What two recurring events in Earth's history have an impact on the carbon cycle?

Carbon is stored inside plants. When deforestation occurs or any other natural clearing of land, the carbon cycle is changed due to plants being removed that would have captured the CO2 and changed it to oxygen and also by the removal of large plants that store carbon being replaced with either small crops or concrete that do not store carbon. In nature, fossil fuels release carbon very slowly over time, humans burn it at a much greater rate due to dependence on it, and burning fossil fuels emits a lot of CO2 into the atmosphere.