Mount St. Helens Revisited
DB: This is Earth and Sky. On May 18, 1980, the top blew off Mount St. Helens in Washington state.
JB: This volcanic eruption leveled hundreds of square kilometers of forests. But pockets of life survived—and provided footholds for recolonization. Imagine a sparrow flying across a barren landscape. It spots an isolated, upside–down tree with dead roots hanging in the air. While the bird rests on the moist, decaying matter, it drops a grass seed—and recovery begins.
DB: Scientists have learned that where any structure at all survived around Mount St. Helens, life came back more quickly. Now what were forest landscapes are largely meadowlands with grasses, insects, birds, gophers, mice—and even some shrubs and trees. This disproves traditional models that say recolonization always occurs in a strict sequence—from mosses to lichens to herbs to shrubs and, finally, to trees.
JB: Mount St. Helens has helped ecologists understand the recovery process following large–scale natural disturbances. It’s also providing insight into recovery from human disturbances such as strip–mining and clear–cutting. This much seems clear—recolonization goes faster when even minimal biological legacies are left standing. Special thanks to the U.S. Forest Service—caring for your national forests and grasslands. We’re Block and Byrd for Earth and Sky.
Our thanks to the following individuals and institutions who assisted in the preparation of this script:
Charlie Crisafulli
Research Ecologist
US Forest Service
Pacific Northwest Research Station
Olympia, Washington
HELPFUL WEB SITES:
U.S. Geological Survey’s Cascades Volcano Observatory Site
All about Mount St. Helens (USGS)
The U.S. Forest Service’s Mount St. Helens National Volcanic Monument site (includes photos):
AUTHOR’S NOTES:
When Mount St. Helens erupted on May 18, 1980, some organisms survived, and others did not—and it’s important to recognize the role of chance in shaping that pattern of recovery. For example—in the state of Washington in mid–May, 1980—a lot of organisms were still protected beneath a layer of ice and snow. So aquatic systems such as amphibians, plankton, water insects and fish did very well in the higher elevations. If the eruption had occurred in, for example, August, the results would have been quite different.
As it turns out, very few species were altogether eliminated by the eruption. Most species have, so far, either fared much better or worse than before the blast. One that that fared better was the northern pocket gopher species, protected from the lava and ash by their underground habitats. But these gophers may not thrive as well in the 20 or 30 years after the eruption, while forest ecosystems become more thoroughly reestablished.
Mount St. Helens is now a national monument as well as a scientific observation area. In May, 2000, scientists involved in the original study reunited to compare data and findings. Through the summer of 2000 they will be conducting new measurements and mapping a long–term research strategy.
