LIFE × CLIMATE
The First Forests
~385 million years ago
Phanerozoic · Paleozoic · Devonian
The Gilboa forest, about 385 million years old and long cited as the Earth's oldest, is known from stumps that twelve hundred square metres of fossil soil preserve where the trees grew, in a quarry in New York State.
The Gilboa forest is a fossil forest uncovered in a quarry in New York State and long cited as the Earth's oldest forest. Researchers mapped its floor over a continuous surface. Twelve hundred square metres of fossil soil, or palaeosol, preserve the stumps in life position, that is, where the trees grew, and researchers reconstructed the structure of the forest from them. The trees were cladoxylopsids, which resembled tree ferns and stood at least eight metres tall. They were of mixed ages and shed whole branches, which made up the litter, the layer of dead plant matter on the ground. Woody lianas, climbing plants, ran between the trees and probably climbed them. The Gilboa forest grew in a wetland that was short-lived and repeatedly disturbed. Nearby, at Cairo, is an older forest, the oldest yet identified. Its trees were of another kind, Archaeopteris, with deep roots.
Why it matters
Forests are ordinarily credited with drawing carbon dioxide out of the atmosphere of the Devonian period. The shallow-rooted plants that preceded the forests may have removed most of that carbon dioxide. The forests transformed the soil itself and what could live in the soil.
Dating & uncertainty
Palaeosols preserve Middle Devonian trees rooted in life position at Gilboa and Cairo, in New York State. The quantity of carbon dioxide these forests removed is disputed. From fossil plants, Dahl and colleagues (2022) estimate an atmospheric concentration of only 525 to 715 parts per million, or molecules of carbon dioxide per million molecules of air, before the arrival of trees. Modelling the deep roots adds little to the removal. Shallow-rooted plants may therefore have removed most of the carbon dioxide earlier.
Earth history as one day
21:57:532 h 2 min before midnight
if Earth’s 4.54 billion years were compressed into a single day