Fossil fuels are natural sources of energy formed from the remains of decomposed plants and animals that lived hundreds of millions of years ago. The fuels are buried deep within the earth and harvested by humans for power. More than 70 percent of electricity in the United States is generated from fossil fuels such as coal and oil, according to the Environmental Protection Agency. Conserving fossil fuels and using other forms of energy reap many benefits.

One huge benefit of conserving fossil fuels is that it will save some for future generations. Fossil fuels are nonrenewable resources. About 1 trillion barrels of crude petroleum oil were left in the earth as of 2002, according to Bio Tour. If people continue to use oil at their current rate, the oil will run out by 2043.

Coal is another fossil fuel that should be used conservatively. A recent calculation by Caltech engineers estimates that only 662 billion tons of coal can ever be mined, Wired magazine reports. The previous estimate calculated by the World Energy Council stated that 850 billion tons of coal remained.

Using fossil fuels causes pollution. For example, burning oil and gasoline in cars produces carbon monoxide, a toxic gas. Burning coal produces sulfur dioxide, which causes acid rain that can kill fish, according to the EPA. The EPA also states that asthma is worse in places where outdoor pollution is prevalent.

When accidents happen, many more people, wildlife and ecosystems are devastated. The Deepwater Horizon oil rig explosion in April 2010 in the Gulf of Mexico has killed 658 birds, 279 sea turtles and 36 mammals as of June 2010, according to Boing Boing. It is also causing illnesses in the people who are trying to clean it up and breathing oil fumes. The Huffington Post reported that many fishermen near the oil spill felt drugged, disoriented, fatigued and short of breath.

The pollution generated by burning fossil fuels not only affects local environments, it's also believed to be the main cause of Earth’s climate problem. Climate change is threatening all species of plants and animals who are acclimated to specific temperatures. It is causing rising sea levels, increased temperatures, and major changes in diverse living things that now face extinction.

Carbon dioxide contributes to climate change, and 95 percent of it is from burning fossil fuels, the EPA states. Coal, in particular, is responsible for most of the carbon-dioxide emissions driving climate change, according to Wired. By using fossil fuels more conservatively, you can help reduce the amount of dangerous chemicals in the atmosphere.