The First True Trees

c. 385 Million Years Ago · Deep-Dive Event Pages · hidden-connections

The massive plants that accidentally triggered an ice age and mass extinction.

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During the Devonian period, the first true trees (like Archaeopteris, which had fern-like leaves and woody trunks) evolved. These massive forests radically transformed the Earth's surface and atmosphere.

Key Numbers

When: ~385 million years ago (Middle-Late Devonian)
Oldest known forest: Cairo, NY — ~386 Ma
Tallest early tree: 8+ m (Wattieza/Eospermatopteris)
Archaeopteris height: up to ~30 m (100 ft)
Root spread at Cairo: Archaeopteris roots >11 m long

Verified Facts

The fossilized stumps at Gilboa, New York — known since the 1870s and named Eospermatopteris — were the world's earliest recognized forest, but for over a century no one knew what the trees above the stumps actually looked like.
In 2007, William Stein, Christopher Berry, Linda Hernick and Frank Mannolini published in Nature that the Gilboa stumps belonged to Wattieza, a cladoxylopsid that stood at least 8 meters tall — finally giving the ~385-million-year-old 'earliest trees' their crowns.
Wattieza/Eospermatopteris was not a flowering plant or conifer but an extinct cladoxylopsid, a relative of modern ferns and horsetails; instead of true leaves it bore branches that repeatedly forked into bottlebrush-like fronds and reproduced by spores, not seeds.
Archaeopteris, which spread in the Late Devonian (roughly 385-359 million years ago), is widely regarded as the first 'modern' tree: it combined a true woody trunk and conifer-like branching with flat green leaves, yet still reproduced by spores rather than seeds.
Archaeopteris and its kin (progymnosperms) owed their tree stature to a bifacial vascular cambium, the innovation that let trunks add wood (secondary xylem) and grow outward in girth as well as upward — the same mechanism modern trees use.
Archaeopteris reproduced with two spore sizes — larger megaspores producing eggs and smaller microspores producing sperm — a heterosporous condition that leads many paleobotanists to see it as closely related to the ancestry of seed plants.
In December 2019, Stein, Berry and colleagues reported in Current Biology that an abandoned quarry near Cairo, New York preserves an even older forest — about 386 million years old, some 2-3 million years older than Gilboa — making it the oldest known forest on Earth.
At Cairo the team mapped at least three distinct rooting systems sharing one ancient soil: cladoxylopsid Eospermatopteris, an enigmatic early lycopsid, and extensive Archaeopteris root networks reaching more than 11 meters in length — pushing modern Archaeopteris-type rooting back roughly 20 million years earlier than expected.
By drawing down carbon dioxide through photosynthesis and by driving deep-rooted silicate weathering of soils, the spread of these first forests is implicated in a major Devonian decline in atmospheric CO2; CO2-proxy compilations indicate a drop from on the order of ~2,000 ppm in the Early Devonian toward below ~1,000 ppm by the Late Devonian.
Researchers have linked the rise of large, deeply rooting Devonian trees to dramatic Earth-system effects, including enhanced weathering and nutrient runoff that may have fueled algal blooms and ocean anoxia — a plausible contributor to the Late Devonian marine extinctions.

The World at This Moment

The first trees arose in the Middle Devonian (Eifelian-Givetian, c. 393-383 Ma), an interval when continents were assembling toward Pangaea and Euramerica straddled the equator. The seas were dominated by stromatoporoid-tabulate coral reefs, brachiopods, trilobites, ammonoids, and armoured placoderm fish such as Dunkleosteus; the Devonian is justly called the "Age of Fishes." On land, vertebrates had not yet emerged—tetrapod transition forms like Tiktaalik (c. 375 Ma) and Acanthostega lay slightly ahead—so terrestrial ecosystems belonged to plants, arthropods, and early invertebrates. The earliest forests are documented at Gilboa and Cairo in New York and, more recently, in the Hangman Sandstone of Devon and Somerset (c. 390 Ma; Davies et al. 2024). Atmospheric CO2 remained high but was beginning a long Paleozoic decline; this same window preceded the Kellwasser (Frasnian-Famennian) and Hangenberg (end-Devonian) mass extinctions, among the "Big Five" Phanerozoic biotic crises that reshaped marine life.

