Manila, Philippines. Friday, December 10, 1999.

President Joseph Estrada is meeting with senators and the discussion is tense. Estrada took office during a time of major economic decline and now, a year and a half later, the debt and unemployment are still growing. His popularity falls while opposition to his policies rises. In August, tens of thousands of hungry Filipinos swarmed the streets in protest against his probusiness agenda, demanding he focus instead on the needs of the poor. “Whether removed by force or by the broad coalition arrayed against him,” US analysts said a few weeks earlier, “Estrada is unlikely to fulfill his six-year term in office.”

In the midst of the meeting, in mid-sentence, the lights go out. Half the country has just lost power. Have rebels sabotaged the power system? Is this a coup d’état? Estrada’s predecessor endured seven failed coup attempts; the president before that was successfully removed by popular revolt.

Estrada waits, blind. Time passes slowly, ten agonizing minutes, every second of which he expects to hear the sounds of fighting, expects to be surrounded by rebels, expects to find a gun pointed at him.

But when the lights come back on, he’s still president. He tries to calm the public the next day, explaining that the cooling system failed at the country’s largest coal power plant, Sual Power Station, when its water intake was clogged. It took seven hours to fix the problem, he says, because workers had to clear, by hand, hundreds of tons of brown and black slime—the power plant had been assaulted by millions of jellyfish.

It’s not only in the Philippines that jellyfish are a problem. These otherworldly creatures are amassing around the world, doing far more than ruining family holidays with beachside stings. Jellies are wreaking havoc, causing billions of dollars of economic damage. They’re shutting down power plants, capsizing boats, disrupting underwater mining, disabling aircraft carriers, destroying commercial fish farms, and taking over entire ecosystems.

A jellyfish makes for an unlikely monster. We were once even unsure whether it was animal or plant. Floating in the ocean, it rides the currents without resistance, kelp-like tentacles streaming listlessly behind. The radial symmetry of its body suggests it might be flora—alive, but free from the burdens of volition—moving only at the wave’s whim. But then its body suddenly contracts, rhythmically, the pulse of a ghostly heart. Clearly, this is fauna. Primordial and alien, but animal.

The creature’s limpid skin teases with the promise of secrets exposed, but inside there’s nothing to see. No bones, no blood, no guts; no ears, no nose, no blinking eyes; no lungs or gills; no front and no back. A jellyfish is a sack within a sack. The outer sack, the umbrella, is a skin that absorbs oxygen and separates the animal from the world, a skin that holds a jelly-like substance called mesoglea, but no apparent organs. The inner sack, the subumbrella, ingests food and expels new jellyfish. There is only one way in or out of a jellyfish; its mouth is its anus is its mouth. Food, excrement, sperm, eggs, all pass through the same versatile orifice.

There are over 2000 species of jellyfish. Some are enormous, eight feet in diameter, with tentacles longer than a blue whale. Some are as small as a grain of sand. Most are harmless to humans and, seen from behind the safety of aquarium glass, all are beguiling, more mystery than menace. After all, it’s a stretch to say that these blobs of goo even hunt for their food. Few can swim anywhere other than up or down, and even that much they do slowly. Most of them don’t have what we’d consider eyes and simply stumble into their meals, relying on providence to sweep hapless prey into their waiting tentacles. Such a bumbling predator has none of the shark’s toothy menace, yet sharks kill fewer humans each year than do jellyfish. In 2012, seven people were killed by sharks, worldwide. In the Philippines alone, jellyfish annually kill as many as forty people.

A box jellyfish’s home is in the warm, tropical waters of the Philippines, New Zealand, and Australia, where, instead of drifting, it hunts. It has true eyes with cornea, pupil, lens, and retina that, like ours, form images. It can swim as fast as a human walks, purposefully. Of all the jellies, it has the closest thing to what we’d call a brain: bundles of nerve nets hidden along the inner margin of its bell that connect to receptors for light, touch, gravity, and smell—a networked system it uses to sense the oxygenation and salinity of water, to know pressure and depth, and to detect and avoid nearby obstacles. Pale blue and transparent, a box jellyfish is cube-shaped, with one to fifteen tentacles at each of its four corners, tentacles up to ten feet long, all of them bristling with thousands of cnidocytes, cells containing poisonous harpoons that shoot out with 40,000 Gs of force to hit their target in less than a microsecond, one of the fastest movements in nature. The sting of one species of box jellyfish, Chironex fleckeri, the sea wasp, can kill an adult human in less than three minutes. It is the world’s most venomous animal.

It may sound like something out of a 1960s B-movie, but some scientists see a coming marine apocalypse, an oceanic coup orchestrated by mobs of mutinous jellyfish. Marine biologist Lisa-Ann Gershwin says jellyfish “could crash the world’s fisheries, outcompete the tuna and swordfish, and starve the whales to extinction.” She thinks we’re headed for a future where the seas are filled with jellyfish and little else. In some parts of the world, we’re already there.

Through accidents of geology, for thousands of years much of the Black Sea has been low in oxygen and high in hydrogen sulfide, effectively toxic. Though few areas of the sea support life, even that small portion has been an important source of food and income to surrounding countries; boats used to pull hundreds of thousands of tons of fish out of the water each year.

