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From Mt. St. Helens’ volcanic ashes, Mother Nature rebuilds

May 18, 2016 at 6:20 PM EDT
Wednesday marks the 36th anniversary of the deadliest volcanic event in U.S. history: the eruption of Mount St. Helens, which killed every living thing in a 230 mile radius. But the slopes around the volcano are now beginning to repopulate with plant and animal life, giving biologists a unique opportunity to watch an ecosystem develop in real time. Science correspondent Miles O’Brien reports.
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JUDY WOODRUFF: Mount St. Helens in Washington state is one of the most well-monitored volcanoes on the planet, and with good reason. It’s still active.

And more than three decades to the day after it launched a stunning and destructive display of lava and ash, it continues to transform a region and its ecology. Even now, scientists are still learning about the aftermath, and how some life is emerging from the ashes.

Science correspondent Miles O’Brien has the story, part of our new weekly series about exploring the Leading Edge of science.

MILES O’BRIEN: Thirty-six years after its spectacular, deadly eruption, Mount St. Helens still rumbles and bears scars from that earth-shattering day.

But hike down the slopes, away from that jagged crater just a little, and you will see Mother Nature hard at work. And there’s a good chance you will bump into a team of scientists led by John Bishop. He is an evolutionary biologist at Washington State University-Vancouver.

JOHN BISHOP, Washington State University-Vancouver: The goal of our research is to understand how plant and animal communities reform after a catastrophic disturbance.

MILES O’BRIEN: Bishop is one of a select group of researchers studying this rebound from a volcanic eruption. Back in 1980, Mount St. Helens had given scientists all kinds of clues that a big disturbance was brewing.

Two months before it blew, the volcano was venting huge amounts of steam and there was a series of earthquakes. Even with all those ominous signs, the eruption was larger than anyone predicted. It happened at 8:32 on the morning of May 18, 1980. An earthquake caused the north face of the mountain to collapse.

JOHN BISHOP: After that, it uncorked an explosion that was directed horizontally, and leveled the forest to 13 miles out from the volcano.

MILES O’BRIEN: The eruption column of volcanic ash and gas rose 80,000 feet, while a tsunami of 1,800-degree gas and rock raced down the valley at 450 miles an hour, a so-called pyroclastic flow.

JOHN BISHOP: Anything biological that was remaining after the landslide would’ve been completely vaporized. It was just a barren landscape, gray and pumice-colored.

MILES O’BRIEN: It killed every living thing in a 230-square-mile area. What was left was akin to a moonscape; 57 people died. Some remains were never recovered.

Bishop and his team have had a front-row seat as nature got busy bringing this place back to life. They wanted to know where it begins and how it takes root. Here, it started with these purple flowers. Alpine lupine were the first plants to return. For many years, they were pretty much the only game in town. But as they went through their life cycles over several seasons, they created soil from the volcanic ash.

And that made it possible for woody plants, like the Sitka willow, to find a home. They are how a forest gets started, but it hasn’t been easy for them.

JOHN BISHOP: One of the things we have realized about these willows is that they’re not getting big. That’s important, because they create habitat for birds and mammals. We have learned that these landscapes are characterized by extreme instability in the populations of the plants and animals that colonize them.

MILES O’BRIEN: In a recovering ecosystem like this one, where just a few species have managed to regain a toehold, even seemingly insignificant pests can play an outsized role in how the landscape bounces back. These weevils are an invasive species with a particular taste for the Sitka willow.

JOHN BISHOP: Any stem larger than about one centimeter is usually destroyed by this weevil, and the effect of it is to keep these plants small, not let them form the architecture that’s needed for bird and mammal habitat.

MILES O’BRIEN: But Bishop says it’s important to remember we are still early on in what will be a very long game. He says the plants and insects will battle it out over time, and eventually the ecosystem will become more diverse, more stable, and this will be a forest again.

JOHN BISHOP: When I’m out there working on the pumice plain, you know, one moment, I will look around, and I will be stunned by the amount of vegetation and the number of birds that are present. But then, the next moment, I step back and I think, there is hardly anything here.

We’re centuries away from replacing the old-growth forest that was there.

MILES O’BRIEN: Mount St. Helens is the perfect place to test an important question in ecology. Life does go on, but how? John Bishop will keep looking for the answer here, unless Mount St. Helens awakens and reboots the landscape once again.

Miles O’Brien, the “PBS NewsHour.”

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