Friday, May 13, 2005
Mount St.Helens, a source of life and wilderness
This is a wonderful picture of the volcanic eruption of Mount St.Helen.
Virginia Dale was in the first helicopter load of ecologists to land at Mount St. Helens after it erupted 25 years ago this month. "I just remember how bizarre it was going out into that landscape," she says of the suddenly gray, ash-covered terrain. "It gave the impression of total lifelessness."
Dale, at the Oak Ridge National Laboratory in Tennessee, studies ecological succession, or how an environment recovers after a major disturbance. She jokingly calls herself a "disturbed ecologist."
When it comes to studying devastation, she tells Smithsonian magazine, "Mount St. Helens was off the scale."
The eruption on May 18, 1980, blew away the top 1,314 feet of the mountain, reducing the once symmetrical, glacier-covered summit to a horseshoe-shaped crater. All told, the eruption blasted more than 230 square miles of forests, lakes, meadows and streams. It killed 57 people -- the deadliest eruption in U.S. history -- and millions of animals and plants.
Today, life has returned with a vengeance. Where the avalanche obliterated everything, Dale has counted more than 150 species of wildflowers, shrubs and trees, with an average of 10 new plant species gaining a foothold every year. It seems life can take hold even in the most desolate landscape, and in ways no scientist could have foreseen.
Life returns to Pumice Plain
Charlie Crisafulli, a U.S. Forest Service ecologist, has been watching life return to the Pumice Plain, a six-square-mile area that was buried in ash and practically sterilized by the pyroclastic flows. Today, the mossy rain-fed ground cover glows chartreuse in the low light. Dense thickets of alders and willows, many 10 to 15 feet tall, grow along new streams that flow across the plain. Frogs croak, birds call. A small herd of elk grazes in the distance. Wildflowers dot the landscape with splashes of red, yellow, pink, white and purple.
In June 1982, Crisafulli and another ecologist, surveying the Pumice Plain by helicopter, spotted the first plant they'd seen for miles. They landed and found a flowering lupine, surrounded by a ring of seedlings. The deep ash and pumice held few nutrients, but lupines, like other plants in the pea family, get nitrogen from bacteria that live on their roots. Crisafulli established a 200-square-yard study plot around that pioneering plant. Within four years, he counted 16,000 lupines in the plot; three years later, 35,000.
The flourishing of life on the Pumice Plain may have begun with that lone lupine. Once the plants enriched the soil with nitrogen, adding organic material to it when they died, other plants and then animals soon followed. Within a decade of the eruption, Crisafulli had documented more than 27 plant species in the study plot. A large patch of strawberries sprang up just outside it, probably from a single seed deposited in bird or mammal feces.
Small mammals play a part
Crisafulli has trapped 11 species of small mammals on the Pumice Plain, including ground squirrels, mice and shrews. Each has sped up the area's recovery by caching seeds, burrowing through soil and luring predators such as raptors and weasels.
The great eruption had some other surprising effects on the balance of life in the rest of the region. Amphibians also are abundant here because they happened to be hibernating underground when the volcano exploded in 1980. By the time the animals emerged a month or so later, the eruption had blasted down all the trees around the lake. More sunlight hit the water, making it unusually warm and especially rich in the aquatic organisms toads feed on. The blast also killed off most of the toads' predators. Intriguingly, the western toad is declining in most of its range beyond Mount St. Helens.
Survivors bring in more life
Toads here, shrews there -- the scattering of volcano survivors and opportunists suggests that the return of life occurs simultaneously in thousands of places at once, says Jerry Franklin, an ecologist at the University of Washington in Seattle. The lesson applies to other damaged ecosystems, he says. Loggers shouldn't clear-cut the land, for instance, but instead leave behind "lifeboats" such as snags and living trees that will sustain other organisms and foster recovery.
Mount St. Helens' recovery has had many setbacks since the 1980 eruption. Stream erosion washed away some of the research plots. Landslides buried emerging forests. And other eruptions unleashed devastating pyroclastic flows. Last fall, Mount St. Helens erupted for the first time since 1986, sending up a cloud of steam and ash.
The rumblings have continued unabated, but Crisafulli and Dale don't mind. They welcome disturbances.