Plants, CO2 and photosynthesis in the 21st century

Human activity in the last 200 years has led to a marked increase in the level of CO2 in the atmosphere. Plants sense increases in CO2 levels and initially respond with an increase in photosynthetic rate, which may then slow as the plant adapts. This increase in photosynthetic rate may account in part for the 'disappearance' of an estimated 1.8 gigatons of carbon per year.