The Paradigm Shift

Trees transformed Earth from a thinly vegetated planet into a forested one, restructuring the carbon, water, and sediment cycles. Wattieza (Middle Devonian, c. 385 Ma) achieved arborescent height through cladoxylopsid construction, but Archaeopteris—a progymnosperm with a bifacial vascular cambium yielding true secondary wood and the first laminate leaves—built the first canopy forests and deep root systems by the late Givetian-Frasnian. Deep, fracturing roots accelerated silicate weathering and pedogenesis, and the "Devonian plant hypothesis" (Algeo & Scheckler 1998) links this to a steep drawdown of atmospheric CO2 and global cooling across the later Paleozoic. Forests created the first stable soils, woody detritus, and complex terrestrial microhabitats, founding the modern terrestrial biosphere. They also enabled the evolution of seeds and, by sequestering carbon, helped raise atmospheric oxygen toward the Carboniferous coal-forest world. In effect, the rise of trees coupled the land surface to ocean and atmosphere chemistry for the first time at a planetary scale.

In Their Own Words

"The earliest known evidence for forests consists of fossil tree stumps, about 385 million years old, from Gilboa in upstate New York, known since the 1870s and assigned to the genus Eospermatopteris." — William E. Stein, Frank Mannolini, Linda VanAller Hernick, Ed Landing & Christopher M. Berry, "Giant cladoxylopsid trees resolve the enigma of the Earth's earliest forest stumps at Gilboa," Nature 446 (2007): 904-907 (opening of the abstract; paraphrased wording of the published abstract).

In Depth

The Tower That Rewrote the Air

Roughly 385 million years ago, in the swampy lowlands of the Middle and Late Devonian, life solved an engineering problem that the planet had never faced: how to stand up. The first true trees — the fern-leaved, conifer-like The First True Trees (sv-first-trees) pioneer Archaeopteris, alongside the palm-trunked Eospermatopteris of the famous Gilboa stumps in New York and the earlier Wattieza — were not just bigger plants. They were a new geological force wearing bark. To understand why a tree is one of history's hinge events, you have to look both backward at the deep machinery that made it possible and forward at the world it manufactured.

The preconditions: oxygen, complexity, and the move to land

A tree is the end of a very long supply chain. It needs an oxygen-rich atmosphere, a legacy of The Great Oxygenation Event (sv-great-oxygenation) and the photosynthetic bacteria that preceded it. It needs the cellular toolkit of The First Complex Cells (Eukaryotes) (sv-first-complex-cells) and the genetic reshuffling unlocked by The Invention of Sexual Reproduction (sv-invention-of-sex), which let plant lineages adapt fast enough to colonize a hostile dry world. Above all, it needs a beachhead on land — the threshold crossed when lobe-finned vertebrates like Tiktaalik & The Move to Land (sv-tiktaalik) were hauling themselves onto shores already greened by low, creeping early plants. Trees were the vertical escalation of that invasion. The decisive innovations were lignin, the rigid polymer that let stems resist gravity and grow tall toward the sun, and deep roots, which let a plant anchor itself and mine water and minerals from rock.

The ripple effects: a planet remade by roots and wood

The consequences were staggeringly out of proportion to a single organism. Those deep roots cracked bedrock and accelerated chemical weathering, pulling carbon dioxide out of the atmosphere on a scale that helped tip Earth into an icehouse climate. The forests' fallen wood, built of a molecule that early microbes could barely digest, piled up and eventually became the vast coal seams of the following Carboniferous period — the buried Devonian sunlight that, hundreds of millions of years later, would power The Industrial Revolution (sv-industrial-revolution). Trees also built soil itself, creating the three-dimensional habitat that an exploding cast of land animals would exploit: the spread of forests is bound up with The First Insects (sv-earliest-insects), whose later relatives would grow giant in the oxygen-thick Carboniferous air the forests helped produce.

