Most of the land mass that encircles the North Pole is covered with an evergreen crown. It is home to the giant northern or boreal forest of Earth. Its remarkable fauna and flora are well adapted to the harsh frigid environment.
The boreal forest is truly immense. It occupies 4.6 million square miles or roughly one-and-a-quarter times the size of either Canada or the U.S.
In North America it stretches from Newfoundland across at least the northern part of every Canadian province and the southern part of the territory and most of Alaska. Across the Bering Strait it covers eastern Siberia and slivers of northern Mongolia and China, and it marches across a vast expanse of Russia eastward into most of Scandinavia.
Evergreen spruce, pine and fir needles’ must endure blasting ice shards and unimaginable freezing temperatures as low as minus 65 degrees. Thick coatings of wax and sunken pores or stomates that absorb CO2 for photosynthesis are but two important needle adaptations enabling these trees to thrive in this environment. Although larches are cone bearing or conifers they are deciduous preferring to grow new needles each spring.
Birches, alders, poplars and willows also make a living in these northern forests. As a matter of fact, European aspen which lives in the boreal forest is the most widespread of all the 80,000 species of trees on Earth.
Incidentally, the northern most tree line is determined by temperature; that is, the average temperature of the warmest month, July, must be greater than 50 degrees.
In North America the boreal forest sits on top of the Canadian Shield, at over 4 billion years old it comprises some of the oldest known rock on the planet.
Lightning-induced fire plays an important role at resetting the biological clock and promoting diversity in the boreal forest. At average intervals of 150 years massive fires char the land. Jack pine cones are sealed shut awaiting the heat of the fire to melt the resin around the cone scales and release millions of seeds to quickly enable re-colonization of the land. Jack pine cones are able to withstand fire temperatures of 1,292 degrees for three minutes.
Wood-hungry beetles attack smoldering trees and immediately assist in decomposing dead wood. Woodpeckers soon follow to feast on these beetles, keeping their numbers in check.
Winter in the boreal forest is magic. I trained as an eco-tree-physiologist specializing in life in the cold and so each time I visit the boreal forest I cannot help but marvel at myriad adaptations of both animals and plants.
For instance, the diminutive muskrat remains active in cold water mostly under ice all winter long. In the fall they increase their blood volume and the amount of oxygen-binding myoglobin in their muscles. They build small winter lodges and create a number of feeding shelters nearby. As ice forms they gnaw through it and cache soggy vegetation under the snow where it freezes. They remember where the cavities are and revisit then to rest and eat throughout the winter.
Three species of chickadees, the smallest birds to reside permanently in the boreal forest, hoard seeds, berries and fossick for hibernating insects, pupae and egg clusters. They must eat every morning or they perish. A large portion of their brain, called the hippocampus, is dedicated to spatial memory. Remarkably, it increases and decreases seasonally.
Voles, mice, lemmings and shrews are also active all winter long on the forest floor underneath a blanket of snow. They gnaw on roots, bark, twigs, shoots and fungi.
The pygmy shrew — aptly named for its size of five grams or the weigh of a quarter — has a voracious appetite. It hunts insects, spiders, mites and must eat every two to three hours as it consumes 80 to 90 percent of its body weight each day. In order to cope with the winter it looses 45 percent of its body weight by shriveling up. Its skull and back-bone shortens, muscles thin out and its liver and spleen become smaller.
Spring peepers, the wood frog and the striped chorus frog have adapted to winter conditions in the far north by deliberately freezing solid with no perceptible heartbeat. As if by magic in the spring they thaw and soon after males in search of females peep over 4,500 times a night.
The onset of spring brings millions of migratory birds to the boreal forest. My favorite are the loons. There’s nothing more ethereal or hypnotic than the call of the loon on a lake. These birds are champion divers and fisherman attaining depths in excess of 266 feet and one record holder dove 201 times in three hours.
The spring also signals the hatch of billions of biting mosquitoes and slashing black-, deer- and horse-flies.
The boreal forest has millions of nutrient-poor stagnant bogs and slow-flowing fens. Sundews, pitcher plants, butterworts and bladderworts or carnivorous plants, live in the bogs and fens and feed on plentiful nutrient-rich bugs.
The effects of global warming are very apparent in the boreal forest. Spruce and mountain pine bark beetles are on a tear and have recently entered the southwestern boreal forest with an endless food supply of Jack pines stretching eastward across the continent. Warming soils are releasing methane, a greenhouse gas 20 times more potent at absorbing heat than CO2, five times faster than computer models predicted. And nighttime summer temperatures have risen so dramatically in the last 10 years that some Alaskan forests have stopped growing.
Essentially the boreal forests have become the modern version of canneries in the coal mines. The boreal forest is obviously extremely sensitive to rising temperatures. We must conserve these exquisite forests and significantly reduce our dependency on coal, petroleum products and natural gas by seeking clean alternative technologies in the coming decade.
Dr. Reese Halter is a conservation biologist at Cal Lutheran University and public speaker. His latest book is “The Incomparable Honeybee”, Rocky Mountain Books. He can be reached through http://www.DrReese.com