The eruption of Mount St. Helens 30 years ago destroyed so much that often overlooked is what it created. Scientists are witnessing the assembly, species by species, of an entirely new ecosystem.
Lynda V. Mapes Seattle Times 15 May 10;
The eruption of Mount St. Helens 30 years ago destroyed so much that often overlooked is what it created: an entirely new ecosystem. More than 130 new ponds and two new lakes were birthed at the foot of the volcano. What's going on today in and around these ponds isn't restoration, or renewal, or recovery.
Salamanders, frogs and toads are not just moving back where they were before the eruption. They are taking on whole new territory.
It's the assembly, species by species, of a new habitat.
"Build it, and they will come," said Peter Frenzen, spokesman for the U.S. Forest Service here. Scientists working at the monument have found that large disturbances make large changes, which produce habitat, he said.
"Life takes that as a starting point," he said. "It's sort of a new day."
The ash and debris unleashed by the eruption impounded streams and seeps, and depressions between them held rain and groundwater. The result is a full complement of ponds. There are warm, shallow, sunny ponds, called pans, dry by summer. And kettle-like ponds that hold water well into fall.
Charlie Crisafulli, ecologist for the U.S. Forest Service Pacific Northwest Research Station, has studied change at the mountain since it blew its stack. He has a name for a deep, groundwater-fed pool as he swishes a dipnet through the 50-degree water, looking for eggs: "Red-legged frog heaven."
To be sure, the evidence of destruction is still everywhere here. Hills of volcanic material, too steep or dry for plants to grow on, remain as stark reminders of the day the mountain turned inside out.
The eruption of Mount St. Helens on May 18, 1980, was a ferocious blast. In all, 57 people died, along with an uncounted number of animals. Within three minutes, a lateral blast from the volcano, traveling at more than 300 mph, blew down and scorched 230 square miles of forest.
It was the most economically destructive volcanic eruption in U.S. history. A plume of ash billowed from the crater for nine hours, spewing gray grit more than 15 miles up into the air. Wind carried the ash eastward across the country, snowing on Yakima, Spokane and western Montana, and dimming skies enough that the streetlights turned on. Interstate 90 between Seattle and Spokane was closed for a week.
It is difficult to comprehend the scope of the destruction. A massive landslide — the largest in recorded history — plugged 24 square miles of North Fork Toutle River valley to an average depth of 15 stories. Mudflows barreled down the volcano as fast as 90 mph, so much sediment that it plugged the shipping channel in the Columbia River some 70 miles from the mountain, blocking oceangoing shipping until emergency dredging was completed.
"What is left behind, from a human perspective, probably looks pretty messy; but from a habitat perspective, it is a lifeboat, and a starting point for the species that come in," Frenzen said.
Pristine habitat created
The ecological reset button pushed by Mount St. Helens was of, well, volcanic proportions: a fivefold increase in pond habitat was created by the eruption.
From the ashes, the new community of frogs, salamanders and toads has risen, even burgeoned, in an environment pristine and new as Eden. Some populations are healthier than anywhere else in the state, without the usual amphibian woes. There is no development here. None of the killer fungus plaguing frogs elsewhere. Populations of garter snakes and other predators haven't yet returned everywhere in usual numbers, giving the frogs, toads and salamanders a temporary leg up.
Over the years since the eruption, some have been tagged and tracked, amazing scientists who learned just how far they travel to get to the ponds or other habitat within the blast zone. One salamander even scaled a 70-degree slope with a 784-foot elevation gain through a blow-down forest. Scientists believe they find the ponds by following moisture and chemical cues, but their migratory finesse isn't fully understood.
"Given a chance, life will find a way," Frenzen said. "It makes you realize what an amazing planet we live on, the power and capacity for change."
Chorus frogs, Western toads, red-legged frogs, Cascades frogs, Northwestern salamanders, and, by the 10th year, the first rough-skinned newts all made the trek to the new ponds. By now, all of the pond breeders typical of the region are present save one, the long-toed salamander, exceedingly rare here even before the eruption.
Some animals, such as the Northwestern salamander, even have played a shrewd survival hand, keeping their gills and living their entire lives as aquatic animals rather than moving onto land as they grow. That enables them to take advantage of their new pond environment, and shrug off the loss of the mature forest they normally use as adults.
An upside of the volcano's swap-out of mature forest for young alders is warm, sunny ponds replete with algae for tadpoles and aquatic salamanders to eat, stoking populations.
Eventually, trees will grow up and shade the ponds, and some shallower ponds will disappear as the trees suck up the water and fill them with leaf litter. And in a typical boom-and-bust cycle, what Crisafulli calls the three p's — predators, pathogens and parasites — will rip on the abundant amphibian feast awaiting them. Their numbers, in turn, will diminished as the frogs, toads and salamanders are knocked down.
Such cycles are at their most extreme at the early stages of a new ecosystem, such as these ponds. The swings will be less dramatic as the ecosystem becomes more mature and in balance over time.
Richness begets richness
Sometimes it's what is not yet here, as the ecosystem assembles, that is striking. For all the delicious ooze around the ponds, skunk cabbage has yet to show up here, but for a few spots. The seeds just aren't here, though the plant thrives in other similar environments.
Also missing in action so far: infestations of exotics and weeds, which have yet to dominate or take over any part of the area. Solid populations of other animals and plants have become keystones of the ecosystem. Elk roam in voracious herds, chewing down willow, paintbrush and sedges. Lupine have enriched the soil, and gophers that survived the blast underground have proved surprisingly important, pushing up nutrient-rich soil from below the ash and even providing migratory tunnels for toads.
Timing helped many animals and plants get a headstart recolonizing the area. The blast came in early spring. Ice and snow protected some plants, and some frogs and toads and salamanders were still tucked away in hibernation pits or lake-bottom sediments. Or they were snugged deep in duff, or protected by a hill, a rise or some other accident of topography.
Three decades later at the ponds, richness has begotten more richness here: beavers, drawn to alders and willows in the ponds and wetlands, are creating ponds of their own, alive with frogs, birds and waterfowl.
The result today is an ecosystem teeming with croaking, chorusing, singing, flying, swimming, chewing life.
Crisafulli pauses by a beaver dam and grand lodge impounding a pond graced with teal and the calliope music of blackbirds. "You look at that grand lodge, you hear the red-winged blackbird, you see the teal," he said. "You can't imagine all this was assembled in three decades. It's quite astonishing."
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