chain of islands 1,000 kilometers west of
mainland Ecuador, are home to the only penguins in the Northern
Hemisphere. The 48-centimeter tall black and white Galapagos Penguins
landed on the endangered species list in 2000 after the population
plummeted to only a few hundred individuals and are now considered the
rarest penguins in the world.
Most of the penguins live on the archipelago's westernmost islands,
Isabela and Fernandina, where they feed on fish that live in a cold
pool of water on the islands’ southwestern coasts. The cold pool is fed
by an ocean current, the Equatorial Undercurrent, which flows toward the
islands from the west. When the current runs into Isabela and
Fernandina, water surges upward, bringing cold, nutrient-rich water to
the surface.
New research suggests shifts in wind currents over the past three
decades, possibly due to climate change and natural variability, have
nudged the Equatorial Undercurrent north. The changing current expanded
the nutrient-rich, cold water farther north along the coasts of the two
islands, likely bolstering algae and fish numbers in the cold pool. This
allowed the penguin population to double over the past 30 years,
swelling to more than 1,000 birds by 2014, according to the new study.
Climate change could further shift wind patterns and ocean
currents, expanding cold water further north along the coasts of Isabela
and Fernandina and driving fish populations higher, according to the
new study.
Penguins, as well as other animals like fur seals and marine
iguanas that feed and reproduce near the cold waters, may increase in
numbers as the northwestern coasts of the islands become more habitable,
said the study’s authors. They noted that wind and ocean currents could
also return to earlier conditions, leading to a decline in penguin
populations.
"The penguins are the innocent bystanders experiencing feast or
famine depending on what the Equatorial Undercurrent is doing from year
to year," said Kristopher Karnauskas, a climate scientist who performed
the research while at WHOI, and lead author of the new study recently
accepted in Geophysical Research Letters, an American Geophysical Union
journal.
The new findings could help inform conservation efforts to save the
endangered penguins, said the study’s authors. Increasing efforts on
the northern coasts of the islands and expanding marine-protected areas
north to where the penguins are now feeding and breeding could support
population growth, the study’s authors said.
Karnauskas notes that the vast majority of marine organisms will be
negatively affected by the rise in ocean temperatures and acidification
that are expected to occur across the globe as a result of climate
change.
"With climate change, there are a lot of new and increasing
stresses on ecosystems, but biology sometimes surprises us," said
Karnauskas. "There might be places—little outposts—where ecosystems
might thrive just by coincidence."
The Galapagos Penguin population tenuously hangs onto the islands
that so enthralled Charles Darwin during his visit in 1835. The penguins
once numbered around 2,000 individuals, but in the early 1980s a strong
El Nino – a time when sea surface temperatures in the tropical Pacific
are unusually warm – brought their numbers down to less than 500 birds.
Dogs, cats and rats introduced to the islands also stymied the penguin
population by attacking the birds, disturbing their nests, and
introducing new diseases, according to previous research.
Despite these setbacks, the penguins gradually increased in number
in the following decades, according to local bird counts. Researchers,
interested by the increase in penguins, noted that the birds remained
near the coldest stretches of water. Nearly all of the Galapagos
Penguins live on the western coasts of Isabela and Fernandina, and
two-thirds of them huddled near the coldest waters at the southern tips
of the islands, according to previous research.
The study's authors wanted to know whether the growing numbers of
penguins were related to local changes in ocean temperature. They
combined previously-collected penguin population data from 1982 to 2014
with sea surface temperature data from satellites, ships and buoys for
the same time period.
They found that the cold pool, where sea surface temperatures are
below 22 degrees Celsius, expanded 35 kilometers farther north than
where it was located at the beginning of the study period. In the 1980s
the cold water pocket reached only the southern halves of the western
coasts of Isabela and Fernandina. By 2014, the cold water pocket
extended across the entire western coasts of the islands.
A shift in trade winds and underwater ocean currents likely caused the Galapagos cold pool expansion, propose the authors.
Trade winds blow surface ocean waters from the southern side of the
equator to the northern side of the equator. As surface waters pile up
in the north, the water at the bottom of the pile is squished south,
nudging the Equatorial Undercurrent—a cold current that flows roughly 50
meters under the ocean surface—south of the equator.
Likely due to a combination of natural variation and human-caused
climate change, trade winds west of the Galapagos slackened during the
study period, lessening the pressure pushing the Equatorial Undercurrent
south, according to the new study. Consequently, the ocean current
gradually shifted north, increasing the amount of cold water coming to
the Galapagos Islands, according to the study’s authors.
Satellite images showed that this expanded pool of cold water
likely encouraged the growth of phytoplankton, according to the new
study. This increase in ocean algae attracted fish to the area— the main
entrée for Galapagos Penguins, suggest the authors. The largest pulses
of cold water reached the islands from July through December, coinciding
with the penguins’ breeding season. The bountiful fish helped the birds
successfully reproduce and feed their young, according to the new
study.
Models indicate trade winds will continue to abate in the future as
the climate warms, Karnauskas said. This could cause the undercurrent
to continue to move north, expanding the Galapagos cold pool and
possibly further raising penguin populations, he said. Other animal
populations like the endangered Galapagos fur seal and the marine iguana
also may profit from the prolific amount of food in the Galapagos cold
pool, according to the study’s authors.
Wind and ocean currents could also possibly return to where they
were in the 1980s, compressing the cold pool and possibly leading to a
decline in penguins, Karnauskas added.
The new study shows how large-scale changes in the climate can act
locally, said Michelle L'Heureux, a meteorologist with the National
Oceanic and Atmospheric Administration's Climate Prediction Center in
College Park, Maryland, and not an author on the new paper.
"While it is important that we focus on the big picture with
climate change, it's really the small scale that matters to the animals
and plants that are impacted," she said.
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A satellite image of the Galapagos Islands in 2002. Almost all of the Galapagos Penguins live along the western coasts of Isabela and Fernandina and two–thirds of the birds reside along the southwestern bulge of Isabela. (Image: NASA)
