Humans may owe Earth's oxygen-rich atmosphere to moss, which dramatically increased oxygen levels some 400 million years ago, according to a new study published in the Proceedings of the National Academy of Sciences on Monday.
The Guardian reported that the study, which was led by University of Exeter climate change professor Tim Lenton, suggested that the planet was mostly water when "rock-hugging" green moss evolved on exposed dry land during the Ordovician Period.
The moss was able to use photosynthesis to boost atmospheric oxygen to roughly the same level enjoyed today.
"Oxygen in its current form first appeared in Earth's atmosphere some 2.4 billion years ago, in an incident known as the Great Oxidation Event," said a statement from the University of Exeter. "However, it was not until roughly 400 million years ago that this vital compound first approached modern levels in the atmosphere. This shift steered the trajectory of life on Earth and researchers have long debated how oxygen rose to modern concentrations."
Researchers were able to use computer simulations to estimate that moss and other non-vascular plants played a significant role in the formation of life on the planet.
"It's exciting to think that without the evolution of the humble moss, none of us would be here today," Lenton said in the University of Exeter statement. "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."
The Guardian wrote that at the time moss emerged, life was concentrated in the sea and most of the current United States was underwater. The Appalachian mountains, for example, were "arcs of rocks in the tropic ocean," noted The Guardian.
"It's very hard to get direct evidence of what's on land, because most stuff is preserved in ocean sediments, so we rely on freaky, unusual terrestrial preservation," Lenton told The Guardian. "But what we know is there was some productivity on the land."
"What we are seeing are the first true plants – mosses, liverworts, bryophytes – entering what was previously Matworld. You could think of them as creating thicker, more luscious carpets."
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