In 1980, a magnitude 5.1 earthquake accompanied by an avalanche flipped the switch on Mount St Helens, a volcano in the western USA. With the pressure removed from the magma below, the volcano erupted, destroying 350km2 of forest and killing 57 people. But three years later, in 1983, scientists put two wild gophers in a small, fenced enclosure on the volcanic plain. They then left them to dig for 24 hours before removing them. According to a new study, those two little rodents have caused benefits to the mountain ecosystem that could still be seen decades later.
“In the 1980s, we were just testing the short-term reaction,” says study co-author Professor Michael Allen, a microbiologist at the University of California – Riverside, USA, who worked on the 1983 study and the 2024 update. “Who would have predicted you could toss a gopher in for a day and see a residual effect 40 years later?” He says.
The team had thought, in the 1980s, that gophers would help the soil recover from the lava and ash by digging through the top layer of volcanic debris and bringing helpful microbes back up to the surface. They also believed that they would fertilise and aerate the soil, and bring in microorganisms like bacteria and fungi. Six years after the gophers had been removed, the team discovered that the area where the gophers dug was flourishing with bright heathy plants, while the neighbouring landscape was still struggling to survive.
In 2014, 31 years after the gophers, the team returned and took samples of soil from the gopher holes and other areas that the gophers didn’t touch. They found very clear differences in the microbial diversity from the gopher and non-gopher spot. The scientists also found that the main way they got plants to thrive was mycorrhizal fungi. This fungi forms symbiotic relationships with plant roots, allowing them to access more nutrients from the soil and protecting them from diseases.
Interestingly, they also found a difference between the areas where forests used to grow, (old growth forests) and areas of forest that had been cut down before the volcanic eruption (clearcut areas). They found that the old-growth forests recovered much better and faster than cut down areas, which remained barren.
“There still isn’t much of anything growing in the clearcut area,” says co-author Associate Professor Emma Aronson, a microbiologist at the University of California, Riverside. She continues, “It was shocking looking at the old growth forest soil and comparing it to the dead area.”