The toxic lake left behind after the Berkeley Pit copper mine shut downGetty / Richard Cummins

In late November, a flock of migrating snow geese landed in a lake in Butte, Montana. Soon, they began to die. Because what they landed in was the Berkeley Pit, a Superfund site filled with acidic and metal-laden toxic waste from copper mining. The lake was “white with birds;” thousands died. Weeks later, as the story has gone viral, officials are still counting.

The Berkeley Pit had killed migrating geese before. “It was a shock to hear it happening again, on a much larger scale,” says Andrea Stierle, who, along with her husband Don, has been studying the Berkeley Pit for more than three decades. In 1995, over 300 migrating geese landed in the pit and died from ingesting the toxic water. The Stierles were chemists at nearby Montana Tech at the time, and they were in search of microbes living in the toxic waste water that could make antibiotics and other useful substances. That arrival of the first flock of geese changed the microbial makeup of the Berkeley Pit and likely the outcomes of Stierles’ research, too.

The story of the Berkeley Pit isn’t a simple story of ecological disaster.

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There wasn’t supposed to be a lake here, let alone a toxic one. But in the Cretaceous period, when Montana was dotted with volcanoes, lumps of magma rose up through the Earth’s crust, bringing with them veins of ore rich in copper, silver, and gold. Seventy-five million years later—give or take a few million—humans stumbled on the precious metal near Butte. They came with their picks and axes, hollowing out tunnels for copper that built America’s electric grid in the early 20th century. When they dug out as much copper as they could from tunneling, they decided to turn the mine into an open pit.

Then there was a pit, but there was still no water. Pumps kept groundwater out of the active mining site. When the mine shut down on Earth Day, 1982, the pumps shut down, too. The pit began to fill up with groundwater contaminated by toxic mining waste. Today, the artificial lake is a mile wide and a mile-and-a-half long.

Andrea and Don Stierle moved to Butte in 1980 to teach at Montana Tech. They watched as the pit filled up with water and became an odd object of fascination. It is at once a Superfund site—a site so polluted it qualifies for federal cleanup money—and a tourist destination ($2 admission to the viewing stand). Eventually, the pit became the Stierles’ research site, too. It got started when another chemist picked up a stick in the pit covered in slime—algae. In other words, the lake was wasn’t just a toxic cesspool. It contained life—and that meant it could contain microbes that make useful compounds.

The Stierles look for drugs in unlikely places. In the early 1990s, they isolated taxol from the bark of Pacific yew trees, and the substance ended up becoming a successful treatment for breast cancer. Extreme environments like the Berkeley Pit are good places for look for unusual bacteria making unusual substances with unusual properties. At the time, though, not everyone thought it was a good idea. “They thought we were crazy because of the toxicity of the water,” says Andrea.

Going down to the toxic pit water required 40 hours of training. So the Stierles asked the Montana Bureau of Mines and Geology to do the actual collection. They got their first big sample of pit water in 1996, just after the first flock of geese had come and died.

The Stierles ended up finding hundreds of compounds from microbes in the pit water, many of them with antiviral or anticancer properties. And there was one yeast—one that Andrea described as “thick, gooey, black organism” that was very good at a totally different task, gobbling up metals from the metal-laden pit water. It’s impossible to know for sure exactly where this yeast came from, but the Stierles learned that this water-filtering yeast had only ever been found before in one particular place: the rectums of geese. The Stierles just happened to start studying the Berkeley Pit water after the 1995 geese die-off—but the timing was likely quite fortuitous.

The massive number of dead geese this year will impact the ecology of the pit too. Their bodies, to be clinical about it, are a massive infusion of nutrients. The microbes already living there could have a feeding frenzy and get a temporary population boost. “And the geese themselves are going to carry their own fungi and bacteria,” Andrea says. But she won’t get to know for sure this time.

That’s because access to the Berkeley Pit water has become restricted in the past few years. This used to be a mine, so the sides of the pit are unstable and have gotten more so. It now causes occasional landslides.“When you have one of the landslides occur, you get a kind of wave action that goes across the lake,” says Ted Duaime, a hydrogeologist with the Montana Bureau of Mines and Geology. The bureau has collected water for scientists into the past, sending hundreds of gallons around the country and as far as Japan, Australia, and Israel. That’s on hold now, but Duaime says they’re working on ways of remotely sampling the pit water, like using a drone boat.

Andrea, who is now at the University of Montana along with Don, has enough microbes in the old samples from 1996 and a later 2003 collection to keep her and her husband quite busy in the meantime. (She was, in fact, horrified to learn that a speaker at a conference cited their work as justification for not cleaning up the pit. “I wrote them a note and thanked them for their concern for our longevity as researchers,” she says, “But we got our water samples 10 years ago.”)

For now, the pit is here to stay and the Stierles are still isolating compounds from the pit’s microbes. If tectonic processes hadn’t left Montana so rich in copper and if the invention of electricity hadn’t made the metal so valuable, there wouldn't be a toxic pit in Butte now, and those geese would still be alive. But from the killer lake, the Stierles may find substances that save lives.

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