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Earliest fossilised forest discovered in Somerset
The world’s oldest known fossil forest has been discovered in cliffs along the coast of southwest England.
This extraordinary discovery gives scientists an insight into how trees shaped life on land during the Middle Devonian almost 400 million years ago.
Traces of an ancient forest found in Somerset reveal what the world was like when plant life first began to dominate the landscape.
Found in high sandstone cliffs near Minehead, the 390-million-year-old fossils are the world’s oldest known fossilised forest and the earliest fossil trees ever discovered in Britain.
The fossilised forest is made up of Calamophyton, a species described as a ‘prototype’ of modern-day trees. Looking similar to modern tree ferns, these plants had a crown of leaves like a parasol coming out of the top of a long, narrow trunk.
In a study published in the Journal of the Geological Society, researchers from the Universities of Cambridge and Cardiff identified fossilised plants, tree logs, and traces of roots and sedimentary structures preserved in the sandstone.
Dr Paul Kenrick, an expert in plant fossils at the Natural History Museum, says, “I was surprised that these fossils were found along the coast of Devon and Somerset.”
“We’ve never had any inkling that we have a fossil forest of this age in the UK. It was also quite surprising to find it in a sequence of rocks that people generally thought didn’t contain much fossil material.”
Calamophyton trees are described as a prototype of today's trees, looking similar to modern-day tree ferns. © Peter Giesen/Chris Berry.
What was the oldest forest like?
The forest preserved in these fossils lived during the Devonian period, between 419 million and 358 million years ago.
During this time, Earth had its first significant expansion of life onto land. Plants spread beyond wetlands, forming vast inland forests with more robust, woody structures. Land animals, particularly arthropods, were well-established and had expanded to even the driest habitats.
The fossilised forest would have grown on a semi-arid plain crisscrossed by small river channels spilling from mountains to the northwest. At the time, this region wasn’t connected to the rest of England, but instead formed part of what would later become Germany and Belgium, where similar fossils have been found.
The structure of the forest would have been much simpler than modern forests, with no grass, as it hadn’t evolved yet, and no undergrowth either. Instead, the forest floor would have been covered by branches shed by Calamophyton trees as they grew, supporting the invertebrates living below.
“When I first saw pictures of the tree trunks, I immediately knew what they were, based on 30 years of studying this type of tree worldwide”, said co-author Dr Christopher Berry from Cardiff’s School of Earth and Environmental Sciences.
“It was amazing to see them so near to home. But the most revealing insight comes from seeing, for the first time, these trees in the positions where they grew. It is our first opportunity to look directly at the ecology of this earliest type of forest, to interpret the environment in which Calamophyton trees were growing, and to evaluate their impact on the sedimentary system.”
Traces of fallen tree trunks, roots and sedimentary structures were among the fossils discovered in southwest England. © Neil Davies.
How did forests change life on Earth?
During the Devonian, plants evolved from small, simple structures standing just a few centimetres tall to trees towering up to 30 metres above the ground. By the end of this period, forests had developed a recognisable tree canopy and understory layer.
As plants began to spread on land, they evolved structures to adapt to this new environment. They developed stronger tissues to carry water and nutrients up longer stems, while competition for light powered the growth and expansion of these forests.
Today, plants conquer the surface of the planet. The total biomass of Earth equates to around 550 gigatons of carbon, of which over 80% is made up of plants. The evolution of trees and forests fundamentally changed the face of Earth forever.
Forests changed the landscape by weathering rocks, creating more complex habitats with deeper and more nutrient-dense soils. As debris collected under the trees, herbivores and detritivores became more common as new interactions evolved.
Trees also affected the shape of rivers and coastlines. Their root systems helped to stabilise sediment, while the build up of woody debris altered how rivers flowed across the terrain.
As well as changing the landscape, forests dramatically altered Earth’s climate, bringing regional shifts in temperature and precipitation.
“When plants evolved, they absorbed carbon dioxide from the atmosphere and locked it up in the stems, roots and leaves. Some of that gets incorporated into sediments to form coal,” says Paul.
“It’s really interesting to look at the effects of the development of forest ecosystems on Earth’s climate and the carbon cycle through the biosphere. As carbon dioxide is pulled out of the atmosphere, it causes climate cooling, and then glaciation forms in the Carboniferous Period that follows the Devonian. Forests had this massive effect of drawing carbon dioxide down and pushing oxygen levels up, which was an important driver in the evolution of animals.”
