What caused the Great Coal Crash of 300 million years ago?S

Coal generates nearly half the electricity we use in the United States. We all depend on the fossilized remains of plants — but the vast majority of the coal in the ground comes from a single era, from 360 to 300 million years ago.

What caused the Great Coal Crash of 300 million years ago, that stopped coal from being formed? As usual, you can blame evolution.

Top image: Coal power plants by London Permaculture/Flickr

Coal is primarily comprised of the plant's lignin, the rigid cell walls that are left behind after the rest of the plant gets eaten away by fungi. The lignin accumulates as peat, then gets compressed into coal. However, somewhere around 300 million years ago, something happened to the fungi. The first white rot fungi appeared on the scene, able to digest the lignin. This meant much less coal — because the entire biomass was digested, and released as carbon dioxide.

This information came to light thanks to the genome sequencing of 31 Agaricomycetes fungi, both brown and white rot. Through a comparative analysis of these genomes, researchers were able to spot that around 290 million years ago, fungi that could break down lignin arrived on the scene. And while it may seem rather mundane to figure out why we have more coal from x million years ago rather than y, it does show the huge amounts of information we can gather from genomic analysis — and that information could help us engineer fungi that break down things that we need broken down.

Image: Scanning electron micrograph of aspen wood that is being attacked by the white rot fungus Punctularia strigosozonata, courtesy of A. Justo and D. Floudas