Springtail: the invisible giant

There is a “summit” that takes place every day, in every country, at any hour—even beneath our feet. In the month when World Earth Day (22 April) is celebrated, this is the hero we have chosen to honour: the springtail.

It has no agenda or spokespersons, yet its participants have been working nonstop for millions of years to keep the planet habitable. While world leaders debate how to save the soil they walk on, it is the tiny springtails that actually do so.

Every “revolution” has its activists. These ones can fit on the head of a pin, yet they have survived four mass extinctions. It was no coincidence that, in April 2020, Australian biologist Penelope Greenslade named a new Antarctic species Friesea gretae, in honour of Greta Thunberg.

An environmental hero just two millimetres long, symbol of a struggle that has lasted 410 million years. Springtails, or Collembola, are primitive hexapods related to insects, with a history that begins in the Devonian period. They have survived four mass extinctions. They inhabit soils across the globe, from the tropics to polar regions, in densities that can reach 15,000 individuals per square metre. They are probably the most numerous hexapods on Earth. And almost no one knows they exist.

Underground gardeners

Around 9,000 species are known worldwide, though scientists believe many more remain undiscovered. All this diversity converges on a common purpose: keeping soil alive and healthy.

They feed on fungi, bacteria and decomposing organic matter, returning essential nutrients to the soil that plants depend on. As they move, they disperse spores (the microscopic “seeds” of fungi and bacteria), helping them colonise new areas. By regulating what they consume, they also control populations of microorganisms that could otherwise become harmful to ecosystems.

Those who jump shake off their troubles

Springtails possess a unique ventral appendage that regulates body water with an efficiency modern engineering has yet to replicate. Some species have developed antifreeze proteins—traits that took hundreds of millions of years to evolve in other organisms.

But their most famous feature is the furcula, a forked structure folded beneath the abdomen which, when released, propels the animal in just 18 milliseconds. At a human scale, this would be equivalent to jumping over a ten-storey building. Such an efficient survival mechanism that it has inspired the development of jumping micro-robots.

A warning friend

When something disrupts the balance of the soil, springtails are among the first to respond—often before any chemical analysis detects a problem. They are environmental bioindicators: organisms whose populations directly reflect soil health.

In Portugal, a study by the Centre for Functional Ecology at the University of Coimbra demonstrated exactly this: in the Serra da Lousã, the spread of invasive acacia species silently altered springtail communities—an early sign of ecological imbalance that would go unnoticed by most assessment tools.

Having organisms that warn us before damage becomes irreversible is invaluable for agriculture, nature conservation and environmental policymaking.

Pesticides, intensive agriculture and soil degradation are among the main threats these small animals face.

Ironically, it is the same species—several floors above—that debates sustainability at international summits which poses the greatest risk to these invisible giants.

Did you know that…

• Semi-aquatic springtails, such as Isotomurus retardatus, can perform directional jumps, quickly correct their position mid-air and achieve near-perfect landings on the water surface.
• These organisms hold the record for the deepest-living terrestrial animal, having been found 1,980 metres below the entrance of a cave. They have also been recorded on Mount Everest at an altitude of 6,400 metres, making them among the highest-altitude living species.
• Springtails breathe through their skin, which is why they require moist environments to survive.
• Some springtails from the Poduridae family can emit light—continuous in some species, intermittent in others, lasting between 5 and 10 seconds.