ENVI CHP 5

human change in carbon cycle

Altering ecosystems has also contributed to a change in the carbon cycle. Converting forests or grasslands to agriculture replaces long-lived plants with those that live for only one year. In addition, the removal of the crop from the field and frequent tilling of the soil tends to reduce the amount of organic matter in the soil. Thus, agricultural ecosystems do not store carbon as effectively as natural ecosystems. Often the clearing of forests to provide farmland involves the burning of the trees, which contributes carbon dioxide to the atmosphere. Figure 5.30 illustrates the importance of carbon sinks and the effects human activities have on the carbon cycle.