Most of us think of climate change in terms of global warming, but there are also natural variations in the Earth's climate which influence the penguin survival and breeding success. The El Niño/Southern Oscillation (ENSO) event is a medium-term climate variation that effects penguins in temperate waters. Penguins in the Antarctic and sub-antarctic regions don't appear to be directly affected by ENSO, but may be being impacted by the long-term climate change that is slowly warming our planet.
El Niño (Spanish for "the boy child") is the term given to the warm portion of the ENSO cycle and specifically refers to the warming of the Humbolt current that sweeps up the west coast of South America (usually around Christmas and hence the reference to the boy child) and across the equatorial Pacific. The cool phase is known as La Niña (the girl). These phases may be of varying intensity and may not impact the climate the same way in all locations. For example, in New Zealand, sea surface temperatures actually drop during El Niño events and increase under La Niña. For more information on ENSO, look at the NOAA El Niño theme page or look up todays sea surface temperature anomaly from NOAA's Climate Prediction Centre.
The global greenhouse
Scientific evidence indicates that the Earth's surface temperature is slowly rising. The oceans are getting warmer and higher as polar ice melts. This is having an impact on our weather patterns and may be contributing to the decline in the crested penguin populations of the sub-antarctic region. Carbon dioxide emissions, largely from the use of fossil fuels, appear to be a significant cause of global warming. Worldwide efforts are being made to reduce CO2 emissions, however some large industrialised countries have shown reluctance to do so because of the cost to their economies.
The temperature of the oceans directly impact marine productivity and hence the abundance and breeding success of the penguins food supply - fish, squid and krill. Generally, cooler waters increase food abundance and warmer waters decrease it. These variations in food availability can have a dramatic impact on penguin breeding success and chick survival and sometimes results in the starvation of adults. Chloroplyll A densities measured by satellite are a useful measure of marive productivity.
Some species, for example yellow-eyed and blue penguins, are subject to periodic large-scale adult mortality not due to starvation. Bio-toxins produced by algal blooms and accumulated in fish are usually to blame. Abnormal local sea conditions are more likely to be the cause than any wide-scale climate event.
How do we know this?
Satellite imagery has vastly increased our knowledge and understanding of the Earth's climate. However, to understand how this affects penguins, hands-on work is needed. To determine what penguins eat, it is necessary to capture them and see what is in their stomachs. This is done by inserting a tube down the throat and flushing the contents out with water. This procedure, called stomach flushing, doesn't harm the penguin, but neither the penguin or the researcher enjoys the experience! Dead penguins are often dissected to determine the cause of death and often provide useful information on diet, diseases and parasites.
Recently the development of satellite global positioning loggers with temperature recorders that can be fitted to penguins has made the three-dimensional temperature mapping of waters the penguins use possible.
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