The world’s oldest known fossil forest has been discovered in a sandstone quarry in New York state, offering new insights into how trees transformed the planet.

The forest, found in the town of Cairo, would have spanned from New York to Pennsylvania and beyond, and has been dated to about 386m years old. It is one of only three known fossil forests dating to this period and about 2-3m years older than the previously oldest known fossil forest at Gilboa, also in New York state.

“These fossil forests are extremely rare,” said Chris Berry from Cardiff University’s School of Earth and Ocean Sciences. “To really understand how trees began to draw down carbon dioxide from the atmosphere, we need to understand the ecology and habitats of the very earliest forests.”

The forest would have been quite open and its ancient trees would appear alien to the modern eye. A walker would have encountered clusters of Cladoxylopsid, a 10m-tall leafless tree with a swollen base, short branches resembling sticks of celery and shallow, ribbon-like roots. The fossils also revealed a tree called Archaeopteris, something like a pine, but instead of needles the branches and trunk were adorned with fern-like fronds, giving it an almost hairy appearance. “It’s not something we can immediately recognise as a modern tree,” said Berry.

Facebook Twitter Pinterest The emergence of forests marked permanent changes Earth’s ecology, atmospheric CO2 levels and climate. Photograph: Charles Ver Straeten/PA

Archaeopteris also featured enormous woody roots, which had not previously been seen in forests of this era.

The prehistoric forest would have been sparse on wildlife. The first dinosaurs would only appear 150m years later and there were no vertebrates on land yet and no birds. The forest’s primary occupants were millipede-like creatures, called myriapods, and some other primitive insects that may or may not have begun to fly.

“It’s funny to think of a forest without large animals. No birdsong. Just the wind in the trees,” said Berry.

The emergence of forests is one of the most transformative events in Earth’s history, marking permanent changes to ecology, atmospheric CO2 levels and climate. Before forests, CO2 levels were far higher and the Earth’s climate was hotter with no ice caps. By the end of the Devonian period, about 350m years ago, there were glaciers and, soon after, polar ice became permanent.

However, there have been so few fossil remains of early trees that scientists have had only a hazy idea of which trees dominated which habitats, how root systems altered soil chemistry and how forests opened up new ecological niches for animals.

“These remarkable findings have allowed us to move away from the generalities of the importance of large plants growing in forests,” said Berry. “We are really getting a handle on the transition of the Earth to a forested planet.”

Today, forests cover about 30% of the planet and are being cleared on a massive scale. Between 1990 and 2016, the world lost 502,000 square miles of forest, according to the World Bank – an area larger than South Africa – and about 17% of the Amazon rainforest has been cleared over the past 50 years. Even without accounting for the impact of burning fossil fuels, deforestation could lead to profound changes to the world’s ecosystem and climate. “If you reverse that process [of forestation] you probably lose the ice,” said Berry.