CLUES TELLING us what to expect from climate change are easily found, both in the fossil record of plants but also in the genes of animals living around us today. These clues tell us that overwhelming changes are on the way with massive species extinctions and unparalleled changes to our environment.
The public was shown these clues in an intriguing session yesterday on the final day of the EuroScience Open Forum in Turin. They exist in 200 million-year-old plant fossils dug out of the stone in Greenland – once covered by a lush subtropical forest; can be seen in fish that become male or female in response to temperature; and are read in the genes of bats, the second most varied species of mammal in the world.
“The earth’s climate is changing and temperatures are rising as carbon dioxide levels rise,” said Dr Jennifer McElwain of University College Dublin, who organised and began the session. “Carbon dioxide is higher than at any time in the last 16 million years.”
She analysed plant fossils from a location on Greenland’s southeastern coast where the average summer temperature stands at 16 degrees. But the whole area was lush with trees and undergrowth when the region’s temperature was just three degrees higher than today, she said.
“I am using the past to gauge how these plants responded in the geological past when carbon dioxide rose to levels higher than they are now,” she said.
She looked for fossils of plants that grew in the region when the temperature difference was three, four and six degrees higher than today.
Her seven-year study involved about 5,000 fossils such as ginkgos and broad-leafed conifers.
Plants change in direct response to carbon dioxide levels, adding more pores or “stomata” if levels are low or fewer if levels of carbon dioxide are high. The pores let carbon dioxide into the leaf and allow water to escape to keep the plant cool. “We can use this very simple relationship,” she said.
Carbon levels were, at their worst, five times today’s levels, when temperature differences reached six degrees higher than today, caused by increased volcanic activity. “With six degrees we see complete ecological collapse,” she said. Over a period half of all land species and 60 per cent of marine species went extinct.
Our CO2 levels are moving towards these high values. “By the end of 2100 we will be getting close to the tipping point seen at the end of the Triassic period,” she said. Many existing plants disappeared to be replaced by the survivors. “We see a completely new ecology emerging, new species developing during the peak warmth.”
Dr Stefano Mariani of UCD continued the talk with his research into fish that, as part of their normal life, change sex. About 1 per cent of fish can do this and they appear right across the range of species, implying there must be some evolutionary advantage to being able to do this. “The big question is why does it exist, why does it keep happening,” he said.
Dr Mariani showed that in fact sex-changing species have an advantage over those that don’t change during times of stress caused by environmental change or, as now, through over-fishing.
Dr Emma Boston of UCD and also Queen’s University Belfast discussed her work studying the genetic blueprint of bats. It is possible to use a genome as a “molecular clock” to track backwards into the evolutionary past and because of the great variety of bat species they offer an ideal way to monitor environmental impacts.
She described how the number of mammal species, including bats, “exploded” when the dinosaurs died out suddenly 65 million years ago. She can also see the effect of a sudden temperature spike about 52 million years ago during what’s known as the Paleo-Eocene Thermal Maximum.
Climate change will make things difficult for the bats, she says. “We are going to see extinctions. Many bats are very specialised,” she said.