Evolution of Tree Roots May Have Led To Mass Extinctions
Geologists have found parallels between ancient global extinction events and modern threats to Earth's oceans
A study has found that the evolution of tree roots 300 million years ago triggered mass extinction events through the same chemical processes created by pollution in modern oceans and lakes.
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A study led by IUPUI scientists with colleagues in the United Kingdom suggests that the evolution of tree roots may have triggered the massive extinctions that rocked Earth's oceans during the Devonian period 300 million years ago.
Evidence for this new view of an unusually unstable period in Earth's prehistory is reported in the Geological Society of America Bulletin. Professor Gabriel Filippelli, chancellor of Earth Sciences in the School of Science at IUPUI and Ph.D. Matthew Smart led the study.
Our analysis shows that the evolution of tree roots flooded past oceans with excess nutrients, causing massive algae blooms. These rapid and destructive algae blooms could deplete much of the oceans' oxygen, triggering catastrophic mass extinction events, says Filippelli.
The process described in the study is scientifically known as eutrophication. Fertilizers and other nutrients are becoming excess nutrients, a small-scale phenomenon that is currently fueling vast dead zones in the Great Lakes and Gulf of Mexico. Agricultural runoff can trigger massive algae blooms that consume all of the water's oxygen.
The difference is that these past events were fueled by tree roots. They draw nutrients from the soil during growth and dump them into the ground water during spontaneous decomposition.
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Their remains are found around the world, including samples used in the study from sites in Greenland and the northeast coast of Scotland, based on chemical analysis of rock deposits from ancient lake beds.
They were also able to distinguish between wet and dry cycles based on climatic cues, or soil formation root growth, with wet cycles with more weather indicating more roots and dry cycles with less weather indicating fewer roots.
Most importantly, the team found that dry cycles coincided with high levels of phosphorus. Dying roots indicate that they release their nutrients into the planet's waters during these times.
Probing more than 370 million years into the past isn't easy, Smart said. But rocks have long memories, and there are still places on Earth where you can use chemistry as a microscope to unlock the secrets of the ancient world.
The evolution of the first tree roots is characteristic of Archeopteryx in light of the phosphorus cycles occurring at the same time. Researchers were able to trace the decline of the first plant that grew its leaves to a height of 30 feet. The main anumanum tree roots behind the Devonian period extinction events.
Luckily, Filippelli says, modern trees don't cause such havoc because nature has since developed systems to balance the effect of rotting wood. The depth of modern soil also contains more nutrients than the thin layer of dirt that covered ancient land.
The study's authors note that others have argued that pollution from other organic wastes, such as fertilizers, manure and sewage, is pushing Earth's oceans to the brink of anoxia, or complete lack of oxygen.
These new insights into the catastrophic results of natural events in the ancient world can serve as a warning about the consequences of similar situations arising from human activity today, says Fillipelli. Abiogenic
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Materials provided by Indiana University.
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