The Earth’s air is only breathable today because of moss-like plants that colonised the land 470 million years ago. And the mosses of Barrington Tops are a living link back to that life-sustaining event.
The moss enriched the atmosphere with oxygen and triggered a cycle that maintained its levels, paving the way to complex life.
Oxygen in its current form first appeared on Earth 2.4 billion years ago in what has become known as the Great Oxidation Event.
A team from the University of Exeter used computer simulations to show how the first land plants contributed to the Earth’s oxygen.
The earliest terrestrial plants were simple bryophytes, such as moss, which lack vein-like systems to transport water and minerals.
Factoring the properties of modern bryophytes into the simulations indicated that thanks to the ancient mosses, modern levels of atmospheric oxygen would have been achieved by 420 to 400 million years ago.
The emergence of the plants eventually led to a stable and self-sustaining cycle of oxygen flowing between sedimentary rocks, living things and the atmosphere.
Today, the air we breathe consists of of 78 per cent nitrogen and 21 per cent oxygen, with smaller amounts of argon, carbon dioxide, water vapour and trace gases.
As well as making the air breathable, oxygen generates the ozone layer that protects life on Earth from the harmful effects of ultraviolet radiation from the sun.
“It’s exciting to think that without the evolution of the humble moss, none of us would be here today,” said lead scientist Tim Lenton, from the University of Exeter.
“Our research suggests that the earliest land plants were surprisingly productive and caused a major rise in the oxygen content of the Earth’s atmosphere.”
(Article courtesy of