A group of scientists from the Lamont-Doherty Earth Observatory at Columbia University analyzed a wide range of data to understand how the distribution of palm trees around the planet depends on the global temperature.
Palms are an unofficial symbol of tropical regions, but, according to experts, soon the time will come when they begin to grow in the north. Tammo Reichgelt, in collaboration with David Greenwood of the University of Brandon and postgraduate student Christopher West of the University of Saskatchewan, studied the distribution of palm trees over climatic zones. In their opinion, knowledge about these plants can be useful for forecasting the development of landscapes and ecosystems.
“Palms have been and remain sensitive indicators of climate change,” says Greenwood. – We are increasingly discovering that they grow in unconventional places, such as, for example, the foothills of the Swiss Alps. This suggests that the frosts are not as strong as they used to be. ”
The study, published in the journal Nature’s Scientific Reports, says that the “scatter” of palm trees on the planet depends on the average temperature of the coldest month in the region – it should be above 2 degrees Celsius or 36 degrees Fahrenheit. And as the climatic zones are now shifting to the north, the “habitat” of vegetation is also changing.
“For example, it’s too cold in Washington for palms today, as the average temperature in January does not exceed 34 degrees Fahrenheit,” Reichgelt said. “But we think that in the near future we can expect an expansion of the range of their distribution across America, because the temperatures are gradually growing.”
Scientists have found that the permissible temperatures of plants for survival depend on their evolutionary heritage: the frost resistance of a palm tree determines its specific kind and place on the genealogical tree. Moreover, the obtained data helped to know what the climate of the Earth was in the past: the presence of palm trees in the annals of fossils indicates that previously the world temperatures remained at the lowest possible level – from 2 to 5 degrees Celsius.
“If we correctly determine which sub-group of the palm family is a fossil, then with the help of our data it is possible to find out the average temperature in which this tree once grew,” Reichgelt says. “Interestingly, about 50 million years ago palm trees could be found in Antarctica, which means that the region was once almost tropical.”