Ancient environmental DNA – the earliest-known to date – has been obtained from Ice Age sediment in northern Greenland, shedding light on the biodiversity of a two-million-year-old ecosystem, and helping scientists to predict the long-term ecological toll of present-day global warming.
The DNA fragments – measuring only a few millionths of a millimeter long – were obtained from the Kap København Formation in Peary Land, a 100 metre-thick sediment deposit located at the mouth of the Independence Fjord.
The sediment, which had built-up over the course of 20,000 years with remains of animals and plants, was eventually preserved in permafrost, and remained undisturbed for two millions years until 2006, when a team of researchers visited the Kap København site.
Most of the sediment samples collected there were then stored away for future analysis.
‘It wasn’t until a new generation of DNA extraction and sequencing equipment was developed that we’ve been able to locate and identify extremely small and damaged fragments of DNA in the sediment samples,’ said Professor Kurt Kjær from the University of Copenhagen who, alongside an international team of researchers, assisted in studying the DNA extracts, as discussed in a paper recently published in Nature.
They found that the DNA fragments from Kap København are around one million years older than the earliest-known DNA, which had been recovered from the molar of a Siberian mammoth dated between c.1.2 and 1.1 million years ago.
Each DNA fragment was then compared with extensive libraries of DNA from present-day animals, plants, and microorganisms, in order to build up a picture of Greenland’s ecosystem during the Early Pleistocene.
Analysis identified DNA of the predecessors of present-day reindeer, hares, lemmings, and geese, as well as birch and poplar trees, and marine species including horseshoe crab and green algae.
Mastodon DNA was also detected, revealing that the elephant-like herbivores roamed as far as Greenland before later becoming extinct.
Some DNA fragments, however, could not be linked to species still around today.
The results have revealed that a more diverse, forested habitat existed in the region at this time than previous reconstructions – based on the limited fossil record – had suggested.
During the Early Pleistocene, climates in the polar region were between 10 and 17 degrees Celsius warmer than today, similar to those forecast in the future as a result of global warming.
Assistant Professor Mikkel Pedersen from the Lundbeck Foundation GeoGenetics Centre, and co-author on the study, said: ‘The Kap København ecosystem, which has no present-day equivalent, existed at considerably higher temperatures than we have today – and because, on the face of it, the climate seems to have been similar to the climate we expect on our planet in the future due to global warming.
‘One of the key factors here is to what degree species will be able to adapt to the change in conditions arising from a significant increase in temperature. The data suggests that more species can evolve and adapt to wildly varying temperatures than previously thought. But, crucially, these results show they need time to do this. The speed of today’s global warming means organisms and species do not have that time.’