Mount St. Helens: How Pocket Gophers Revived Soil After a Volcanic Eruption

After a volcanic eruption left behind a barren wasteland, researchers introduced tiny “construction workers” into the soil - and an extraordinary transformation began.

In the early 1980s, Mount St. Helens in Washington State, USA, appeared to have been stripped of all life. There was grey ash, porous pumice, no shade and barely a leaf in sight. Scientists then tried a small, seemingly modest experiment involving burrowing rodents, setting off an ecological chain reaction that continues to shape the area today.

A volcano creates a dead zone

When Mount St. Helens erupted in May 1980, it tore away forests and covered the landscape with a deep layer of sterile debris. What had once been dense woodland became a bleak expanse where only a small number of plant species attempted to establish themselves.

The soils were considered “dead”: they contained almost no nutrients, experienced severe temperature swings and included porous pumice layers through which water drained rapidly. Biologists recorded only a handful of plants - just a dozen individuals. Although ecosystems have a natural capacity to recover, regeneration began at a painfully slow pace.

Researchers asked whether waiting for the wind to deliver seeds would be enough, or whether the soil itself first needed to be “brought back to life”.

The gamble on unassuming burrowers

In 1983, a research team chose an unconventional route. Rather than applying fertiliser or planting seedlings, they turned to animals regarded as pests in many agricultural areas: pocket gophers.

These small rodents spend most of their lives underground. By excavating tunnel networks, pushing mounds of earth to the surface and mixing the soil layers in the process, they alter the ground extensively. This was precisely the mechanism the researchers wanted to use.

The idea: the animals would bring older, more nutrient-rich soil up from deeper layers - together with invisible micro-organisms that had survived there.

Pocket gophers were deliberately introduced to selected test plots, while neighbouring plots were left untouched. Initially, the scene was far from dramatic: bare ground, a few plants and a great deal of rock.

Mount St. Helens: from almost empty to 40,000 plants

Just six years later, the scale of the intervention had become clear. On plots inhabited by the burrowing animals, researchers counted more than 40,000 plants. Where there had previously been scarcely a dozen individuals, a mosaic of herbs, grasses and young shrubs was now flourishing.

The adjacent control plots presented an entirely different picture: they remained largely bare, with vegetation appearing only sporadically. The contrast was so pronounced that even those involved in the project were surprised.

• Before the experiment: approximately 10–15 individual plants across the entire area
• Six years later with rodents: more than 40,000 plants on the treated plots
• Without rodents: extensive barren, open ash fields

The pocket gophers had therefore done more than dig holes. They had created the basis for an entirely new soil ecosystem.

The real stars: bacteria and fungal networks

Researchers found abundant bacteria and mycorrhizal fungi in the churned-up earth. These fungi form a living partnership with plant roots, supplying them with nutrients and water. In return, they receive sugars produced by plants through photosynthesis.

Without these underground networks, most plants would have had little chance of surviving in the sterile volcanic substrate.

Mycorrhizal threads spread through the soil like a fine internet and can even link separate plants to one another. They help make phosphorus, nitrogen and trace elements available, while also accessing water in distant pores within the rock.

One researcher involved in the work reported that trees returned remarkably quickly in some areas. Needles and dead plant material were broken down by fungi and bacteria, recycled and converted into new biomass. The ground that had appeared lifeless became a productive recycling system.

More than 40 years later: the effect remains

The most remarkable finding emerged decades afterwards. Studies carried out more than 40 years after the original intervention reached a clear conclusion: the plots containing rodents are still significantly more alive than neighbouring areas.

The microbial communities established at the time continue to function, feeding plant roots, keeping nutrients in circulation and stabilising the soil. A short-term experiment created a lasting ecological foundation.

While adjoining cleared areas still look strikingly empty, the plots treated in the past now support layered vegetation.

This type of long-term effect is unusual in ecology. Measures often lose their impact once funding ends or people stop actively intervening. Here, however, a different pattern is visible: once initiated, the soil ecosystem is largely self-sustaining - provided it is not destroyed again.

What restoration can learn from the experiment

The Mount St. Helens case offers important guidance for damaged landscapes around the world, from open-cast mining sites and fire-damaged land to areas affected by volcanic eruptions. Anyone seeking to restore such ground should focus not only on visible plants, but also on the unseen partners beneath the surface.

Several key lessons can be drawn from the experiment:

• Soil life first: Without microbes and fungi, soils remain inhospitable for a long time, even where seeds are present.
• Animals as ecosystem engineers: Burrowing species can mobilise nutrients and micro-organisms through their activity.
• Small interventions, major effects: A comparatively brief experiment triggered processes that are still having an impact today.
• Think in long timeframes: Ecological measures should be assessed over decades rather than months.

Why barren soils are so difficult to restart

Sterile volcanic ground or spoil heaps face several problems at once: they lack organic matter, humus and stable crumb structures. Water either drains away rapidly or evaporates from the surface. Nutrients are often present in forms that plants struggle to use.

In addition, without a protective vegetation cover, soils become very hot during the day and cool dramatically at night. These stress factors kill many seedlings before they can take root. A stable plant community can develop only once a minimum level of soil life has been established.

Mycorrhizal fungi are regarded as a form of nature’s “start-up funding” in this context. They extend plant root systems, reduce drought stress and may even bind certain pollutants. Many tree species have virtually no chance in extreme environments without them.

What this means for cities, farming and forestry

These findings are not limited to dramatic volcanic landscapes. Urban soils also suffer from compaction, sealing and nutrient poverty. Across intensive agriculture, soil life declines in many places where land is ploughed too heavily and fertilised too uniformly.

The same mechanisms can guide efforts to create species-rich flowering areas, regenerate forests after storms or restore degraded farmland. Useful measures include:

• using plants that work well with mycorrhizal fungi
• reducing soil cultivation so fungal networks are not repeatedly torn apart
• introducing soil from intact ecosystems into damaged areas as small “starter islands”
• supporting soil-dwelling animals that help mix the ground

Risks, limits and unanswered questions

Despite the impressive results, the experiment cannot simply be copied everywhere. Deliberately releasing animal species can be risky, particularly where they are not native or may spread uncontrollably.

Specialists therefore debate whether greater emphasis should be placed on targeted soil and microbial transfers - for example, introducing small amounts of living forest soil into damaged sites rather than establishing whole animal populations. Careful ecological assessments are needed to prevent unintended side effects.

It also remains unclear how long such microbial communities will stay stable as the climate and rainfall patterns continue to change. Heatwaves, drought and extreme weather place soil organisms under intense pressure. This is exactly why attention is increasingly turning to the question of how resilient soil ecosystems can be built.

Invisible helpers, major impact

Mount St. Helens demonstrates one point above all: a landscape’s fate is not decided solely at the surface. The crucial role is played by bacteria, fungi and small soil-dwelling creatures that are barely visible to anyone.

A few inconspicuous rodents did not merely dig tunnels after a volcanic eruption; they cleared the way for an entire plant world to return.

Anyone discussing climate protection, forest conversion or ecological restoration today cannot overlook these underground alliances. They hold enormous potential to bring damaged land back to life - if they are taken seriously and strengthened deliberately.