This was the deepening of a revolution that began with The Cambrian Explosion (sv-cambrian-explosion) in the seas and the soft-bodied experiments of The Ediacaran Biota (sv-ediacaran-biota) before it. Where those events filled the oceans, the trees terraformed the continents — turning bare, eroding mudflats into shaded, layered, living architecture.

The long thread forward

Every later chapter of terrestrial life is staged inside the world the first trees built. The forest floor and canopy gave evolutionary room to the lineages that produced The First True Mammals (sv-first-mammals), and the arboreal life of branches selected for the grasping hands and stereoscopic vision of The First Primates (sv-first-primates) and later The Rise of the Great Apes (sv-great-apes) — our own deep ancestry is, quite literally, a story written in trees. When humans finally arrived, wood became civilization's first universal material: fuel, tools, ships, the spokes of The Invention of the Wheel (sv-wheel), the timbered halls and pyres of every culture that followed.

The first tree is a quiet entry on a timeline that runs from The Big Bang (sv-big-bang) to artificial minds, easy to overlook beside supernovas and empires. But it marks the moment life stopped merely living on the planet and began rebuilding it — drawing down the sky, laying up the coal, and raising the green scaffolding on which nearly everything human would one day be made.

Causes & Consequences

What led to it

The colonization of land by the first vascular plants in the Silurian, exemplified by the tiny dichotomously branching Cooksonia around 425-430 million years ago, established the rooted terrestrial lineage from which trees would later arise.
The evolution of lignin and lignified tracheids gave plant cell walls the rigidity to resist collapse, conduct water under tension, and support erect bodies, supplying the structural chemistry that woody trunks would depend on.
The origin of the vascular system of xylem and phloem (the hallmark of tracheophytes) created the internal plumbing needed to move water and sugars through a tall organism, a prerequisite for growing far above the ground.
The innovation of a bifacial vascular cambium, which produces secondary xylem (wood) inward and secondary phloem outward, allowed plants to thicken their stems and grow outward as well as upward, the defining feature of true trees.
The earlier Middle Devonian arborescent plant Eospermatopteris (the Cladoxylopsida preserved at the ~385-million-year-old Gilboa fossil forest in New York) created the first tree-like stands and prefigured the forest habit that Archaeopteris would perfect.
The evolution of a deep, branching, modern-style root system in Archaeopteris, comparable to that of living seed plants, let the trees anchor large bodies, mine the substrate for water and nutrients, and build deep soils.

What it set in motion

Archaeopteris spread across every continent during the Late Devonian (about 385-359 million years ago), colonizing floodplains and coastal lowlands to create Earth's first widespread forests with a shaded, multi-storied understory.
The deep roots of these trees accelerated the chemical weathering of silicate rocks and helped lock carbon into soils and sediments, driving a major drawdown of atmospheric CO2 that contributed to long-term global cooling.
Nutrients such as phosphorus released by forest-driven weathering washed into shallow seas, where many researchers argue the resulting eutrophication and ocean anoxia (recorded in black shales at the Kellwasser and Hangenberg events) helped trigger the Late Devonian mass extinctions.
Forests built the first thick, widespread topsoils and stabilized riverbanks, which transformed landscapes and is thought to have shifted rivers toward more meandering, single-channel forms across the Devonian world.
The tree habit set the stage for the Carboniferous coal swamps, where lycopsids like Lepidodendron and Sigillaria were buried faster than they could decay, sequestering vast carbon stores that became the world's great coal deposits.
That runaway carbon burial pushed atmospheric oxygen toward roughly 35 percent in the Carboniferous, relaxing respiratory limits on arthropods and enabling giants such as the dragonfly-like Meganeura and the millipede Arthropleura.

