Shades of Green: Earth's Forests -- Climate Change

The climate is always changing, and normally it happens slowly enough that it isn't a threat to the survival of forests. At the end of the last ice age, the climate became too warm for beeches, maples, spruce, and other trees to persist in the areas that used to be their habitat. Slowly, often over hundreds of years, they spread northwards into places where it had once been too cold for them to grow. They died out in the southern ends of their range, but new populations were thriving to the north. Trees such as oaks and hickories from more southern areas moved into the habitat vacated by the more cold-tolerant species.

Cities are not only a major source of the pollutants that cause climate change, they are also barriers to the "migration" of forests, blocking trees from spreading to areas where the climate has become more suitable. Photo credit Corel Photo Clipart CD.

Because of human activities, the climate is expected to begin changing more quickly. It may happen too fast for the forests to keep up. Also, because of agriculture and development, it might be harder for forests to migrate as they have done in the past. In many places they are now confined to isolated patches, and if the climate becomes unsuitable for them where they are, they may not be able to spread their seeds far enough away to begin their gradual migration. Not just trees would be confined to their current ranges, but also smaller shrubs, grasses, fungi, and thus the animals that depend on them. Climate change brings other problems along with it, however, such as fires, droughts, and floods.

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