How trees changed the world

"I WAS completely dumbfounded," says palaeontologist Bill Stein, recalling the moment he first set eyes on the newly discovered fossil. In front of him was an astonishingly well preserved tree, complete with trunk and branches, dating from 385 million years ago. Finding a near-complete fossil tree is rare enough in itself, but this was even more extraordinary. It came from the first forest on Earth.

The long-hoped-for Gilboa tree dates from the middle of the Devonian period (416 to 359 million years ago), a time of explosive evolutionary action among land plants. During this period they evolved from small, primitive forms that would have barely brushed your ankle into genuine trees up to 30 metres tall. And with the evolution of trees, they and all the other plants - hitherto confined to marshy environments - went on to conquer the surface of the planet.

These first forests changed the face of the Earth. Early land plants had already started leaking oxygen into the atmosphere, creating soils and providing food and shelter for animals, and the evolution of trees upped the pace of change. They weathered rocks, made soils deeper and richer, created complex habitats and changed the climate beyond recognition. By the end of the Devonian, an ecologically modern world had appeared.

The best place to catch a glimpse of this primitive terrestrial Eden is in the rolling hills around the village of Rhynie in Aberdeenshire, UK. Here the finely crystallised quartz of the Rhynie chert preserves in extraordinary detail an entire ecosystem that was engulfed and petrified by silica-rich waters from a volcanic spring 410 million years ago. The fossil plants still stand upright, and even their cells remain visible. Tiny creatures such as insects, centipedes, mites, harvestmen and spider-like trigonotarbids are preserved in immaculate detail. Some still cling to the stems on which they lived and died.......

by James O'Donoghue 

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