Earliest Land Plants 400 Million Years Ago Possibly Modified Earth's Climate Regulation

A new study led by the University College London and Yale researchers recently showed that the arrival of the first land plants roughly 400 million years ago might have changed how this planet is naturally regulating its own climate.

According to a SciTechDaily report, the carbon cycle, the process through which carbon moves between oceans, rocks, living organisms, and the atmosphere, acts as the natural thermostat of Earth, regulating its temperature over long periods.

In this new study, researchers examined samples from rocks spanning the past three billion years and discovered evidence of a dramatic change in the manner this cycle worked roughly 400 million years back when plants began colonizing land.

The study authors specifically noted a change in the chemistry of seawater recorded in the rock that specified major shifts in the clay's global formation, the "clay mineral factory," from the oceans to the land.

ALSO READ: Global Emissions Drop by 7%, But Climate Change Experts Advise Not To Celebrate Just Yet

Clay Formation

Since the formation of clay in the ocean results in carbon dioxide being emitted into the atmosphere, while clay on land is considered a byproduct of chemical weathering that takes out carbon dioxide from the air, this decreased amount of carbon in the atmosphere resulted in a cooler planet, not to mention a seesawing climate, with interchanging ice age and warmer periods.

In their study, "A lithium-isotope perspective on the evolution of carbon and silicon cycles," published in Nature, the authors suggested the switch resulted from the spread of the first land plants keeping soils and clays on and preventing carbon from being washed into the ocean, and by the growth in marine life through the use of silicon for their skeletons and cell walls, like sponges, one-celled algae and a group of protozoa also known as radiolarians.

UCL Earth Sciences' Dr. Philip Pogge von Strandmann, the study's senior author said, their research proposes that the carbon cycle operated fundamentally differently from most of the history of Earth compared to the present day.

The shift, said the senior author explained, which took place gradually from 400 to 500 million years back, seems to be associated with two major biological innovations at the time: the land plants' spread, as well as the growth of organisms, that extract silicon from water to make their skeletons and cell walls.

Prior to this change, atmospheric carbon dioxide stayed high, resulting in a stable greenhouse climate. Since then, the climate has bounced back and forth between warmer periods and ice ages.

Such a change promotes evolution, and during this period, the complex life's evolution fast-tracked, with land-based animals that formed for the first time.

Naturally Occurring Isotopes

A similar Phys.org report said, in the study, the authors measured lithium isotopes in 600 rock samples taken from many different sites all over the world. Essentially, lithium has two stable isotopes which are occurring naturally.

Clay is forming on land as a chemical weathering residue, the main long-term process through which CO2 is eliminated from the atmosphere.

This occurs when atmospheric carbon combines with water to form a weak acid, carbonic acid, which falls to the ground as rain.

It is also dissolving rocks, emitting ions, which include calcium ions that flow into the ocean. Ultimately, the carbon is locked up in rocks on the ocean floor.

When there is clay formation in the ocean, carbon stays in the water, and eventually, it gets released into the air as part of the continuous carbon exchange, occurring when air meets water.

Related information about the Earth's climate is shown on PBS NewsHour's YouTube video below: