First, the earth has a limited amount of fossil fuels (such as the coal, oil, and natural gas mentioned above) for humans to use. Since they were all created during the Carboniferous period (which occurred about 300 million years ago). There is only a limited amount of fossil fuels. Once they're gone, they're gone. Some geological researchers believe that we are nearing the "halfway point" in extracting these fossil fuels; after which production will be in constant decline.

Second, the consumption of these fossil fuels by burning causes the release of carbon dioxide (CO2), which has been shown by many environmental scientists to contribute to a decline in air quality; as well as to global warming. The measure of the amount of CO2 produced by an individual, event, or business is known as its "carbon footprint", and is a common way to measure overall energy consumption. The larger the carbon footprint; the more fossil fuels burned.

Because of growing concern over global warming, we're starting to pay a lot more attention to ways to decrease our carbon footprints. The easiest way for individuals to do so is to conserve energy. Conserving energy can be accomplished in any number of small and easy ways, like saving gasoline use by walking, biking, or taking any means of mass transit; turning off unused lights and appliances; and by recycling whenever possible, therefore reducing the need for more energy consumption by the creation of new things.

Larger entities like businesses and the government are focusing on decreasing their carbon footprints by investing in "alternative" sources of energy such as wind and solar power. By tapping these renewable resources, we hope not to have to rely solely on fossil fuels anymore.