The Taiga Ecosystem
The taiga, or boreal forest, is an ecosystem found across the northern regions of North America and Eurasia. It covers much of Canada and extends down into the northwestern United States. In Europe, Scandinavia and much of Russia is covered with boreal forest. Large cities including Moscow and Toronto are found in the southernmost part of the taiga, but farther north it is mostly unpopulated by humans. The taiga is composed of coniferous trees in an almost continuous belt. Boreal forest grows over areas that were once covered by glaciers and still retain some patchy areas of permafrost. Winter in the taiga is long and harsh, with temperatures dipping as low as -90 degrees Fahrenheit. The winter can last up to six months. The summer season is brief, comprising only about fifty to one hundred frost-free days. The taiga has little annual precipitation, only about fifteen to twenty inches, but its climate is humid because of low evaporation.
Plant Life in the Taiga
Taiga woodland soil is rocky, acidic and low in nutrients. The primary vegetation in the boreal forest is coniferous, needle-leaf trees. In North America, the dominant species of coniferous trees are fir and spruce. In Scandinavia and throughout Russia, the Scots pine is usually dominant. Deciduous trees and shrubs are also common, including alder, birch and aspen.
Coniferous forest is well adapted to difficult growing conditions. Needles remain green year-round, which means that the trees don’t need to expend energy by growing new leaves every year. The needles also limit water loss through transpiration, allowing evergreen trees to stay alive even when the ground is frozen and water from the soil is difficult to come by. The shape of the branches allows snow to slide off rather than build up and cause the branches to break.
Animal Life in the Taiga
The boreal forest is home to a wide variety of animal life, including predatory mammals like lynxes, bobcats, bears, and weasels; small herbivores like snowshoe hares, lemmings, and voles; and large herbivores like elk and moose.
Many birds in the taiga, such as wood warblers, are migratory and leave after the warmer season. Seed-eating birds like finches and omnivores like ravens make their home in the tundra year-round. Animals that live year-round in the taiga must adapt. Some hibernate through the coldest part of the season. Others produce an extra layer of fur or feathers to help them survive. Some animals change color to help them blend in with their snowy surroundings.
Water Pollution in the Taiga
Long ago, the taiga was covered by glaciers. When they receded, they left huge gouges and depressions. When it rains, the depressions fill, and lakes and bogs form. The bogs and ponds are a great breeding ground for insects, which help support the migratory bird populations.
Some areas of the taiga are at risk of deforestation caused by acid rain. Russia has a number of plants which smelt nickel, aluminum and lead. These plants emit chemicals into the atmosphere, which causes acid rain to form. Some rivers in the taiga are also at risk, due to the damage caused by the timber industry. Logs sink and cause flooding. When areas of the forest are cut clear, the topsoil erodes into the rivers and streams.