Earliest Plants Are Responsible For Modern Day Oxygen Levels

While oxygen first appeared in Earth's atmosphere 2.4 billion years ago, it took another two billion years to reach the levels we breath in today.

Now a researchers believe they have identified what helped lead to this dramatic increase in oxygen on our planet - moss.

Scientists at the University of Exeter suggest moss-like plants were among the first to colonise the land and triggered oxygen in the atmosphere to increase.

The first plants are thought to have colonised the land from the oceans around 470 million years ago.

These first terrestrial plants were non-vascular plants, known as bryophytes, which include moss.

They say that the emergence of these plants increased the intake of organic carbon into sedimentary rocks – the primary source of atmospheric oxygen.

The scientists calculated that Earth's early plant biosphere could have produced roughly 30 per cent of the modern carbon take up from the atmosphere on land by around 445 million years ago.

This drove up oxygen levels and established a new, stable oxygen cycle.

The researchers estimate that within 50 million years of this, oxygen levels had reached modern levels.

Profesor Tim Lenton, who led the study, said: 'It's exciting to think that without the evolution of the humble moss, none of us would be here today.'

The earliest plants on earth were bryophytes - plants such as moss - which are non-vascular, meaning they do not have vein-like systems to move water and minerals around the plant.

The researchers used computer simulations to estimate when oxygen levels reached that of modern day.