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Forests - the Foundation of Our Biosphere |
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This is a land-mark article of the first order. Not so much for identifying the first shade tree of the Earth, but for what is mentioned in passing. What is of crucial importance here is the recognition that 3 billion years of marine photosynthesis had resulted in only 5% free oxygen in the archaic atmosphere - and that with the advent of terrestrial photosynthesis (and Archaeopteris), and within only 50 million years, the free oxygen level of the atmosphere rose to 20%, while the carbon dioxide content dropped from 10% to 1 per cent. |
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This is of course what I have been saying in these pages all along and, as far as I know, was the first to do so. Here then, we now have solid scientific proof that the Earth's forests - and NOT the oceans, as still widely and erroneously believed in science - generate about 75% of the free oxygen of our atmosphere, and absorb by far most of the carbon dioxide produced in our biosphere.
This also validates, as so many other discoveries, the assertion that doubling the world's forested areas will end the greenhouse effect, end the desert effect and the ultraviolet effect. Indeed, with this proof we can now see that the world's forests are - or have been - the foundation of our biosphere, of the richly oxygenated biosphere our kind and all oxygen breathing Life has evolved in.
And that we have eradicated fully 80% of the world's original forests, and continue to loose what is left at prodigious rates, can only lead to a desert planet - and the collapse of the biosphere our kind has evolved in.
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Original Article:
370 Million Years Ago, the First Modern Tree
Making its evolutionary entrance 370 million years ago, Archaeopteris looked something like a Christmas tree and may have transformed the environment on this planet with the first bountiful swaths of shade.
“When it appeared,” says Stephen Scheckler, a professor of biology and geological sciences at Virginia Polytechnic Institute, “it very quickly became the dominant tree all over the Earth. On all of the land areas that were habitable, they all had this tree.”
Analyzing a trove of fossilized Archaeopteris wood from Morocco, Scheckler, Brigitte Meyer-Berthaud of the Institut de l’Evolution de Montpellier in France and Jobst Wendt of the Geological and Paleontological Institute in Germany declare the ancient tree is actually the earliest-known modern tree with buds, reinforced branch joints and branched trunks similar to today’s timber. The researchers report their findings in the April 22. 2001 edition of the journal Nature.
The branches and leaves of Archaeopteris resembled a fern. The wood was like conifers. Plants first made it out of the water to land about 500 million years ago, evolving into mosses and, later, ferns. Then came the move upward. Several varieties of trees, including Archaeopteris emerged around 370 million years ago.
“When plants grow taller, they have biomechanical problems of supporting the additional weight,” Scheckler says. “Plants compensate for that by adding tissues in the right places and knitting them together in the right way.” But they didn’t all do it the same way. “One of the surprising things,” Scheckler says, ”is there were several different designs of tree.” The fossils were found lying on the ground near the town of Erfoud.
While the other types of trees quickly went extinct, Archaeopteris made up 90 per cent of the forests. With trunks up to 3 feet wide, the trees grew perhaps 60 to 90 feet tall. Unlike present-day trees, Archaeopteris reproduced by shedding spores instead of seeds.
Although pieces of Archaeopteris have been found around the world, the fossils didn’t clearly show how the tree was put together. Wendt first reported the Moroccan fossils back in 1991. Last year, Wendt, Meyer-Berthaud and Scheckler returned to that barren, mountainous region to bring back more fossilized wood. “They were on the ground,” Meyer-Berthaud recalls. “We don’t understand why no one before us found them. They are everywhere.”
This area of southeastern Morocco, now desert, had once been a sea. The 40- to 50-year-old trees had toppled over, washed out into the water, then sank and fossilized in the sediment. The scientists piled into their Land Rover more than 150 pieces, the biggest find of Archaeopteris ever.
Under the microscope, Meyer-Berthaud saw bud-like structures on the trunk and branches that could produce new branches in case the tree was injured. “That’s the real innovation they’re showing,” Scheckler says, “the ability to sprout new buds if injured. It gives them essentially a perennial life span.” The researchers also found that the branches of Archaeopteris attach the same way as those of present-day trees. The bases of the branches swelled into a reinforcing collar, and the internal layers of wood interlocked to resist breaking.
That, in turn, meant that Archaeopteris would have been able to stretch out its branches and canopy of leaves. And the trees’ fallen, decaying leaves nourished life in the streams. “This is very important in the evolution of terrestrial ecosystems,” comments Gar Rothwell, professor of environmental plant biology at Ohio University. “This was the first type of plant able to produce a canopy-type tree.”
Not coincidentally, the level of carbon dioxide - breathed in by plants - was dropping in the atmosphere, from 10 percent to 1 percent, while the level of oxygen was rising from 5 percent to 20 percent. “The plant cover is changing the Earth in ways that make it much more like a modern Earth,” Scheckler says.
Then, about 345 million years ago, Archaeopteris died out. Its dominance of the early forests may have made it susceptible to being wiped out by disease. “We don’t know why it did,” Scheckler says, “but we know it was vulnerable. It just vanished, ka-poof.” Other trees, close relatives but not direct descendants of Archaeopteris, filled the gap, and forests have been on Earth ever since.
[Source: ABC NEWS, April 22. 2001; by Kenneth Chang]
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