The Changing Scenery

About 15,000 years ago, toward the end of the last ice age, enough of the world's ocean water was locked up into glacier ice that the Bering Land Bridge still existed.

The actual form of the land surface in Alaska and western Canada has actually changed very little during the past 15,000 years, but its outward appearance has altered radically. The Bering Land Bridge is no longer visible, it having been submerged by water 200 feet deeper than previously. This submersion has now stopped, in fact it stopped about 6,000 years ago. Since then, the shorelines have maintained themselves at approximately their present locations.

And of course the coastal region of southern Alaska and western British Columbia has been largely bared of the extensive glacier ice that covered it during the ice age. Now, deep fjords, broad coastal flats and forested valleys appear where there was only ice before. No people could have lived in this region then.

Even where there was no ice cover in the interior valleys and uplands of Alaska and Yukon Territory, the appearance of the land has changed. Just within the last 15 years, people who study such things have concluded that the vegetation during the ice age was quite different than it is now. Instead of the forests and mossy swamplands we are familiar with, there must have been broad expanses of prairie land largely covered by grasses, sedges and flowers.

Examination of pollens laid down in lakes and other areas at that time show that spruce and alder were lacking, though there were some birch trees. In a recent lecture at the Geophysical Institute, USGS geologist David Hopkins suggested that the ice age summers were comparatively dry. That dryness not only caused a different vegetation cover, it also led to the existence of widespread sand dunes in the valleys of the Yukon River and its tributaries.

Dr. Hopkins noted that this was the time when mammoths, horses, bison and wapiti (American stag or elk) ranged over the countryside. He suggests that these grazing animals might actually have contributed to the maintenance of the open grasslands, for the same reasons that domestic pasture lands are more productive when grazed. By eating grass, animals, like lawnmowers, promote better growth and they also drop fertilizer. Dr. Hopkins noted that the fertilizer left by even one mammoth was not inconsequential, since each ate 200 or more pounds of grass each day.

One interesting point about the ice age climate is that, in some ways, it might have been much like that experienced in interior Alaska the past three years, warm in winter, wet in spring, and dry in summer. Were the weather we have been having these past few years to continue, we could be trending toward more extensive open, dry grassland than now exists. Of course, no one really knows whether the somewhat usual weather of the past few years is just a fluctuation from normal or if it signals the beginning of climatic change. But whatever happens, we will be able to stroll over the countryside without watching each footstep, since we know that the mammoth won't be back.