LIFE × CLIMATE

The First Forests

~385 million years ago

Phanerozoic · Paleozoic · Devonian

A quarry floor in New York State, mapped over twelve hundred square metres, shows what a Devonian forest actually was. Tree-fern-like plants at least eight metres tall stood in a mixed-age stand, shedding their branches whole as litter. Woody creepers ran between them and probably climbed them. Deep-rooted trees of another kind, Archaeopteris, grew nearby. It was a wetland, short-lived, and repeatedly knocked down.

Why it matters

Forests are usually credited with pulling the carbon dioxide out of the Devonian air. Measured from fossil plants, the air was already down to 525 to 715 parts per million before the trees arrived, and modelling the deep roots does not add much: the drawdown seems to belong to the shallow-rooted plants that came first. What the forests changed was the land itself, and what could live on it.

Dating & uncertainty

Fossil soils at Gilboa and Cairo, in New York State, preserve rooted trees in life position in the Middle Devonian. How much carbon dioxide those forests drew down is contested: shallow-rooted plants may have done most of that work earlier.

Sources

1. Stein et al. (2007), Nature · Giant cladoxylopsid trees resolve the enigma of the Earth's earliest forest stumps at Gilboa
2. Stein et al. (2020), Current Biology · Mid-Devonian Archaeopteris roots signal revolutionary change in earliest fossil forests
3. Stein et al. (2012), Nature · Surprisingly complex community discovered in the mid-Devonian fossil forest at Gilboa
4. Dahl et al. (2022), Nature Communications · Low atmospheric CO2 levels before the rise of forested ecosystems

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