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

A serious threat to the world's forest cannot be seen or heard. This silent killer is our changing climate. Recently, due to pollution, the Earth's climate has been warming up. This happens when an excess of carbon dioxide (CO₂), and other "greenhouse gases", like methane, nitrous oxide and chlorofluorocarbons (CFC's) are released into the atmosphere.

The climate has changed drastically over thousands of years in the past, but now with the production of greenhouse gases it is happening much more quickly. It isn't completely understood what the exact effects will be, but weather that is more unpredictable and extreme will probably be one result. Photo by Maya Walters.

These gases are called "greenhouse gases" because, like a greenhouse, they soak up the sun's heat and trap it. This action forms sort of an insulating blanket around the earth, causing the temperature to rise, and creating what is called "global warming".

Humans contribute to the climate change through everyday activities that produce greenhouse gases. The most common greenhouse gas is CO₂, which is made mainly by the burning of fossil fuels. So, whenever oil, coal or natural gases are used for things like transportation, factories, heating and cooling or electricity, they add to the climate problem. Also, clearing land for logging, ranching, agriculture and deforestation all contribute to CO₂ emissions.

Climate change might destroy forests, and destroying forests might cause climate change. Clearing vast amounts of land for enormous commercial farms (Below -- photo by Maya Walters) can lead to soil erosion and other long-term problems that prevent the forest from eventually growing back. Small farms are more ecologically sustainable, but not as economically attractive. (Above -- photo courtesy Naomi Woods)

Another greenhouse gas is methane, which results from the growing of rice, raising cattle and sheep, and by decomposing landfills. Some agricultural and industrial activities produce yet more greenhouse gas, nitrous oxides. Refrigerators, freezers, and air conditioners contain freon, which release CFC's into the atmosphere and cause depletion of the ozone layer. This results in increased exposure to ultraviolet light, which adversely affects plants and animals.

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.

The climate change is affecting our forests worldwide. In Alaska, 20 million trees died when they were infested with the spruce bark beetle. The bugs multiplied more rapidly because of warmer than normal temperatures. Also in the United Sates, the chance of forest fires at Yellowstone National Park is increasing, also because of warmer temperatures. The Galapagos islands suffered from several fires in 1994. In 1997 several unexpected forest fires occurred in England. In Siberia, thawing caused the once frozen ground to turn into a huge mud puddle, in which trees and houses were swallowed up. Destructive forest fires have ravaged Australia's trees. In Africa, Central and South America, Southeast Asia and Australia, the trees have shown an increased growth rate, but they are dying at a younger age.

Many countries are trying to stop global warming by cutting down on activities that produce greenhouse gases, but this poses a problem. For example, current methods of generating electricity create CO₂, the main greenhouse gas. Yet electricity is needed everyday, and everybody uses it. So, alternative ways to produce electricity are being found. In Denmark, the government is sponsoring the building of wind generated power plants. The wind power is relatively inexpensive, effective, and environmentally friendly.

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