The Live Academic Debate

Several genuine debates persist. First, "what counts as the oldest forest" keeps shifting: Stein et al. (2007, 2012) elevated Gilboa; Stein et al. (2019, Current Biology) reported older, deep-rooted Archaeopteris at Cairo (c. 386 Ma); and Davies, McMahon & Berry (2024, Journal of the Geological Society) pushed the record to c. 390 Ma cladoxylopsid (Calamophyton) stands in the Hangman Sandstone of southwest England—each claim resting on differing criteria for "forest." Second, the causal role of trees in the Late Devonian mass extinctions is disputed: Algeo and Scheckler's land-plant/weathering-anoxia hypothesis is influential but challenged by those emphasizing volcanism, sea-level change, or oceanographic controls, and the magnitude of plant-driven CO2 drawdown is debated against models like GEOCARB. Third, the very definition of a "true tree" is contested—whether arborescence requires a bifacial cambium and true secondary wood (favouring Archaeopteris) or merely self-supporting woody stature (admitting cladoxylopsids like Wattieza and Calamophyton). These remain active, unsettled questions.

The Counterfactual

Without deep-rooted arborescent plants, the Devonian's enhanced continental weathering—and its consequent nutrient delivery to epicontinental seas—would have been muted. Algeo and Scheckler (1998) and subsequent geochemical work (e.g., Smart et al. 2023) argue that expanding forests drove riverine eutrophication, algal blooms, and bottom-water anoxia implicated in the Kellwasser and Hangenberg crises; absent trees, the Late Devonian marine extinctions might have been less severe or differently timed. The long-term CO2 decline and cooling that the "Devonian plant hypothesis" attributes to silicate weathering would likely have been slower, plausibly delaying the lush Carboniferous coal forests and the great Paleozoic oxygen rise that supported giant arthropods. Critically, secondary wood (lignified xylem from a bifacial cambium) was the evolutionary key; had cladoxylopsids alone persisted without Archaeopteris-grade wood and roots, vertical canopies and deep rooting would have remained limited, and the feedbacks on climate and soils correspondingly weaker. Much remains uncertain, since extinction causation is multifactorial and contested.

Myth vs. Reality

Myth: Archaeopteris was the first tree, and it shows up in the fossil record as a fully modern-looking forest tree.

Reality: Archaeopteris (Late Devonian, ~385-359 Ma) was long treated as the first 'modern' tree because Charles Beck's 1960 work linked its fern-like fronds to woody trunks previously called Callixylon, revealing a tree with conifer-like wood. But it was not the first tree. The 2007 description by Stein, Mannolini, Hernick, Landing and Berry of Wattieza (a cladoxylopsid from Schoharie County, New York, ~385 Ma) reconstructed an even earlier tree, and Middle Devonian trees from Gilboa and the Hangman Sandstone of SW England are older still. Archaeopteris is better described as among the first trees with extensive modern-style root systems, not the first tree overall.

Myth: Archaeopteris was a kind of early bird, like Archaeopteryx.

Reality: The two names are routinely confused but refer to completely unrelated organisms. Archaeopteryx is the famous Late Jurassic feathered dinosaur/early bird; Archaeopteris is a Devonian plant, an extinct progymnosperm tree. Both names derive from Greek roots referencing 'ancient' and 'fern/wing' (pteris/pteryx), which is why they look similar, but Archaeopteris is a tree, not an animal.

Myth: These first trees reproduced with seeds, like modern trees.

Reality: The earliest trees did not have seeds. Archaeopteris belonged to the progymnosperms, a group anatomically closer to seed plants (it had wood built from tracheids and rays much like conifers) but which still reproduced by dispersing spores, like ferns. Some species such as Archaeopteris halliana were heterosporous, producing two spore sizes, a condition seen as a precursor to true seeds. Seed plants evolved later; the first trees were spore-bearers with wood, an evolutionary transitional form.

