CLIMATE × LIFE

The Coal Forests Break Up

~305 million years ago

Phanerozoic · Paleozoic · Carboniferous

The wet equatorial forests that made most of the world's coal broke into islands as the climate dried. Amphibians, which still had to lay eggs in water, lost ground. Amniotes, which did not, kept theirs.

Why it matters

The received story has the surviving tetrapods trapped in separate pockets and diversifying there. Counted again with the uneven sampling corrected, the opposite comes out: species richness falls across the Carboniferous boundary, and the animals that follow are more widespread than before, not less. Something did happen to the tetrapods. It was a thinning, and then a spreading, and the amniote egg is the likeliest reason the spreading was possible.

Dating & uncertaintyDisputed

The forests certainly fragmented as the climate dried. What it did to animals is argued: one reading has tetrapods becoming endemic and diversifying in isolated pockets; a later reanalysis correcting for uneven sampling finds the opposite, a fall in diversity followed by wider ranges.

Sources

1. Sahney, Benton & Falcon-Lang (2010), Geology · Rainforest collapse triggered Carboniferous tetrapod diversification in Euramerica
2. Dunne et al. (2018), Proceedings of the Royal Society B · Diversity change during the rise of tetrapods and the impact of the Carboniferous rainforest collapse
3. Berner et al. (2003), Annual Review of Earth and Planetary Sciences · Phanerozoic atmospheric oxygen

Earth history as one day

22:23:151 h 37 min before midnight

if Earth’s 4.54 billion years were compressed into a single day