Mount St. Helens Attests to Nature's Resilience
Twenty-four years of ecological recovery after the eruption, ecologists find lessons for other areas subject to large disturbances
When Mount St. Helens erupted May 18, 1980, it set off an enormous avalanche, downed 3.2-million- board-feet of timber, and spewed out 400 million tons of volcanic ash, creating an ecological disturbance of vast proportions. Former Earthwatch-supported ecologist Dr. Virginia Dale (Oak Ridge National Laboratory) is using this once-in-a-lifetime opportunity to discover how ecosystems respond to disturbances on this scale.
Dale presented her findings at the Ecological Society of American meeting in Portland, Oregon, on August 6, 2004, in a symposium she co-organized on Mount St. Helens' ecological recovery. In a paper titled "Is succession successful? Synthesis and management implications of ecological recovery at Mount St. Helens," Dale and her co-authors observe how survival and succession contribute to nature's resiliency.
"The most significant finding was that ecological systems are so resilient," said Dale, former principal investigator of Earthwatch's The Recovery of Mount St. Helens project. "In some parts of the devastation zone at Mount St. Helens, organisms survived. Even where there was no survival, by 24 years post-eruption, the plants and animals are returning and community interactions are being reestablished."
Based on more than two decades of data, Dale's paper provided an overview of survival, colonization, and community development among six disturbance zones created by the eruption generated: the lava dome, debris avalanche deposit, mudflows, blown-down trees, scorched vegetation, and ash deposition. Dale used these different levels of disturbances to test various hypotheses about how succession occurs after a disturbance, and what factors influence patterns of reestablishment.
Many findings were surprising. For example, soil moisture accumulated both in depressions and on spider webs was important in trapping seeds and providing optimal conditions for seed germination. Other physical and biological legacies, chance events, life history characteristics of survivors and early colonists, and secondary disturbances all played a role in ecological recovery.
Two years after Mount St. Helens erupted, Earthwatch teams joined Dale in monitoring life's renewal on a littered and muddied blowdown debris avalanche of the "Red Zone." They helped her set up permanent sampling plots and collect information on the initial plant reestablishment. Dale and colleagues have continued this work for 24 years of data on plant reestablishment, in the process changing how ecologists think of disturbances.
"Ecologists are more and more recognizing the importance of large infrequent disturbances and considering them one of the forces shaping many ecological systems," said Dale. "Managers need to plan and prepare for large disturbances. However in the aftermath of a disturbance, managers do not always need to spend a lot of money to ‘repair' a system. The resilience of nature often means that the system will reestablish without, or in spite of, human efforts."
Dale is also in the process of co-editing a book on the subject, Ecological Recovery after the 1980 Eruption of Mount St. Helens, to be published in 2005 by Springer-Verlag.
Earthwatch Institute is an international nonprofit organization which supports scientific field research worldwide by offering members of the public unique opportunities to work alongside leading field scientists and researchers. The Institute's mission is to engage people worldwide in scientific field research and education to promote the understanding and action necessary for a sustainable environment.
For abstracts from the symposium, "Ecological Recovery After the 1980 Eruptions of Mount St. Helens," at the recent Ecological Society of American annual meeting, go to http://abstracts.co.allenpress.com/pweb/esa2004/category/?ID=32231