Earth’s first forests: trees before modern trees

Forests changed the surface of the Earth, but the earliest ones did not look like modern woodland. In the Middle Devonian, around 390 million years ago, cladoxylopsid trees formed stands with branching trunks and unusual crowns. Fossil roots, stems and the sediments around them reveal an emerging forest ecosystem before conifers and flowering plants existed.

Plants colonised land before forests

Small land plants appeared hundreds of millions of years before trees. Early forms were low-growing and lacked the tall woody trunks and deep root systems of later forests. Through the Silurian and Devonian, vascular plants developed stronger conducting tissues, branching stems and varied reproductive structures. Tree-like growth evolved in more than one plant lineage, so there was no single “first tree” that gave rise to all later forests.

The earliest forests were assemblages of different plants. Cladoxylopsids, lycopsids and progymnosperms had distinct architectures. Some had tall trunks with a crown of branches; others spread woody rhizomes or had roots that penetrated only shallow soils. The fossil record preserves pieces of these bodies in different ways, so an isolated trunk or stump can be difficult to reconstruct without its setting.

The Somerset forest and Calamophyton

Fossils in the Eifelian Hangman Sandstone of Somerset and Devon, southwest England, preserve one of the oldest known forest landscapes, dating to roughly 390 million years ago. The remains include cladoxylopsid trees assigned to Calamophyton, along with other plants and sedimentary structures created by vegetation. The strata are older than the better-known forest horizon at Gilboa, New York.

Calamophyton was not a modern palm. Its trunk carried distinctive branching systems, and the plants were shorter than many familiar forest trees. Fossil fragments and sediment relationships support reconstructions of stands, but the exact height, spacing and appearance of every individual remain uncertain. The artwork on this page is an interpretation of that plant group, not a photograph of a complete fossilised forest.

What a fossil forest records

A fossil stump is evidence of a plant; a rooted stump in place, repeated across a mapped surface, can reveal that trees grew together. At Gilboa, researchers mapped more than a thousand square metres of ancient rooting horizon and found several kinds of tree. Their arrangement and root systems revealed a wetland coastal plain, not a uniform grove of one species. Other sites preserve trunks, leaves or wood carried away from where the plants grew.

Fossil forests also record ecological neighbours. Plant debris accumulated in waterways, roots stabilised some sediments and trunks altered how water flowed during floods. Tracks and burrows can reveal animals using the same landscape. Such evidence shows interactions between vegetation and the physical environment, although it rarely identifies the exact behaviour of every animal or plant.

How trees changed landscapes

Roots bind sediment and can break down rock, while leaves and branches slow wind and water near the ground. Plant material contributes organic matter to soil and river deposits. As forests spread, these processes helped change erosion, floodplains and the movement of nutrients. The direction and strength of each effect depended on local climate, geology and the structure of the forest.

These early forests were not yet the deep-rooted, high-canopy woodlands familiar today. Later plants evolved more extensive wood, leaves and root systems. Carboniferous coal forests, with abundant lycopsids and other wetland plants, formed a later stage in forest history. Mesozoic conifers and still later flowering-plant forests added further ecological changes. It is misleading to project the structure of a modern forest backwards across all these periods.

Limits of the record

Plant fossils are unevenly preserved. Wet sediments can bury trunks and roots in place, while dry uplands may leave little evidence. The apparent first appearance of a forest therefore depends on where suitable rocks have been exposed and studied. A newly discovered site can push a date back without proving that forests began everywhere at the same time.

Devonian forest fossils document an important ecological transition: plants became tall enough to form stands and influence landforms. They do not identify a single birthplace of forests or capture every plant community. By combining fossils, roots, sedimentology and age estimates, researchers reconstruct multiple early forest types and the environments that they helped transform.