The question of whether or not carbon dioxide (CO2) is bad for the planet is a complex one. CO2 is a natural result of life and a vital part of the growth cycle of plants. However, an excess of CO2 probably causes climate change, altering Earth's ecological balance and threatening most living things. If humanity cannot reduce its CO2 output, the planet faces an uncertain future.
The Carbon Cycle
Under normal circumstances, CO2 is a natural part of the life cycle on Earth. Animals and humans exhale CO2, and plants absorb the gas and produce oxygen. Carbon passes between the air, land and sea as plants and animals live and die. In the past, this cycle remained balanced, with carbon outputs and carbon absorption running relatively even.
The Industrial Revolution changed that balance. Carbon dioxide produced by burning fossil fuels for heat, transportation and manufacturing has upset this balance. Now, an imbalanced carbon cycle threatens to alter climates and change how we use the land and where we live.
When living things die, the carbon in their bodies returns to the earth. Through millions of years, heat and pressure change this carbon residue of dead plants and animals into natural gas, coal and petroleum. Since the Industrial Revolution, humans have been releasing CO2 from these fuels more quickly than it can be re-absorbed naturally into the carbon cycle. The result: higher levels of CO2 in the atmosphere. According to the U.S. Environmental Protection Agency (EPA), the amount of CO2 in the atmosphere has gone up by 40 percent since 1750. As the amount of CO2 in the atmosphere increases, it can trigger significant changes in climate.
The Greenhouse Effect
The major threat from increased CO2 in the atmosphere is the greenhouse effect. CO2 is a greenhouse gas. It traps the sun's energy as it strikes the earth, warming the atmosphere. An increase in CO2 can increase temperatures further, causing changes in weather patterns.
According to the EPA, humans release 30 billion tons of CO2 into the atmosphere every year. Because each CO2 molecule might last for up to 200 years, this carbon overload can have long-term consequences.
The increase in CO2 in the atmosphere has many side effects. Because plants absorb CO2 as part of their growth cycle, an increase in the gas can cause growth changes in plants. A 2008 study by University of Illinois scientists found that soybeans grown in a high-CO2 environment were more vulnerable to pests. A study by Southwestern University suggests that increased CO2 reduces the protein content of many crops. In addition, high CO2 levels in the oceans can affect the growth of some marine life, making some species more vulnerable to predators.