New research has found that the Bering Land Bridge that stretched between Siberia and Alaska during the Ice Age was much more than a Bering Land Swamp.
The discovery may help explain why some animals, such as birds, easily crossed the land bridge, while others, such as the woolly rhinoceros (Coelodonta antiquitatis), were unable to migrate.
The land bridge, submerged beneath the Bering Strait between Alaska and Russia, was above water from about 36,000 years ago until 11,000 years ago. Scientists thought it may have looked like the grassy, dry plain landscape in Siberia and Alaska at that time — but no one had ever examined the ocean floor where the \”bridge\” once stood.
Last year, researchers led by University of Alaska Fairbanks geologist Sarah Fowle traveled on the research vessel Sikuliaq to extract cores of sediment from the bottom of the Bering Sea. It was the first attempt to reconstruct the ancient landscape and climate of the land bridge.
The researchers presented their results today (Dec. 10) at the annual meeting of the American Geophysical Union (AGU) in Washington, D.C. Instead of grassland, they found a swampy landscape dotted with rivers and also dotted with small lakes.
\”We were looking for many large lakes,\” Fowler said in a statement. \”We actually found evidence of a lot of small lakes and river channels.\”
Lake sediments were evident in the seafloor cores, along with pollen, tiny fossils, ancient DNA and organic matter. The pollen and fossils showed that the landscape had trees and mosses. The researchers also found egg cases of a freshwater crustacean, the water flea (Daphnia).
This swampy environment may have been particularly welcoming to some species, such as birds, but there were also places where there was evidence of migrating large mammals. One site had mammoth DNA. Bison are also known to have migrated from Eurasia to North America during the time the land bridge existed, and horses are known to have migrated from North America to Eurasia.
\”Even though it was mostly floodplains and ponds, grazing animals were nearby, just moving uphill after higher, drier areas,\” Fowler said.
However, the environment may have been less favorable for species that did not commute between continents, such as the woolly rhinoceros (native to Eurasia), the American camel (native to North and Central America), and the short-faced bear (native to North America).
\”The watery, wet landscape may have been a barrier for some species,\” Jenna Hill, a geologist at the U.S. Geological Survey who is also presenting research on the Bering Sea core data at the AGU meeting, said in the statement, \”or a route for species that actually travel by water.\” Further research will be needed to understand the full effect of the environment on migration.