This asset was created based on the National Geographic Magazine article that shares the same title. Written by Hillel J. Hoffman, the article offers insights into the author’s interactions with paleontologists and scientists while exploring the Black Triangle and Karoo regions. The primary goal is to uncover a deeper understanding of the Permian extinction and its subsequent consequences.

"Welcome to the Black Triangle," said paleobiologist Cindy Looy. Our van slowed to a stop in the gentle hills of the Czech Republic. The Black Triangle gets its name from the coal burned by nearby power plants. Decades of acid rain from power-plant emissions have devastated the region's ecosystems. For months I'd been on the trail of the greatest natural disaster in Earth's history. About 250 million years ago, at the end of the Permian period, something killed off 90 percent of the planet's species. Less than five percent of the animal species in the seas survived. On land nearly all the trees died. Looy had told me that the Black Triangle was the best place today to see what the world would have looked like after the Permian extinction. We saw the first signs of death as we walked into the hills — hundreds of fallen logs lay hidden in the undergrowth. No birds called, no insects hummed. The only sound was the wind through the weeds. "The forest that grew here a few decades ago contained dozens of species of plants," said Looy. "Now there are only a few grassy species." Still, I was surprised by how healthy and green the treeless hills appeared. Looy believes that the Permian extinction was caused by acid rain following a massive release of volcanic gases. She is like a homicide detective studying pollen and pine cones for clues about what happened millions of years earlier. "You could say we're working on the greatest murder mystery of all time," she said.

Who dunnit?

Looy is one of many scientists on the case. They are trying to identify the killer responsible for the largest mass extinction that has struck the planet. To understand this extinction, I wanted to get a sense of its scale — and for that, I had to go to South Africa. I joined Roger Smith, a paleontologist at the South African Museum, and we drove across a treeless stretch of land known as the Karoo. If we had driven here before the Permian extinction, we would have seen animals as abundant and varied as in today's Serengeti. Most would have belonged to a group known as synapsids. They looked like a cross between a dog and a lizard, and for more than 60 million years they were Earth's dominant land vertebrates. They filled the same ecological space as their successors, the dinosaurs. Smith slowed, rolled down the window, and pointed to a horizontally banded cliff. "See that road cut?" he asked. He explains the fossil record here reveals the transition between the Permian and Triassic periods. The fossils embedded in the rock indicate that synapsids took a savage hit at the end of the Permian. Their remains are abundant on the lower layers, but higher up they dwindle and disappear. Plants were also hit by the extinction. To see evidence of the destruction of the world's forests I travel to the Italian Alps. I joined a research team led by Henk Visscher of the University of Utrecht. We visited exposed fossil beds revealing the transition from the Permian to the Triassic. Here researchers showed me evidence of a great die-off of trees. The older, lower levels of the fossil record contain a great deal of pollen from conifers from before the extinction event. In rocks from the Permo-Triassic boundary, however, the pollen has disappeared, replaced by fossilized fungi. "We think it's a wood-decaying fungus," says Looy, who works with Visscher. "When a tree dies, it falls. As it decays, fungi grow into it from spores on the ground, decomposing it." Visscher's team has found elevated levels of fungal remains in Permo-Triassic rocks from all over the world. Their conclusion: Nearly all the world's trees died suddenly. Evidence of the Permian catastrophe is abundant and clear, but what was the culprit? Researchers are looking for clues in the geology and chemistry of Earth and its oceans.

Prime Suspects

Gregory Retallack is a geologist at the University of Oregon. His prime suspect for the Permian extinction is an asteroid smashing into the Earth. A team of researchers recently found what may be that impact's footprint below Australia: a 120-kilometer-wide (75-mile-wide) crater. The impact would have sent billions of particles into the atmosphere, Retallack says, blocking out the sun for months. Temperatures would have dropped, killing plants and photosynthetic plankton, the base of the food chain. Herbivores would have starved, as would the carnivores that feed on plant-eaters. Other Permian detectives suspect the killer oozed up from the sea. For years scientists have known that the deep ocean lacked oxygen in the late Permian. Most life is concentrated in shallow water, in places like reefs. In 1996, English geologists Paul Wignall and Richard Twitchett reported evidence of oxygen depletion, or anoxia, in rocks that formed under shallow water at the time of the extinction. For whatever reason, ocean currents may have stopped circulating. Anoxic water could have built up and smothered marine life. Another leading suspect is a deadly period of volcanic activity. Eruptions would have spread a kilometers (miles) deep layer of lava across Siberia. As volcanic gases poured into the skies, they would have generated acid rain. Particles would have blocked sunlight and cooled the planet. Glaciation would have reduced the volume of water in the ocean, storing it as ice. Sea level would have dropped, killing marine life and severely reducing diversity on sea and land.

The Truth May Be Untidy

Each scientist I met left me thinking that he or she was a clue or two away from solving the crime. However, as Doug Erwin of the Smithsonian cautioned me, "the truth is sometimes untidy." Erwin suspects there may have been multiple killers at the end of the Permian. Maybe everything — volcanic eruptions, an asteroid impact, and oxygen-starved oceans — went wrong at once. Now humanity is creating a new mass extinction, wiping out countless species. Will life be as resilient this time? I think about what I have learned in my research. I conclude that if life can survive the Permian extinction, it can survive anything.