Then, around 1982, the jellyfish Mnemiopsis leidyi, also known as the warty comb jelly or sea walnut, appeared. By 1998, the fish were gone, the local economies were crippled, and the sea walnut was the Black Sea’s dominant species. Today, 95% of all the organisms in the Black Sea, by weight, are jellyfish, and it’s not the only place threatened with jellification; San Francisco Bay sees a new marine species added to its ecosystem every three to four months. Off the coast of Angola, jellyfish have built an all-encompassing killing field, a curtain of stinging slime that covers 30,000 square miles of ocean. Jellyfish are even in Antarctica, where they may eventually replace penguins.

Jellyfish are launching their sorties by hitching rides to all the world’s ports, to Manila, to the Black Sea, to San Francisco, to Angola, hidden in the ballast water of tankers, moving to ecosystems where they have no natural predators. Flexible eaters, they feed on the eggs and larvae of native fish, as well as the plankton that feed those fish, even the fish themselves, quickly wiping out their competition. Toxic environments aren’t a problem—a jellyfish needs much less oxygen than other fish and it’s immune to most toxins, having little tissue in which to store them. A jellyfish’s biggest weapon, however, is sex.

Like the butterfly that spawns from a caterpillar, a jellyfish has two forms. One form, the polyp, a translucent tube with a frilly frond, roots itself on the ocean floor, flowerlike. The other form, the medusa, named after the Greek monster whose venomous hair hung from her head like tentacles, floats freely in the water. Unlike the butterfly, each of a jellyfish’s forms can reproduce. Polyp babies, ephyrae, grow up to be medusae; medusa babies, larvae, grow up to be polyps.

When the ephyrae produced by polyps are sexually mature they look like what we think of when we think of jellyfish: round bells with long tentacles. A medusa spawns daily, usually at the same time, filling the water with thousands of new eggs, churning out armies of jellyfish. Each soldier is able, each day, to eat many times its own body weigh. It’s these ravenous hordes of medusae that become soldiers in World War J, assaulting power plants and ravaging marine life.

Polyps, meanwhile, are jellyfish generals, sending a seemingly endless supply of fresh troops into battle. Polyps look like plants and act like seeds, lying dormant for years or even decades until conditions are right, conditions in which to bud, one by one, dozens of new ephyrae. Polyps can also reproduce asexually, cloning themselves to make even more polyps. When jellyfish—medusa—populations wane, polyps remain; hidden, waiting. Such an immense reproductive capacity has made the jellyfish a threat in the Philippines and around the world, where they’re reproducing explosively, creating plagues of biblical proportions.

If there’s no intent behind this jellyfish takeover—they’re more zombie horde than evil genius—is it going too far to call the jellyfish a monster? When a creature is colonizing every corner of the planet, invading and taking over ecosystems, killing all its competitors, wiping out entire species, reproducing without limit, fouling the water with its waste, and making vast areas of the planet inimical to life, what else would you call it?

How about human?

Sual Power Station in the Philippines, the one that left Estrada in the dark, gets its water from Lingayen Gulf, where, along with the jellyfish, more than a hundred fishermen pack into each square mile of water. Over the last half century, fish hauls in the country have increased by almost 1600%, making the Philippines one of the world’s largest producers of fish.

Along the way, they’ve created the perfect environment for jellyfish. Commercial boats drag trawls along the bottom of the sea to rake in the fish; the locals use dynamite and cyanide. Both approaches have devastated the fish population and, to compensate, the country has shifted to aquaculture. They now farm more fish than they catch. Farmers have cut down nearly all the archipelago’s trees to make way for fish ponds, a practice that has led to severe erosion.

By turning fish into food and money, the human population has quadrupled in the last fifty years; their sewage flows into the sea, along with eroding earth, heavy metals from mining operations, waste from fish farms, and chemical fertilizers from human farms. As a result, the Lingayen Gulf is increasingly warm, acidic, toxic, and low in oxygen, with few large fish—but plenty of plankton and jellyfish—and the Philippines are not an outlier. The same song, with minor variations, is playing in China, Europe, Africa, the US, and Antarctica. The jellyfish are just doing what jellyfish do, and we’re the ones making it possible.

It’s not through dumb luck that jellyfish can turn almost any situation to their advantage, including the ones we’ve given them. Jellyfish are successful because they’re weeds—hardy, flexible, and opportunistic creatures that exploit disturbed environments, reproducing aggressively, surviving under the worst of conditions and thriving under most. They’ve developed their simple but effective biology over hundreds of millions of years, surviving five mass extinctions, including the Permian–Triassic event that wiped out 97% of all marine species. Jellyfish may be our planet’s greatest evolutionary success.

There’s a way, perhaps to put things into perspective. Raise your arm until it parallels the floor, extending it out in front of you, palm up. Imagine that the length of your arm represents a timeline of the history of the planet. The trailing edge of your shoulder is Earth’s beginning, the very formation of our world, four and a half billion years ago. The very tip of the fingernail of your middle finger is the current moment. Life began—simple unicellular organisms like bacteria and algae—where your pectorals converge with your deltoid and bicep above your armpit. The bend where your middle finger meets your palm is when jellyfish appear in the fossil record, before the Cambrian explosion. For the next 100 million years jellyfish ruled the sea. They were kings of the ocean and so kings of the earth, for during this time there were neither animals nor plants on land; the earth was barren and rocky, desolate, Mars-like. Midway between the second and third joint of your middle finger, the dinosaurs appeared. An inch further on they went extinct. And here we are, at the tail end of history. Run a file lightly across your fingernail and you have erased all of human existence. Here we are, living a waking dream, the dream of the jellyfish, the dream to make the seas Cambrian again, as if restoring the once and future king to his watery throne was our one true purpose. Here we are, waiting. Blind.