human activity has changed the carbon cycle drastically. The amount of
carbon dioxide gas in the atmosphere has increased over 30 percent
since the industrial revolution in 1850.Burning fossil fuels have
reintroduced carbon into the cycle that was removed from it long ago
and stored deep within the earth. So much carbon is released so into
the atmosphere from these activities so quickly, that the natural
carbon cycle cannot move all of it to other stores. Scientists
estimate that carbon stores in the atmosphere might rise by one third
and perhaps as much as 3.4 times by the end of the century.Greenhouse
gases contribute to global warming and carbon dioxide is 1 of the
gases that causes this, which is why it is important to decrease
carbon dioxide emissions.

clearing land for agriculture and the expantion of cities reduces the
total amount of carbon taken from atmosphere by plants during
photosynthesis. farmed plants do remove some carbon from atmosphere
they remove less than natural vegatation.