In 1980, Mount St. Helen, in southwest Washington State, erupted, killing 57 people. Three years later, scientists brought two pocket gophers into an enclosed space on the northern side of the mountain. These two pocket gophers were not happy being moved from their home of Butte Camp to the northern side of the mountain. After their helicopter trip, the two grumpy gophers were released to do what they wanted to do, which, for gophers, is digging. After one day of the grumpy gophers’ digging, the places where the gophers had dug exploded with new life.

The scientists hypothesised that the gophers would turn over the soil and bring useful microbes and nutrients to the surface, where the plants could reach them. Indeed, the gopher experiment was successful because the gophers brought mycorrhizal fungus to the surface of the soil. “With the exemption of a few weeds, there is no way most plant roots are efficient enough to get all the nutrients and water they need by themselves,” says Michael Allen, a microbiologist at the University of California, who worked on the study in 1983 and the 2024 update. “The fungi transport these things to the plant and get carbon they need for their own growth in exchange.” This type of fungus also protects plants from viruses.

In 1989, the team were shocked to see 40,000 new plants in the areas where the gophers had dug, while the areas where the gophers didn’t dig remained barren. They also saw that the old-growth forests recovered much better than clear cut forests. Before the eruption, the old-growth forest had their own mycorrhizal fungi that picked up nutrients from needles on the ground. The ash from the eruption was so deep that the fungi was buried, but the gophers brought the fungus back to the surface, where the fungi could access the needles and then helped the trees grow. “In the 1980s, we were just testing the reaction,” says Allen, “Who would have predicted you could toss a gopher in for one day and see a residual effect 40 years later?”

How did two grumpy gophers replenish that enclosed space in just a day? It’s very similar to the role bilbies in Australia play in their ecosystem. When bilbies and gophers dig, they turn over soil, bringing deep layers of soil and nutrients to the surface. Plants can now access these nutrients, which allows them to germinate.