Beringia

Beringia was a massive prehistoric geographical region that once linked Asia and North America.

This area was much more than a simple crossing. It was a vast territory bounded by the Lena River in Russia and the Mackenzie River in Canada. To the north, it reached the 72° north latitude in the Chukchi Sea. To the south, it was defined by the tip of the Kamchatka Peninsula. At its largest extent, this land bridge covered an area as big as British Columbia and Alberta combined. This massive space allowed for biological dispersal, meaning plants and animals could move between continents.

The creation of Beringia was driven by global climate changes. During the Pleistocene epoch, the Earth experienced periods of intense cooling. This cooling caused the expansion of massive glaciers across North America and Europe. As these giant ice sheets grew, they trapped enormous amounts of the Earth's water. This process caused global sea levels to drop significantly. When the sea level fell, the shallow ocean floor became exposed land. This exposed terrain formed the Bering land bridge. Today, the average depth of the Bering Strait is only about 50 meters. This means the land bridge appeared whenever the sea level was more than 50 meters lower than it is now.

Scientists have spent decades reconstructing how this landscape changed over time. In the late 19th century, researchers found remains of Late Pleistocene mammals on the Aleutian Islands. This suggested a land connection once existed beneath the Bering Sea. In 1937, Eric Hultén proposed that tundra plants had spread across a submerged plain. He named the region Beringia after Vitus Bering, who sailed the strait in 1728. Later, American geologist David Hopkins expanded the definition of Beringia. He included more of Alaska and Northeast Asia in the region. His work helped scientists understand Beringia as a complex biological zone rather than just a path.

Beringia served as a unique ecological refugium for many species. A refugium is a place where living things can survive even when their wider environment becomes harsh. During the last glacial period, much of the world was covered by a dry mammoth steppe. However, Beringia received moisture and cloud cover from the North Pacific Ocean.

This moisture created a shrub-tundra habitat. This environment was much more productive than the dry areas nearby. It supported a highly diverse community of megafauna, which are very large animals. Because of this, the plants and animals of Beringia were often more similar to those in Eurasia than to those in North America.

The climate within Beringia was not the same everywhere. It was a mosaic of different biological communities. For example, western Beringia in Siberia was colder and drier than eastern Beringia in Alaska and the Yukon. In eastern Beringia, the environment was more ecologically diverse. Around 22,000 years before present (YBP), the average summer temperature was much cooler than today. On the Seward Peninsula, temperatures were much colder than in the Yukon. Despite this cold, the area supported various plants. These included grasses, herbs, and even isolated forests of larch, spruce, birch, and alder.

Human and animal migrations were deeply tied to these shifting landscapes. It is believed that a small human population, perhaps only a few thousand people, arrived from eastern Siberia. They likely moved into the Americas during the Last Glacial Maximum. They expanded into the Americas as American glaciers began to melt, but before the land bridge was flooded.

Many animals also used this corridor. As the climate warmed after 14,500 YBP, new habitats allowed species to spread. Some animals moved into northern Asia, while others moved into North America. However, as the Holocene sea level rose, the bridge was finally inundated around 11,000 YBP. This rising water closed the land connection and reopened the Bering Strait.

Beringia's history shows how much the Earth's systems are connected. The movement of ice, the level of the sea, and the migration of life are all part of one story. Even though the land bridge is now mostly underwater, its impact remains. It shaped the distribution of species across two continents. Today, only a few pieces of this former world remain visible above the water. These include the Diomede Islands, the Pribilof Islands, St. Lawrence Island, St. Matthew Island, and King Island.