The World’s Oldest Forest Is Here in the Hudson Valley

The discovery of fossil trees in Cairo dates the forest to approximately 386 million years old.

The original version of this story ran in January 2020. This piece was updated with additional information from our June 2024 issue.

It’s hard to step foot in the Hudson Valley without coming across some sliver of history. Tales of centuries past abound from Albany to Westchester, popping up in local museums, historic houses, and even street signs. Spanning from the age of the dinosaurs and the Revolutionary War to heyday of the Borscht Belt and the Irish Alps, the whispers of days long gone live on throughout the region.

Turns out, they live on quite a bit longer than everyone thought.

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On the floor of an abandoned quarry in Cairo, in Greene County, researchers have found the earliest tree fossils yet discovered anywhere in the world. Dating back roughly 387 million years, the find has thoroughly rewritten the story of the origins of trees. One researcher called the discovery nothing less than “mindblowing.”

In a study published in December 2019 in Current Biology, scientists discovered evidence of the oldest forest in the world right here in the Hudson Valley. Their report, which centers around a site in Cairo, is the continued effort of a research project that began in 1993. It commenced as a collaborative effort between Binghamton University’s William Stein (now retired), Cardiff University’s Dr. Christopher Berry, the New York State Museum, and the New York Paleontologists.

Working together, the group estimates the Hudson Valley forest to be approximately 387 million years old.

Oldest Forest New York
Overview of well-preserved Archaeopteris root system, left, possible Stigmarian Isoetalean lycopsid, right. Photo by William Stein and Christopher Berry

While the discovery of the forest’s age is relatively new (news broke about it in 2019), the group’s research in Cairo is not. After beginning studies in the region in 1993, the collective made significant inroads in 2007 and 2008 when they learned to recognize the bases of two types of fossil trees. According to Berry, one is the large rooting system of the Archaeopteris tree, while the other is the dish-like imprint of the Cladoxylopsid tree, which contains hundreds of radiating roots.

“These Cladoxylopsid trees had their origin a few million years earlier and are thought to be the first type of tree on the planet,“ Berry explains.

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Impressions of roots in stone indicate the existence of early trees approximately 387 million years ago.
Impressions of roots in stone indicate the existence of early trees approximately 387 million years ago.

In 2009, Charles Ver Straeten, curator of sedimentary rocks at the New York State Museum in Albany, took colleagues on a field trip to the site, which has yielded important paleobotanical research since the 1960s. There they stumbled across a network of shallow, gutter-like ditches, which he followed to a single point. Ver Straeten realized they were impressions of roots. Where they met, one of the first trees on Earth once stood.

The Hudson Valley at the time was a low-lying, swampy region occasionally inundated by a nearby sea. The largest land animals were spiders and arthropods. Most plants stood just a few feet tall. What allowed the trees at the Cairo site—a species known as Archaeopteris—to reach an unprecedented thirty feet? The answer, according to a study by Stein and Berry, is the complex root system that Ver Straeten came across that spring day 15 years ago. Roots anchored trees firmly in the soil, allowing them to absorb more water and nutrients, which enabled them to spread all over the world. “We usually think of technologies as things that Homo sapiens does,” says Ver Straeten, “but plant life also creates new technologies, new ways of doing things.”

It is no exaggeration to say that this is one of the most important things that has happened in the history of the world.

In 2010, Stein and Frank Mannolini from the New York State Museum recognized the same type of tree bases coming from the mud at the bottom of Gilboa’s Riverside Quarry, which dates to the Devonian period. They focused their research in Gilboa for a number of years, since it was widely considered the world’s first forest and contains visible tree fossils. At Cairo, on the other hand, only root impressions are still visible.

Oldest Forest New York
Overview of Archaeopteris in greenish overwash sediment. Photo by William Stein and Christopher Berry

In a later segment of the study, Stein and his team mapped around 3,000 square meters of the historic forest in Cairo. Based on an analysis of the two principal trees by Berry and Stein, they determined the forest to be close to 400 million years old.

In doing so, they also identified what the trees in question looked like. According to Berry, the Archaeopteris was a large tree with broad green leaves, a solid trunk, and a modern-seeming root system. The Cladoxylopsid, meanwhile, had branches with twiggy leaves attached to a mostly hollow trunk supported by ribbon-like roots. They both grew in soil that was seasonally dry.

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While the group’s discovery in Cairo is significant in itself, it’s even more noteworthy because it refutes the previously accepted information that the site of Gilboa, a mere 40 minutes away, was the oldest forest in the world. In fact, the Gilboa forest is a few million years younger and had soil that was permanently wet. Unlike the Cairo forest, the Gilboa one saw Cladoxylopsids as the dominant trees, with nary an Archaeopteris in sight.

Oldest Forest New York
Eospermatopteris root system in overwash sediment. Photo by William Stein

So what does the discovery mean in the context of the Hudson Valley’s natural history?

“What we are really seeing here, taking into account all the evidence, is that there were different types of forests growing in different types of environments on the Catskill Delta during this time,” Berry explains.

It is no exaggeration to say that this is one of the most important things that has happened in the history of the world. Those early trees absorbed carbon dioxide from the atmosphere, which led to a rapid cooling favorable to more complicated forms of animal life. The shade provided by the broad, flat leaves of taller trees protected critters on the ground from the sun, and the roots limited soil erosion. “The arrival of these forests was the creation of the modern world,” Berry told Smithosonian Magazine.

Eventually, the remains of those early plants and trees, compacted over hundreds of millions of years, became the coal deposits that fueled the Industrial Revolution, returning the carbon they had absorbed into the atmosphere, thereby triggering the present age of global warming.

As for the Cairo quarry, Stein—now retired—says there remains more to be discovered. Joe Hasenkopf, chairman of the town’s planning board, hopes to raise money to build a visitors’ center and research laboratory so both tourists and scholars alike can benefit from access to the exquisitely preserved site.

Related: What Did the Hudson Valley Look Like During the Age of the Dinosaurs?

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