Productivity Paradox
How did mammoths survive the last glacial age in Beringia?
Mammoths, bison and horses were the most common of many large mammals roaming the cold, arid landscape that existed at the peak of each glaciation. Beringia was drier and colder than today during these periods. How could the landscape support these large grazers?
Painting: George Teichmann
Tundra plants could not support large grazers.
Plant fragments taken from the fossilized teeth of these grazing mammals show that they ate mainly grasses. Today, instead of grasses, the northern tundra is full of low-nutrient plants that produce toxic substances to discourage grazing. Tundra plants grow in soils that stay cold and wet because the underlying permafrost blocks water drainage, and because the insulating mosses on the surface keep the cold in and solar heat out. Tundra plants could never have supported mammoths, bison and horses.
Tundra, Eagle Plains, Yukon. Photo: John Meikle, Government of
Yukon
Inset: Raised tussocks surrounded by heath plants are typical of Yukon tundra,
Peel river plateau. Sedges fom massive systems that hold tussocks above the
saturated ground underlain by permafrost. Photo: John Meikle,
Government of Yukon
The grasslands of colder periods could support large grazers.
At the peak of each glaciation, a portion of Beringia was covered in very dry grasslands known as the "Mammoth Steppe." Clear skies, patches of bare ground and low snow cover allowed more solar energy to warm the soils, causing the permafrost to sink further below the surface. Even though air temperatures were colder, the soils, probably warmer than today, could support grasslands. These vast grasslands, like the one in front of you, were probably similar to the grasslands now found on south-facing slopes around Carmacks.
Grasslands, Kusawa, Yukon. Photo: Juri Peepre, CPAWS-Yukon
Inset: Painting: George Teichmann
Ironically, warmer temperatures have meant colder soils in the Yukon. With a warmer climate, will this trend continue, or will we develop topsoil.