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Ecologists follow the footprints of Scott

March 26, 2003

Important new data from the plant fossil record that are helping ecologists to improve the accuracy of climate change models will be announced at the British Ecological Society symposium at the Society for Experimental Biology's annual meeting, being held at the University of Southampton between 1 and 4 April 2003.

Dr Colin Osborne and his colleagues Dr Stuart Brentnall and Professor David Beerling of the University of Sheffield will tell the symposium (in session P7.12) that they have developed a new computer model that uses data from the annual tree rings in fossilised wood to reconstruct a virtual forest from 50 to 250 million years ago (the last period when the Earth's atmosphere was high in carbon dioxide, one the gases associated with global warming). These prehistoric forests provide vital clues about what the Earth's climate was like millions of years ago - data that could significantly improve the accuracy of models currently used to predict future climate change.

Scientists use two ways to study what the Earth's climate was like millions of years ago: they can look to plant fossils for evidence, or they can look backwards in time using the models developed to predict future climate change. The two methods, however, do not produce the same results. According to Dr Osborne: "There is a big discrepancy between climate model simulations of the ancient Arctic and Antarctic, and fossil evidence of past climates at these high latitudes. This is worrying because it highlights our ignorance about the workings of the global climate system, the last time that global warming gripped the Earth."

One possible reason for the discrepancy is that the models do not take enough account of the influence of vegetation on climate at high latitudes. "Compared with unvegetated land, forests absorb more sunlight and release more water into the air, making the climate warmer and wetter. This could be the missing link," Dr Osborne says.
By analysing the properties of cells in fossilised wood, Dr Osborne and his team can tell how long the tree in question kept its leaves. The length of time a tree remains in leaf both depends on - and in turn influences - the climate. "If a plant builds leaves to last a long time, it needs to invest a lot of energy in them to make them durable. But tough leaves are also less physiologically active than short-lived leaves, exchanging less carbon with the atmosphere, and releasing less nitrogen back to the soil when they are finally dropped. If leaves live fast, they die young," Dr Osborne explains.

Dr Osborne and his colleagues are following in the brave footsteps of Captain Scott, but hope that their work will not be similarly ill-fated. Scott was one of the first people to find evidence of prehistoric Antarctic forests. Those who discovered the bodies of Scott and his party in November 1912 also found 35 lbs of leaf fossils on their sledge. According to Scott's diary, they had collected the fossils from the Beardmore Glacier on their way back from the South Pole.

Society for Experimental Biology