Thirty-five years of ecological change after the 1980 eruption of Mount St. Helens

Background/Question/Methods

The eruption of Mount St. Helens on May 18, 1980, involved diverse geological processes that disturbed forests, meadows, lakes, and rivers. Although this intense natural event caused loss of substantial life and property, it also created a unique opportunity to examine a huge disturbance of natural systems and their subsequent responses. The first team of ecologists entered the devastation within a few days of the eruption and were amazed at the transformation. Shortly thereafter these ecologists established a system of permanent sampling plots over key types of disturbances, many of which remain to this date. The plots have been the basis of recording changes in vegetation patterns and processes. Studies of animal reestablishment complimented the plant research and have focused on diverse taxa over time. The prime question being addressed by these studies is how can 35-years of study of reestablishment and recovery inform understanding of ecosystem disturbances and succession and what information is pertinent to understanding and managing land-use practices.  

Results/Conclusions

Much has been learned from the reestablishment and successional processes occurring at Mount St. Helens. First, survival of organisms was strongly influenced by characteristics of disturbance processes, timing of the eruption, local site conditions, and biological factors.  Second, ecological succession has been very complex, proceeding at varying paces, on diverse paths, and with periodic setbacks by secondary disturbance processes.  Consequently, no single, overarching succession theory provides adequate framework to explain change. Finally, human activities have greatly altered natural ecological processes in many areas affected by the eruption.  Lessons learned have rewritten scientists’ understanding of recovery and succession and have been used to restore landscapes destroyed by mining and hurricanes. For example, expecting recovery to occur from the margins, scientists were surprised to discover the importance of thousands upon thousands of surviving organisms within much of the volcanic landscape. Without plants and animals surviving in patches and in surrounding areas, recovery would not have occurred as quickly and widespread as it did.   The future pace of ecological changes at Mount St. Helens will be determined by complex processes of ecological succession influenced by landscape position, topography, climate, and further biotic, human, and geophysical forces.  This 35-year study also made too clear some of the challenges of long-term ecological studies such as ongoing disturbances, loss of permanent plots, difficulty of securing funding, and changes in taxonomy and technology (there was no GIS or GPS when we began).