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If any one landscape on Earth has proved more useful to humanity it may be the forests. They have provided lumber for homes and ships, firewood, food, medicines, and a plethora of folk stories and deities.
But forests' usefulness has been their undoing. Many of the world's great forests are either much reduced by logging or on their way. North America's forests once stretched nearly the length of the continent, north to south, and from the Atlantic Ocean to the edge of the Great Plains. Likewise, Ireland and England were heavily wooded islands. You wouldn't know to look at them today. In fact, few places on Earth retain any virgin forests.
Evergreen Ocean
The tsar of all forests on Earth is the taiga. It circles the planet from Sweden to Siberia to Alaska and Canada. It's a cold, evergreen forest that is the largest single terrestrial biological zone on the planet. It's where most of the world's trees live — and it's populated almost entirely by evergreen species.
Taiga is also a vast player in the seasonal changes in carbon dioxide levels in the entire atmosphere. Every spring, the trees awaken and start absorbing carbon dioxide and releasing oxygen. In the fall, the trees shut down and hibernate, and carbon dioxide from an array of sources builds up.
Big as the taiga is, however, it's not able to keep up with the carbon dioxide humans have added to the atmosphere since the dawn of the Coal Age and the Industrial Revolution. Carbon dioxide is, after all, the No. 1 greenhouse gas.
