In a cluster of coal mines in eastern Illinois, researchers have discovered the fossilized remains of ancient rainforests that date from the Carboniferous era, including one forest that stretched for 39 square miles. Researchers say the forests date from both before and after an episode of intense global warming that occurred about 306 million years ago, and may shed light on the ecosystem‘s reaction to the drastic climate shift.
Researchers published a report on the first fossilized rainforest last year, but announced this week at the British Association’s Festival of Science that they have since come across five more patches of ancient woods. Says paleontologist Howard Falcon-Lang: “Three of the forests predate global warming and the rest follow it, so we can compare the ecology of those rain forests to see what the effect of global warming was.” During that period the Earth’s climate flipped from being covered with large polar icecaps to a greenhouse state that was completely ice-free, he added [National Geographic News].
The six forests all date from the end of the Carboniferous period, when the biomass that eventually formed much of the world’s coal deposits was deposited. Now that the coal seams in the Illinois mines have been excavated (what were, essentially, the compacted soils of the forests), it is possible to go into the tunnels and look up at what would have been lying on the forest floors. “It’s kind of an odd view looking at a forest bottom-up. You can actually see upright tree stumps that are pointed vertically up above your head with the roots coming down; and adjacent to those tree stumps you see all the litter” [BBC News] says Falcon-Lang.
The fossil record shows that the older forests were filled with enormous club moss trees, Falcon-Lang says, but those trees were no longer present in the forests that date from a few million years later. He said it appeared that the huge trees suffered enormous stress and died out when faced by global warming. “We are beginning to show there appears to be a threshold in ancient rainforest systems beyond which the whole system begins to unravel quite quickly,” he said. “The rainforest dramatically collapses during this period of warming. This was very, very extreme global warming. Giant club moss trees vanished overnight to be replaced by rather weedy fern vegetation” [The Times].
Image: Howard Falcon-Lang