More frequent El Niño events in the future may
have surprising impacts on seabirds and some fish species, according to a study
from the University of California, Davis.
El Niños are unusually warm ocean conditions
that occur every two to seven years off the Pacific Coast, bringing with them
poor ocean productivity and sometimes catastrophic weather conditions. Fossil
coral records and climate change models indicate that El Niños occurred both
more and less frequently over the past 1,000 years than they do now, and
climate change may speed up or slow down their frequency in the future.
In a modeling study recently published in the
journal Theoretical Ecology, UC Davis researchers in the Department of
Wildlife, Fish and Conservation Biology wondered how changes in frequency of El
Niño and its more favorable, cool-water counterpart La Niña might affect
Brandt's cormorant. The seabird was selected as a model species because of its
known sensitivity to environmental changes.
"We expected that if you increased the
frequency of El Niños it would have a negative impact on the population,"
said lead author Annie Schmidt, a Ph.D. student at UC Davis during the time of
the study and currently a researcher at the nonprofit Point Blue Conservation
Science. "It turns out it was exactly the opposite."
The study's models indicated that doubling the
frequency of the El Niño-Southern Oscillation (ENSO) phenomenon, which includes
El Niño and La Niña, unexpectedly resulted in higher population numbers and a
lower chance of extinction for Brandt's cormorants.
That's because ENSO alternates between
unfavorably warm El Niño conditions followed by favorable, cooler La Niña
phases. Shorter, more frequent El Niños may mean the birds experience shorter
periods of poor conditions, with La Niña following to help them bounce back.
"If we speed things up, then we'll get
shorter bad and shorter good periods," said co-author Louis Botsford, a
professor in the UC Davis Department of Wildlife, Fish and Conservation
Biology. "If we slow things down, we get longer good and longer bad
periods. The latter is not good for this population because populations are
driven to low levels and go extinct when you hold them down for long periods of
By interspersing the failures with the
successes, the birds are better able to cope if El Niños become more frequent.
The study applies to other species, as well.
Brandt's cormorants can live for more than 20 years. Species with similar life
histories would likely respond the same way, the authors said. This could
include other long-lived seabirds and some fish, such as Pacific hake and some
Does this study indicate that climate change
could be beneficial for Brandt's cormorants?
"I wouldn't go that far," Schmidt
said. "This study is looking at a narrow scope of potential change. In
terms of overall effects of climate change, there are a lot of other factors
that come into play with this species and whole ecosystems that can be
What the study does indicate is the importance
of understanding how different species respond to different frequencies of
change in the environment. That is seldom considered when calculating the
probability of extinction.
The authors also point out that their study is
not predictive. Exactly how El Niño frequency may be altered by climate change
is uncertain. If the nature of the oscillation were to change, with unfavorable
El Niño conditions becoming more frequent or longer, while favorable La Nina
conditions did not change, the results could be very different.