Fungi involved in mass extinction
According to New Scientist magazine (August 20 2011) climate change could make trees much more suceptible to a cataclysmic fungal attack.
During Earth's biggest mass extinction 250 million years ago, usually tame soil fungi ran amok, decimating most of the world's trees. The Permian extinction saw 95 per cent of species wiped out. dwarfing the K-T extinction that ended the dinosaurs' reign. Mark 5ephton of Imperial College London, said a knock-on effect of the vast volcanic eruptions that triggered the extinction was a global fungal plague.
Climate change and other human activities are stressing plants around the world, potentially putting them at risk. "Dramatic changes can occur when you stress an ecosystem too far," he says.
Sephton has long been intrigued by a mysterious layer of fossilised strands in rocks that formed at the end of the Permian epoch. "You can find it all round the globe," he says, "and you don't see it any where else in the geological record." The strands were first thought to be opportunistic fungi that feasted on plants after they died, although some researchers thought they were algae, which couldn't have eaten the trees (Polynology, 001: 10.2113/0260035).
To settle the question, Sephton teamed up with Henk Visscher of Utrecht University in the Netherlands and Cindy Looy of the University of California, Berkeley. They found that the strands looked just like a group of modern fungi called Rhizoctonia, implying a fungal takeover took place.
Rhizoctonia lurks in soils, waiting to attack plants whose immune systems are weakened. Sephton thinks their Permian counterparts attacked and killed trees, which would have been weakened by heat stress, drought and acidification due to the volcanic eruptions (Geology, 001: 10.1130/g3217B.l).
Fungi's role in the Permian extinction is a warning, says Sephton. "Climate change is stressing plants around the world. which could put them at risk of a fungal attack"
But it's not clear that fungi could once again run amok. Steven Running of the University of Montana in Missoula, points out that most modern plant pathogens can only attack one genus, or even species, limiting the damage they can do.
The closest modern-day analogue is the heavily polluted Black Triangle in eastern Europe. Acidification from Soviet-era industry killed or damaged all the trees, which were then set upon by fungi.