Humans are altering the carbon cycle primarily by burning fossil fuels and through land-use changes such as deforestation. Burning fossil fuels releases large amounts of carbon dioxide (CO2) stored for millions of years into the atmosphere rapidly, contributing to elevated atmospheric CO2 levels and enhanced greenhouse effects. Deforestation releases carbon stored in trees and reduces the Earth's capacity to absorb CO2 due to fewer trees and ecosystems able to perform photosynthesis. These disruptions cause a buildup of carbon in the atmosphere, accelerating global warming and climate change.
How Humans Change the Carbon Cycle
- Fossil Fuel Combustion: Burning coal, oil, and natural gas releases ancient carbon stored underground into the atmosphere as CO2, increasing atmospheric concentrations from about 320 ppm in the 1960s to over 400 ppm today, the highest ever recorded.
- Deforestation and Land-Use Change: Clearing forests for agriculture and urban development releases carbon from trees and soils, while also diminishing natural carbon sinks that absorb CO2. This leads to a net increase in atmospheric carbon.
- Other Human Activities: Cement production emits CO2 from limestone processing, agriculture releases greenhouse gases like methane and nitrous oxide, and consumption patterns across the globe contribute indirectly to CO2 emissions via production and transport.
Impact of These Changes
- The natural balance of carbon cycling between the atmosphere, oceans, and biosphere is disrupted.
- More carbon remains in the atmosphere, enhancing the greenhouse effect and causing global temperatures to rise.
- Ecosystem degradation reduces biodiversity and the resilience of natural carbon sinks.
In summary, human activities increase atmospheric carbon primarily through fossil fuel burning and deforestation, disrupting the carbon cycle and driving climate change.
