The May 18, 1980, eruption of Mount St. Helens destroyed 230-square miles of forest, but it taught scientists lessons about how to heal forests walloped by natural and man-made disasters.
Scientists learned that fallen trees, stumps and other "biological legacies" of past forests provide habitat for species and help jump start recovery from disturbances. This discovery lead to the founding of "New Forestry," which encourages land managers to leave woody debris, snags and standing trees when land is logged.
Jerry Franklin, a University of Washington forestry professor, pioneered new forestry, a concept eventually incorporated into logging practices in Washington and Oregon.
Without St. Helens, loggers and foresters might have been slower to develop the concept, Franklin said.
"We may have been slow to come to developing our approach ... and we wouldn't have had the example of Mount St. Helens that made this so clear to everybody," said Franklin, 74.
Scientists knew vegetation would eventually return to the ash-covered landscape, but no one knew how long or the order in which species would return, said St. Helens Monument Scientist Peter Frenzen.
Frenzen, 52, remembers that research plots, each measuring 50 meters square, were often devoid of vegetation the summer immediately after the blast. The land was so barren, he remembers that scientists nearly celebrated finding a single alfalfa sprout laying on the ground - though they later determined the sprout must have fallen from someone's sandwich.
"That is the level of detail were looking at," Frenzen emphasized.
Plants eventually poked up from a variety of sources: Some were rooted in native soil and pushed out through as much as three-feet of ash. Others grew from seeds blown in or dropped in through bird and animal scat, he said. Many small trees survived the blast because they were protected by snow when the mountain blew.
Ash played an interesting role in tree growth. According to the U.S. Forest Service, the ash retarded tree growth for the first year following the eruption. But after rain cleared the ash from the trees, their growth recovered and, in many cases, actually increased because the ash acted like mulch, slowing the growth of competing understory vegetation and locking in moisture.
Also noteworthy was the order in which animals, insects and spiders returned to the blast zone. Ballooning spiders carried in by their silken threads by the wind were among the first creatures to return, as were beetles and ants that had colonized beneath ground during the eruption, according to the forest service. Insects and spiders provided a food source for some birds and small mammals upon their return to the blast.
Pocket gophers were another early visitor — especially those fortunate enough to be protected underground during the blast. Gophers proved to be a valuable tool for bringing healthy soil back up to the surface when they burrowed hills, Frenzen said.
Slowly but surely, most of the plant and animal species have returned to St. Helens, Frenzen said. Even beavers have wandered their way back to the area, he said.
But Frenzen said there's still much to look forward with at St. Helens. He, for one, hopes the mountain will someday house spotted owls, who only live in "dark holes of deep, dark old-growth forests."
Franklin said the recovery of St. Helens holds more discoveries for scientists as the forest grows. Despite calls for expanding recreation in the area, research opportunities need to be protected, Franklin said.
"I don't think enough people appreciate it's a place we can learn how nature does things on its own," Franklin said.