‘World’s oldest forest’ sheds fascinating insight into tree evolution

20 Dec 2019

The fossilised forest. Image: Charles Ver Straeten/PA

The discovery of the world’s oldest fossilised forest in an abandoned quarry reveals how trees – very different from today’s – evolved.

Scientists have uncovered the world’s oldest forest dating back 386m years in an abandoned New York quarry, according to a new study. Fossils of a network of trees believed to be wiped out by a flood were found in the sandstone quarry in the town of Cairo, throwing new light on the evolution of trees and their role in shaping the world.

A team led by scientists from Cardiff University and Binghamton University in New York, as well as New York State Museum, has mapped out 3,000 sq metres of the forgotten forest in the foothills of the Catskill Mountains in the Hudson Valley.

It is believed to be around two or three million years older than what was previously thought to be the world’s oldest forest in Gilboa, also in New York State, some 40km away.

Trees alien to our own

The Cairo forest is believed to be older than Gilboa’s because its fossils were lower down in the sequence of rocks. The scientists say the extensive network of trees, which would have spread from New York all the way into Pennsylvania and beyond, was possibly wiped out by a flood due to the many fish fossils found on the surface of the quarry.

The forest would have included at least two types of trees – cladoxylopsids, primitive tree-fern-like plants that lacked flat green leaves, and archaeopteris, which had a conifer-like woody trunk and frond-like branches with green flattened leaves. A single example of an unidentified third type of tree was also found, which which could possibly have been a lycopod, with all the trees reproducing using spores rather than seeds.

A “spectacular” and extensive network of roots more than 11 metres in length was also found, which belonged to the archaeopteris trees. The new findings were published in the journal Current Biology.

Earth’s transition

Co-author of the study Dr Chris Berry, from Cardiff University’s School of Earth and Ocean Sciences, said: “It is surprising to see plants which were previously thought to have had mutually exclusive habitat preferences growing together on the ancient Catskill delta. This would have looked like a fairly open forest with small to moderate sized coniferous-looking trees with individual and clumped tree-fern-like plants of possibly smaller size growing between them.

“In order to really understand how trees began to draw down CO2 from the atmosphere, we need to understand the ecology and habitats of the very earliest forests, and their rooting systems.

“These remarkable findings have allowed us to move away from the generalities of the importance of large plants growing in forests, to the specifics of which plants, in which habitats, in which types of ecology were driving the processes of global change.

“We have literally been able to drill into the fossil soil between the trees and are now able to investigate geochemical changes to the soil with our colleagues at Sheffield University.

“We are really getting a handle on the transition of the Earth to a forested planet.”

– PA Media