Ancient lichens paved the way for Earth’s first forests

Life on land did not begin with trees. A fossil from southern Brazil shows that lichens were already widespread about 410 million years ago, long before complex forests took hold.

A new study identifies the Devonian organism Spongiophyton as a true lichen – a living partnership between fungus and alga.

The team mapped internal filaments and cells in three dimensions and found chemical fingerprints that match those of modern lichens.

Tracing Earth’s first land builders

Inside the flattened thallus are branching hyphae, thin fungal filaments that weave through the body of the organism. Clusters of round algal cells sit alongside them, and the pattern looks like the classic fungus-alga layout seen in lichens today.

The fossil’s organic matter is rich in nitrogen and amine groups, consistent with chitin, a tough nitrogen bearing polymer in fungal cell walls. The authors also report calcite particles replacing earlier calcium oxalate, a common mineral product in living lichens.

The work was led by paleobiologist Bruno Becker-Kerber at Harvard University. His research focuses on early life on land and the deep history of lichenized fungi.

“Our findings show that lichens were not marginal organisms, but key pioneers in the transformation of Earth’s surface,” said Becker-Kerber.

The power of early lichens

Lichens help rock crumble and make the first thin layers of soil. They trap dust, unlock nutrients, and build a base that roots can later use.

Global analysis estimates that cryptogamic covers, carpets of lichens, mosses, algae on bare surfaces, fix roughly seven percent of terrestrial plant production. That slice sounds small, but it can tip local environments toward stability and growth.

These fossils sit at a pivotal moment in terrestrialization, the shift of life from water to land. They show that stress-tolerant communities were already engineering landscapes before tall plants arrived.

Uncovering the lichen connection

Spongiophyton is preserved like a mummified film, with organic matter intact and minute structures visible.

The researchers used synchrotron, a high energy X-ray source used for imaging at ultrafine scales, scans to peer inside the fossil without destroying it.

The experts observed calcite crystals forming layers near the outer surface and along filament walls.

This kind of biomineralization – organisms building minerals within their tissues – is widespread in living lichens and often starts as calcium oxalate that later alters to calcite.

Chemical tests told a second story. Abundant nitrogen compounds and alkyl-pyridines, small nitrogen-containing molecules that form when chitin breaks down – point to chitin-rich fungal tissue which is a signature unlike typical plant or free-living algal material.

Lichens before the forests

Spongiophyton occurs across multiple Devonian rock layers and sites. That spread suggests lichens were ecologically prominent just before complex forests expanded.

The fossils likely thrived in the cold, high-latitude parts of Gondwana, today’s South America and Africa. That origin fits the hardy nature of lichen communities in harsh settings.

The anatomy does not cleanly match major modern fungal groups. That gap hints at early branches of lichenized fungi that left no direct descendants.

Evidence from internal pores and surface layers also suggests gas exchange features that echo structures in some living groups. Those parallels strengthen the case that this was a lichen, not an alga or simple plant.

Lichens still shaping Earth

Lichens today still perform many of the same tasks their Devonian ancestors did. They colonize bare rock, release acids that help form soil, and anchor microscopic ecosystems in places where few other organisms can survive.

On mountainsides, deserts, and polar plains, lichens are still quiet builders of habitability. Researchers studying Earth’s early climate point out that these simple partnerships continue to shape carbon cycles on a global scale. 

By capturing and storing carbon in their tissues and the soil beneath them, lichens act as subtle climate regulators, linking the story of life’s beginnings to the planet’s ongoing balance.

Lessons from Earth’s first builders

Early land was patchy and raw, with rock, dust, and shallow soils. Lichen mats would have stabilized surfaces, slowed erosion, and supplied organic matter to build thicker soils.

They also would have affected carbon and nutrient cycling in ways that rippled outward. Even today, cryptogamic covers, thin communities that live without seeds or flowers, are major players in carbon and nitrogen budgets.

Future work can test other enigmatic fossils with the same toolkit. If more pre-forest lichens turn up, models of Devonian climate and weathering will need an update.

For now, this fossil partnership gives credit where it is due. Before roots ran deep, lichens were already doing the quiet work that made land livable.

The study is published in the journal Science Advances.

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