In 1982, there were 2 million king penguins on France’s Île aux Cochons island in the Indian Ocean. Today, there are around 200,000, a nearly 90% drop in population size, according to researchers at the Centre for Biological Studies in Chize, France.
The decline could be due to various factors, the researchers speculate, but the dramatic nature of the shift is cause for alarm.
The researchers determined the dire situation by taking satellite images of the island and comparing it to earlier photographs. The recent images show a much smaller penguin population and far more vegetation, indicating that grass and other plants were able to regrow in previously trampled areas.
Take Action: Ensure All Communities Can Withstand Climate Disaster
The most likely reason for the falling population has to do with climate change.
For the past several decades, ocean temperatures have been warming and extreme weather events have been getting worse. The El Niño weather pattern in certain years probably pushed fish and squid populations into colder waters outside the penguins’ feeding range, causing the birds to starve, the researchers report.
Since climate change warms waters on a gradual basis, it could drive these marine species outside of the penguins’ reach on a permanent basis, causing an existential crisis, according to the Guardian.
The researchers also speculate that avian cholera could have ravaged the population, as it has done with other species of birds in the past. Another reason for the decline could be that the penguin population became unsustainably large and then collapsed as food resources became scarce.
Read More: Scientists Just Found 1.5 Million More Penguins in Antarctica
Finally, invasive species such as rats or cats may have entered the island and killed large numbers of penguins or eaten their eggs, the Guardian notes.
The researchers plan to investigate the cause of the decline in the years ahead, but the preliminary analysis supports a growing consensus that the world is becoming inhospitable for animals.
In fact, a recent analysis found that humanity has destroyed 83% of all wild animals and half of all plants, and biologists are in broad agreement that the sixth mass extinction in the planet’s history is currently underway.
Read More: Fishing Companies Are Trying to Hide How Penguins Are Showing Up Dead in Their Nets
King penguins are currently described as “least concern” by the International Union for the Conservation of Nature and are deemed to be increasing in numbers.
That status may have to be revised in light of this report and others.
Earlier in the year, another report argued that king penguins in Antarctica could disappear by the end of the century because of climate change.
Reversing this decline requires countries to reduce their greenhouse gas emissions and achieve the Paris climate agreement.