World’s first forest leaves its carbon footprint
A little over 380 million years ago, in what today is North America, something happened that would change the world for ever. A tree grew, and beside it another, and another.
At this site, just north of New York, there was soon a forest. The fossilised remains, which scientists said yesterday were the oldest known forest, mark the point at which the planet began to suck in carbon. In the years that followed trees would take over the land. With their march the atmosphere would cool, ice caps appeared at the poles, and the planet as we know it began to resemble the one we see today.
But it began, Christopher Berry of Cardiff University said, with these first trees. ‘‘The basic thing about trees is they take carbon dioxide out of the atmosphere,’’ he said. ‘‘They turn it into a planet a lot like ours.’’
There is, he admitted, no clear definition of a tree, except that you know it when you see it. ‘‘It’s an upright woody plant with an upright trunk,’’ he said. ‘‘And it’s of considerable stature.’’
Twenty million years before the forest appeared there would have been few things of any stature, considerable or otherwise. Plants were smaller, more slender and less selfsupporting, and lived in an atmosphere with several times more carbon than today.
These trees, found fossilised at the bottom of a quarry, changed that. A forest, of sorts, appeared. There were clumps of Cladoxylopsid, 10 metres tall and with no leaves. Berry said it was particularly exciting to see the root system of a tree called
Archaeopteris, which would have looked a little like a conifer but with fern-like leaves. ‘‘This is the first upright tree with a solid wood trunk. It was really massive, woody, and was permanently digging its way through the soil and processing it.’’ As well as turning carbon into wood its roots worried at the soil, having a long-term impact. ‘‘The roots attack the soil with acids and other things,’’ Berry said. ‘‘They take carbon from the atmosphere and turn it into carbonic acid, which is washed through the soil into the river and down to the sea where it is used by little animals to make their shells.’’
After these little animals died their shells become limestone, locked in the ground. More than 150 million years before the dinosaurs, this process helped to prepare the way for them.
The future of the forest itself, though, was less rosy. Berry said it was probably killed off by a sudden flood.