When plants first ventured onto the land, evolving from freshwater-dwelling algae, more than 500 million years ago, they transformed the planet. By drawing carbon dioxide from the air, they cooled Earth, and by eroding rock surfaces they helped build the soil that now covers so much land.

These changes to the planet’s atmosphere and land surface paved the way for the evolution of the biosphere we know. Land plants make up around 80 percent of Earth’s biomass.

The pioneering plants were small and moss-like, and they had to overcome two big challenges to survive on land: avoiding drying out, and surviving the Sun’s harsh ultraviolet light.