Life › Seas, forests & the move to land › Plants colonize land
First trees & forests
c. 390–385 million years ago (England, New York)· Event· Plants & fungi
Well establishedStrong fossil, genetic or geological evidence.
The first trees and forests, appearing about 390–385 million years ago, turned landscapes of low plants into shaded woodland.
See it on the Life map →What happened
Vascular plants grew taller as they evolved wood stiffened by the tough polymer lignin. The oldest known fossil forest, about 390 million years old, was reported in 2024 from sea cliffs in Somerset, England: palm-like Calamophyton trees 2–4 m tall. Stumps of taller Wattieza trees at Gilboa, New York, are about 385 million years old. By the late Devonian, Archaeopteris, with true wood, leaves and deep roots, formed forests worldwide.
Why it matters
Forests deepened soils, drew carbon dioxide from the air, changed rivers and climate, and created new habitats on land and in streams.
The evidence (fossils, genes, rocks)
Fossil stumps and root systems at Gilboa and Cairo, New York, and in Somerset; fossil soils (paleosols) recording deep roots; and geochemical signs of falling carbon dioxide.
Still debated
How quickly forests spread, and how much their effects on soil and climate drove Devonian cooling and ocean crises.
Connections (3)
▸Vascular plants (Cooksonia) led to First trees & forestsWell established
The connection
Water-conducting tissue made height possible. Over roughly 40 million years, vascular plants added wood stiffened with lignin, leaves and deeper roots, growing from ankle-high stems to trees several meters tall. By about 390–385 million years ago they formed the first forests.
When and how
Devonian period worldwide; the earliest forests are in Somerset, England (about 390 million years ago) and Gilboa and Cairo, New York (about 386–385 million years ago).
The evidence
A clear sequence of fossils from small Silurian stems to Devonian trees in dated rock layers, including fossil stumps still standing where they grew.
Debates and open questions
Wood and tree size evolved more than once, and how different early tree groups gained height independently is still being worked out.
▸First trees & forests may have helped cause Late Devonian extinctionDebated
The connection
Deep tree roots broke up rock and built soil, releasing extra nutrients such as phosphorus that washed into the seas. That could have fed algal blooms that used up oxygen as they decayed, creating dead zones. Forests also drew down carbon dioxide, cooling the climate. Both effects line up with Late Devonian ocean crises.
When and how
Proposed by Thomas Algeo and colleagues in the 1990s; forests spread from about 390 to 360 million years ago.
How sure are we?
Uncertain: the timing broadly fits and black shales record oxygen loss, but tying forest spread to specific extinction pulses is hard.
Debates and open questions
Volcanism, cooling, ozone loss and sea-level change are rival or additional causes; how much the forests mattered is debated.
▸First trees & forests led to Carboniferous coal forestsWell established
The connection
Devonian forests established trees, wood and deep roots. In the Carboniferous, tree groups such as giant scale trees and horsetails spread across vast tropical wetlands. Their buried trunks and peat became coal on an unprecedented scale.
When and how
From Devonian forests about 385 million years ago to Carboniferous coal swamps in what is now eastern North America and Europe, about 359–299 million years ago.
The evidence
A continuous sequence of fossil plants through dated rocks, with tree types first seen in Devonian forests becoming dominant in coal seams.
Debates and open questions
Why the Carboniferous produced far more coal than other forested periods: geography, climate, or a delay in wood-rotting fungi.