Lots of forests and swamps

Earth was never entirely covered in swamps or forest, but for periods of time specific growths were more numerous than others. Algae were followed by swamps, then by the forest that was dominant when humans conquered the planet.

470 million years ago: Algae were dominant

1 The first terrestrial plants were algae and mosses that extracted nutrients from the rocky ground, leaving chemical compounds which removed carbon dioxide from the air. 310 million years ago: Swamp produced coal

2 Swamps covered all terrestrial regions from the Equator to close to the modern Arctic Circle, where ferns grew. Most of Earth’s coal reserves formed during this period. Humans conquered a forested planet

3 Farming and the first cities originated when much of Earth was covered in wood. Six billion trees covered the planet and were important for the technology of early civilisations.