Ice Age ‘Spa’ Kept Trees Alive in Freezing Conditions<\/b><\/p>\n Fossils from an ice age \u201cspa\u201d reveal a cluster of hot springs kept trees alive in the frozen Alps<\/p>\n<\/div>\n By Tom Metcalfe<\/a><\/p>\n An ice age “spa” like the one shown in this artist’s conception may have existed long ago in what is now the Czech Republic.<\/p>\n<\/div>\n Illustration by Jiř\u00ed Svoboda<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/div>\n A \u201ctree spa\u201d created by hot springs in what is now the Czech Republic may have served as a refuge for plants\u2014and possibly animals\u2014during the last ice age<\/a>, when much of Europe was covered by ice, new fossil evidence suggests.<\/p>\n Clues that this hot spring oasis existed include fossilized leaf fragments<\/a>, wood and pollen from temperate, or \u201cwarmth-loving,\u201d species, including oaks<\/a>, lindens and ashes. Such trees were thought to have survived the final phase of the last ice age, called the last glacial maximum (LGM), only in the relatively warm Mediterranean Basin.<\/p>\n But radiocarbon dating shows that many of the newly discovered fossils from the Vienna Basin region of the Czech Republic date to between 26,000 and 19,000 years ago\u2014the height of the LGM. The researchers also found signs of hydrothermal activity in the area at that time. This suggests that geothermal heat<\/a> reached the tree roots in water from hot springs and likely kept those trees alive over thousands of years in an isolated pocket of warm forest that was hundreds of miles to the north of their Mediterranean cousins.<\/p>\n If you’re enjoying this article, consider supporting our award-winning journalism by subscribing<\/a>. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n Biologists have debated for decades about the existence of glacial refugia, or areas where the climate remained temperate, in northern Europe during the LGM. But \u201cthe precise locations of refugia and their impact on the present-day distribution and diversity of species is still under investigation,\u201d wrote University of Oxford biologists Katherine Willis<\/a> and Robert Whittaker<\/a> in an article in Science<\/i><\/a> in 2000.<\/p>\n The genetics of most warmth-loving trees in modern Europe don\u2019t completely correspond to their Mediterranean strains, which suggests that such refugia must have existed where genetically different trees of those species survived. But this is the first time that one has been found.<\/p>\n \u201cAs far as we know, this is the first macrofossil-based evidence of temperate tree species<\/a> dated to the LGM,\u201d says Jan Ho\u0161ek<\/a> of the Czech Geological Survey, a geoarchaeologist and lead author of the paper that described the research, which was published on Friday<\/a> in the journal Science Advances.<\/i><\/p>\n Today the Vienna Basin, where the fossils were found, boasts several freshwater springs with unheated water. But the researchers think that long ago the weight of thick glaciers on the nearby Alps may have triggered tectonic activity that released geothermally heated water from deep in our planet\u2019s crust.<\/p>\n Supporting that idea, the fossilized tree remains were found within buried samples of the mineral geyserite<\/a>, or \u201csilica sinter\u201d\u2014a type of sediment that is typically found around hot springs and geysers\u2014which results when silicon dioxide from rocks dissolves in warm water.<\/p>\n Within the mineral samples, the researcher also discovered distinctive varieties, or isotopes, of oxygen that depend on warm water to form. They indicate the hot springs were typically between 68 and 95 degrees Fahrenheit (between 20 and 35 degrees Celsius), Ho\u0161ek says.<\/p>\n The resulting \u201chot spring oasis\u201d may have covered an area of up to 20 square miles (50 square kilometers) where trees thrived during an ice age, he says. But it probably wasn\u2019t large enough for any large animals or humans to have survived there. And there is no sign that they did, although such refugia must have been attractive places for animals throughout the last glacial maximum.<\/p>\n \u201cSkeletal remains are unfortunately very rarely preserved in this type of sediment,\u201d Ho\u0161ek says. \u201cDespite the fact that the area north of the Alps was very sparsely populated\u2014or even not at all\u2014during the LGM, we hope to find some evidence of such kind in future research.\u201d<\/p>\n![\"Trees](\"https:\/\/static.scientificamerican.com\/dam\/m\/3a94982071c8de44\/original\/ado6611_Fig-1.jpg?w=600\")
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