If you picture the North Sea, you think of rough water, cargo ships, and offshore wind farms. But what if that same patch of ocean once held a walkable woodland, the kind that crunches underfoot with fallen leaves?
A team led by the University of Warwick analyzed ancient sedimentary DNA from 252 seabed samples taken from 41 marine cores and found signs of temperate forest in southern Doggerland more than 16,000 years ago. Published in the Proceedings of the National Academy of Sciences, the study suggests oak, elm, and hazel were established far earlier than many records implied.
It also hints the North Sea may have fully formed later than previously assumed, a timeline shift that could change how researchers think about ecosystems and human movement after the last Ice Age.
Doggerland was not just a shortcut
Doggerland is the name researchers use for the now submerged region that once linked Great Britain to mainland Europe. When sea levels were lower after the last Ice Age, you could walk into what is now eastern England without crossing open water. So the old idea of a “land bridge” starts to feel a little thin.
For years, the big question was timing. When did trees actually take hold there, and could people have lived in those ecosystems rather than simply passing through? The team focused on sediments from an ancient river landscape, often called the Southern River, because those layers can preserve biological traces with unusual clarity.
How seabed mud keeps a biological record
The study relies on ancient sedimentary DNA, often shortened to sedaDNA. Plants and animals shed genetic material into their surroundings, and in the right conditions those fragments can persist in sediments for thousands of years. Compared with pollen records, sedaDNA can give a more local snapshot of what was growing right there.
Lead author Robin Allaby said the team rebuilt Doggerland’s environment “at a scale never seen before” by scanning sedaDNA across southern Doggerland. “Unexpectedly, we have found trees thousands of years older than expected, and evidence that the North Sea formed completely later than was believed,” Allaby said. That is a big claim, and it is exactly why this kind of genetic archive is drawing so much attention.
Oaks and hazels appear earlier than expected
The extracted DNA indicates oak, elm, and hazel were present thousands of years before they show up in some British pollen records. Even linden, the genus Tilia, appears about 2,000 years earlier than recorded elsewhere in Britain. Taken together, the pattern suggests Doggerland may have acted as a northern refuge during colder periods.
That fits the idea of microrefugia, small pockets of habitat that can shelter species through harsh climates. It also connects to Reid’s paradox, the long running puzzle of how forests recolonized northern Europe so quickly after ice retreated. In other words, some trees may not have had to “rush north” at all because a few had already been waiting there.
The study also reports traces of Pterocarya, a walnut relative thought to have disappeared from northwest Europe around 400,000 years ago. If that signal reflects real late survival, it would mean some plant lineages lasted far longer than standard timelines suggest. At the very least, it is a reminder that extinction and range loss can be messy, with holdouts in unexpected places.
Why forests matter for early people
A wooded Doggerland would have offered more than scenery. Forests provide fuel, shelter, edible plants, and habitat for forest animals such as wild boar, creating a richer resource base for human groups. That could have been true long before the better documented Maglemosian culture that appears around 10,300 years ago.
Allaby said the genetic evidence is “the best evidence to date” that Doggerland’s wooded environment “could have sustained early Mesolithic communities” before flooding reshaped the region. He also noted that it may help explain why relatively little early Mesolithic evidence survives in coastal parts of Britain today, since many sites may now lie offshore. It is hard to excavate a campsite that sits under waves.
Vincent Gaffney of the University of Bradford pushed back on the old framing of Doggerland as merely a corridor. “For many years, Doggerland was often described as a land bridge, significant only as a transit route,” he said. In his view, it was “a beating heart of early human settlement,” and it may have served as a refuge for plants and animals that later helped repopulate northern Europe.
A slow drowning, not a single moment
Doggerland’s disappearance was gradual, and the study suggests some parts of the region may have persisted through extraordinary events. The researchers point to flooding episodes that include the Storegga tsunami about 8,150 years ago and they suggest some areas stayed above sea level until roughly 7,000 years ago. So the “lost land” was likely shrinking for generations, not vanishing in an instant.
It is easy to treat coastlines like fixed borders, the way they look on a classroom map. But this research underlines how responsive landscapes are to climate and sea level change, especially after an ice age. If the North Sea fully formed later than previously believed, the timetable for how ecosystems and human routes shifted may need another look.
What a drowned forest teaches a warming world
Microrefugia are not just a prehistoric curiosity. As heat waves and drought strain ecosystems today, small sheltered habitats can help species hang on and spread later, like a shaded creek corridor that stays cool when everything else turns brittle. Conservation planners increasingly pay attention to these “safe spots” because they can buy time.
Doggerland is also a blunt reminder that rising seas do not just redraw shorelines, they can erase lived landscapes. The good news is that sediments can still preserve the story if scientists know where to read it.
The study was published on Proceedings of the National Academy of Sciences.