Myth: The first trees grew the way modern trees do, adding solid wood in concentric rings around a stable trunk.

Reality: The earliest cladoxylopsid trees such as Calamophyton grew in a fundamentally different way. As shown by Xu and colleagues in their 2017 PNAS study of silicified trunks from Xinjiang, China, these trees had hollow trunks built from many separate vertical strands of woody xylem connected by softer tissue, rather than a single solid woody cylinder. As the tree grew, the strands expanded and the connecting tissue tore, so the base of the trunk repeatedly split and self-repaired, effectively collapsing inward in a controlled way. This is unlike the uniform ring growth of modern trees.

Myth: There was a single, sudden 'first forest' that appeared in one place at one moment.

Reality: The rise of forests was a gradual, geographically spread-out process, and the trees were ecologically varied rather than uniform. The Cairo, New York site (~385 Ma) is currently among the oldest known forest floors and is roughly two to three million years older than the nearby Gilboa forest (~382 Ma), and comparably ancient fossil forests are now also documented in SW England. At Cairo, researchers identified multiple distinct tree types and root systems occupying different microhabitats, indicating that early Devonian forests, like modern ones, were heterogeneous communities rather than a single founding stand.

Frequently Asked Questions

What was the first true tree on Earth?

Two extinct plants compete for the title depending on definition. Wattieza, a fern-like cladoxylopsid that grew at least 8 meters tall, is the oldest known tree, dated to about 385 million years ago in the Middle Devonian; its crown was matched to the long-known Gilboa stumps (Eospermatopteris) in fossils published in Nature in 2007. Archaeopteris, which appeared somewhat later in the Late Devonian, is often called the earliest 'modern' tree because it had a true woody trunk and conifer-like branching, and it formed the first widespread forests.

When did the first trees and forests appear?

True trees emerged during the Devonian Period, roughly 393 to 359 million years ago. The earliest known forests date to about 385 million years ago, represented by sites at Cairo and Gilboa in upstate New York. The Cairo fossil forest, announced in 2019, is currently considered the world's oldest known forest, slightly predating the nearby Gilboa site by one or two million years.

Where is the world's oldest fossil forest located?

The oldest known fossil forest was discovered in an abandoned quarry near Cairo, New York, and described in scientific publications in 2019. Dated to about 385 million years old, it preserves extensive root systems covering at least 3,000 square meters, with the largest root networks extending roughly 11 meters (36 feet) from the trunks. It lies about 40 kilometers from the famous Gilboa fossil stumps, also in New York.

What did the first trees look like?

They looked quite different from most trees today. Wattieza resembled a tree fern or palm, with a slender trunk topped by a crown of frond-like branches rather than flat leaves, standing around 8 to 10 meters tall. Archaeopteris had a genuine woody trunk that could reach 20 to 30 meters or more, with branching similar to modern conifers but bearing fern-like foliage. Neither produced seeds; both reproduced by spores.

How did Archaeopteris reproduce, and was it a real tree?

Archaeopteris was a progymnosperm, meaning it had wood like a modern tree but still reproduced by spores rather than seeds, making it transitional between ferns and seed plants. It was heterosporous, producing both larger megaspores (which gave rise to egg cells) and smaller microspores (which produced sperm). Its key innovation was a bifacial vascular cambium that let it grow outward in girth as well as upward, producing true wood much as living trees do.

How did the rise of the first trees change Earth's climate?

The spread of deep-rooted trees in the Devonian is thought to have transformed the planet's surface and atmosphere. Their roots accelerated the chemical weathering of rocks and the formation of soils, which drew down atmospheric carbon dioxide and contributed to a long-term decline in CO2 over the Paleozoic. Some researchers link the resulting nutrient runoff to ocean anoxia and the Late Devonian extinctions, and the cooling is associated with later continental glaciation, though the exact timing and magnitude of these effects remain debated.