Thousands of animals around the world are at risk of extinction. But not jellyfish - they're thriving in warm, polluted water.
- The world is in the midst of a mass extinction - the sixth time in the planet's history that species are experiencing a major global collapse in numbers.
- Up to 1 million species are threatened with extinction, many within decades, according to a United Nations report.
- Human activity is to blame: Habitats are being destroyed due to pollution, climate change, and deforestation.
- But one group of animals is benefiting: jellyfish. Rising ocean temperatures and overfishing are enabling jellyfish populations to grow at explosive rates.
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A growing body of evidence suggests the planet is in the midst of a sixth mass extinction.Between 500,000 and 1 million plant and animal species face extinction, many within decades, according to a report from the United Nations. Pollution, habitat loss, warming oceans, and other consequences of climate change are driving animal populations down on an unprecedented scale.Advertisement
But one group of creatures is bucking this ominous trend: jellyfish.
Jellyfish have roamed Earth's oceans for 500 million years. The bell-shaped underwater denizens can be found all over the world; there are some 4,000 species of them, according to the Smithsonian Institute.Over the past two decades, global populations of many jellyfish species have skyrocketed. Swarms of them, known as "jellyfish blooms," have become more common worldwide, forcing beach closures, causing power outages, and killing other fish.
Recent research has revealed that the increases in jellyfish populations can be linked to human activity, too. As greenhouse gases trap heat on the planet, oceans are heating up - they absorb 93% of that excess heat. Unlike many marine species, jellies can thrive in warmer water with less oxygen.
What's more, their natural predators, like turtles and sharks, are being overfished by humans.
Jellies are 95% water. The creatures don't have brains, stomachs, intestines, or lungs.
They move by rapidly contracting their mushroom-shaped bell to expel water, which propels them forward.Advertisement
Jellies are opportunistic feeders, meaning they'll ingest just about anything: microscopic plankton, crustaceans, and fish larvae are all fair game.
The absence of complex body parts allows jellies to adapt easily to changing ocean conditions.Advertisement
In the last 100 years, average ocean surface temperatures have risen by about 1.6 degrees Fahrenheit (0.9 degrees Celsius), according to the National Oceanic and Atmospheric Administration. Last year was the hottest on record for the seas.
Surprisingly, maritime shipping and undersea drilling industries also benefit jellyfish, since one of the creatures' reproductive stages, the polyps stage, requires them to settle on a hard surface.Advertisement
When inland rivers carry fertilizer run-off from agriculture to coastal waters, that can create competition-free buffets for jellies.
Overfishing is also fueling the global jellyfish proliferation.Advertisement
A 2012 study from the University of British Columbia concluded that "jellyﬁsh populations appear to be increasing in the majority of the world's coastal ecosystems and seas."
Groups of jellies are called "blooms" or "outbreaks."Advertisement
For one, they prevent swimmers and beachgoers from entering the water. Some 150 million jellyfish stings occur annually worldwide.
Some types, like the Chironex fleckeri species of box jellyfish, can kill a human in 3 minutes.Advertisement
In January, nearly 4,000 people were stung in one weekend by blue bottle jellies that drifted ashore in Queensland, Australia.
In large numbers, jellies can clog power-plant pipes and force them to shut down.Advertisement
In 2011, jellyfish overwhelmed the cooling system at a coal power plant near Hadera, Israel.
Jellyfish swarms can also be deadly for other marine creatures.Advertisement
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