Arctic was once lush and green, and it could be again, new research shows

Imagine not a white, but a green Arctic region, with woody shrubs as far north as the Canadian coast of the North Ocean. This is what the northernmost region of North America looks like about 125,000 years ago, during the last interglacial period, new research from the University of Colorado Boulder finds.

Researchers have analyzed more than 100,000-year-old plant DNA extracted from sediment in the Arctic (the oldest DNA in the more sediment so far analyzed in a publication) and found evidence of a shrub in the North -Canadian ecosystems originate, 400 kilometers further north than its current range.

As the Arctic warms up much faster than anywhere else on the planet in response to climate change, the findings published this week in the United States Proceedings of the National Academy of Sciences, can not only be a glimpse into the past, but also a snapshot of our potential future.

“We have had this very rare view over a certain warm period in the past, probably the last time it was warmer than in the Arctic. This makes it a very useful analogue for what we could expect in the future,” he said. he said. Sarah Crump, who is working as a Ph.D. student in geological sciences and subsequently a postdoctoral researcher at the Institute of Arctic and Alpine Research (INSTAAR).

To get this look back in time, the researchers not only analyzed DNA samples; they first had to travel by ATV and snowmobile to a remote region of the North Pole to collect it and bring it back.

Dwarf birch is an important species in the low Arctic tundra, where slightly longer shrubs (which reach a person’s knees) can grow in an otherwise cold and inhospitable environment. But dwarf birch does not currently survive past the southern part of Baffin Island in the Canadian Arctic. Yet researchers have found that DNA from this plant in the ancient sediment of the lake showed that it grew much further north.

“This is a reasonable difference in the distribution of tundra plants today,” said Crump, currently a postdoctoral fellow in the Paleogenomics Lab at the University of California.

Although there are many potential ecological consequences of the dwarf birch creeping further north, Crump and her colleagues investigated the climate feedback associated with these shrubs covering more in the Arctic. Many climate models do not contain these kinds of changes in vegetation, yet these larger shrubs can protrude above snow in spring and fall, making the earth’s surface dark green instead of white so that it can absorb more heat from the sun.

“It’s a temperature feedback similar to ice loss,” Crump said.

During the last interglacial period, between 116,000 and 125,000 years ago, these plants had thousands of years to adapt and move in response to warmer temperatures. With today’s rapid warming rate, vegetation is unlikely to keep pace, but that does not mean it will not play an important role in affecting everything from permafrost thawing to melting glaciers and sea levels.

“As we reflect on how landscapes will equate to the current warming, it is very important that we take into account how these plant ranges are going to change,” Crump said.

Since the Arctic could easily see a rise of 5 degrees Celsius (9 degrees Fahrenheit) towards pre-industrial levels by 2100, it is the same temperature as in the recent interglacial period, these findings may help us to better understand how we can change landscapes as the Arctic is on course to reach these ancient temperatures again by the end of the century.

Mud or microscope

To get the old DNA they wanted, the researchers could not look at the ocean or the land – they had to look into a lake.

Baffin Island is located on the northeastern side of northern northern Canada, kitty corner to Greenland, in the Nunavut area and the lands of the Qikiqtaani Inuit. It is the largest island in Canada and the fifth largest island in the world, with a mountain range running along the northeastern edge. But these scientists were interested in a small lake, past the mountains and near the coast.

Above the Arctic Circle, the area around this is more typical of a high Arctic tundra, with average annual temperatures below 15 ° F (? 9.5 ° C). In this inhospitable climate, the soil is thin and does not grow much.

But DNA stored in the beds below tells a very different story.

To achieve this valuable resource, Crump and her fellow researchers carefully balanced on cheap inflatable boats in the summer – the only vessels that were enough to take with them – and guarded them on the ice from the lake in the winter. They pierced the thick mud up to ten meters below its surface with long, cylindrical pipes and hammered them deep into the sediment.

The purpose of this dire achievement? To carefully extract a vertical history of ancient plant material then to travel back and forth with the laboratory.

While some of the mud was analyzed in a modern organic geochemistry laboratory in the Sustainability, Energy and Environment Community (SEEC) at CU Boulder, it also had to reach a special laboratory dedicated to decoding ancient DNA, at Curtin University of Perth.

To share their secrets, these mud cores had to travel halfway across the world from the North Pole to Australia.

A local screenshot

When they were in the lab, the scientists had to dress like astronauts and examine the mud in an ultra-clean space to ensure that their own DNA did not contaminate that of any of their hard-earned monsters.

It was a race against the clock.

“Your best chance is to get fresh mud,” Crump said. “Once it’s out of the lake, the DNA will start to break down.”

This is why older samples of the multi-bed in cold rooms do not do the thing.

While other researchers also collect and analyze much older DNA samples of permafrost in the North Pole (which acts like a natural freezer underground), the sediments of the lake are kept cool but not frozen. With fresh mud and more intact DNA, scientists can get a clearer and more detailed picture of the vegetation that used to grow in that immediate environment.

The reconstruction of historical vegetation is mostly done using fossil pollen records, which are well preserved in sediment. But pollen tends to show only the whole picture because it is easily blown by the wind and does not stay in one place.

The new technique used by Crump and her colleagues enabled them to extract plant DNA directly from the sediment, sequence the DNA and deduce which plant species lived there at the time. Instead of a regional image, sedimentary DNA analysis gives researchers a local snapshot of the plant species that lived there at the time.

Now that they have shown that it is possible to extract DNA older than 100,000 years, future possibilities abound.

“This tool is going to be really useful on these longer time scales,” Crump said.

This research also planted the seed to study more than just plants. In the DNA samples of their lake sediment, there are signals from a whole series of organisms that lived in and around the lake.

“We were just starting to scratch the surface of what we could see in previous ecosystems,” Crump said. “We can see the presence of everything from microbes to mammals, and we can get much broader pictures of what ecosystems looked like in the past and how they function.”