Ancient fossil leaves image by Dr Jennifer McElwain
Dr Jennifer McElwain, UCD School of Biology & Environmental Science, and an international team of researchers have unearthed striking evidence of a sudden collapse in plant biodiversity from 200-million-year-old fossil leaves collected in East Greenland. The discovery raises new concerns about the dangers of global warming.
The research, which was funded by a Marie Curie excellence grant and features in the current issue of the journal Science, reveals that a relatively small rise in carbon dioxide, caused the Earth’s temperature to rise resulting in great loss of plant life at the boundary of the Triassic and Jurassic periods.
Global warming has long been considered the cause of extinction, however the new findings suggest that much less carbon dioxide gas in the atmosphere may be needed to drive an ecosystem beyond its tipping point.
Using a technique developed by Peter Wagner of the Smithsonian Institution National Museum of Natural History, the researchers were able to detect, for the first time, very early signs that these ancient ecosystems were already deteriorating, before plants started going extinct.
By the year 2100, it is expected that the level of carbon dioxide in the modern atmosphere may reach as high as two and a half times today's level. ‘This is of course a 'worst case scenario,’ says McElwain, the paper's lead author, ‘but it's at exactly this level which we detected the ancient biodiversity crash’.
‘We must take heed of the early warning signs of deterioration in modern ecosystems. We've learned from the past that high levels of species extinctions - as high as 80 percent - can occur very suddenly, but they are preceded by long interval of ecological change.’
Dr McElwain cautions that sulphur dioxide from extensive volcanic emissions may also have played a role in driving the plant extinctions. 'We have no current way of detecting changes in sulphur dioxide in the past, so it's difficult to evaluate whether sulphur dioxide, in addition to a rise in carbon dioxide, influenced this pattern of extinction,' she said.
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