How tree roots caused mass extinction

(ORDO NEWS) — Usually, when we imagine the cause of a mass extinction, we think of asteroids, volcanic eruptions, or, at worst, outbreaks of disease and famine. But sometimes even such “harmless” factors as the appearance of well-developed roots in terrestrial plants can trigger a deadly chain of events.

In the Devonian period , the first real forests appeared on Earth: tree-like horsetails, club mosses and ferns up to nine meters high grew along swampy river banks, and primitive gymnosperms , distant relatives of modern pines and firs, fought for a place under the sun on dry hills.

It seemed that an absolutely peaceful stage of terrestrial evolution was taking place, which later launched the development of large terrestrial vertebrates.

However, researchers suspect that the first forests unwittingly caused a series of mass extinctions that overwhelmed the Devonian reservoirs and claimed the lives of almost 70 percent of their inhabitants.

An international team of scientists from the United States and Great Britain analyzed the composition of rocks in the east of Greenland, formed at the bottom of a Devonian lake.

Sedimentary bottom rocks testified to alternating wet and dry periods in the “life” of the lake, while, most importantly, “dry” rocks contained large amounts of phosphorus – a chemical element present in all living cells on Earth.

Scientists have suggested that the Devonian droughts were deadly for primitive trees, whose weak root systems could not draw water from great depths.

As a result, the drainage of the lake led to the death of the roots that fed from it, and the returned water was saturated with nutrients that were washed into the ocean.

Such a phenomenon, called eutrophication, still exists today, although it is no longer the trees but human activities (such as overuse of fertilizers) that cause the water to “bloom”.

How tree roots caused mass extinction 2
Soil sampling in Greenland

Modern trees have developed a better root system that retains nutrients better in the soil. However, the threat of eutrophication has not gone away.

The intake of a large amount of nutrients into the reservoir leads to the rapid growth of microscopic algae, which not only poison the water, but also deprive it of oxygen, which leads to the mass death of plants and animals.

It is likely that Devonian life had to face the same problems, and the experience of the Earth 370 million years ago may serve as a warning to mankind of the real danger of excessive use of fertilizers and discharge of sewage into rivers.

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