CO2 fertilization effect

The CO₂ fertilization effect or carbon fertilization effect causes an increased rate of photosynthesis while limiting leaf transpiration in plants. Both processes result from increased levels of atmospheric carbon dioxide (CO₂).^[2][3] The carbon fertilization effect varies depending on plant species, air and soil temperature, and availability of water and nutrients.^[4][5] Net primary productivity (NPP) might positively respond to the carbon fertilization effect.^[6] Although, evidence shows that enhanced rates of photosynthesis in plants due to CO₂ fertilization do not directly enhance all plant growth, and thus carbon storage.^[4] The carbon fertilization effect has been reported to be the cause of 44% of gross primary productivity (GPP) increase since the 2000s.^[1] Earth System Models, Land System Models and Dynamic Global Vegetation Models are used to investigate and interpret vegetation trends related to increasing levels of atmospheric CO₂.^[4][7] However, the ecosystem processes associated with the CO₂ fertilization effect remain uncertain and therefore are challenging to model.^[8][9]

Terrestrial ecosystems have reduced atmospheric CO₂ concentrations and have partially mitigated climate change effects.^[10] The response by plants to the carbon fertilization effect is unlikely to significantly reduce atmospheric CO₂ concentration over the next century due to the increasing anthropogenic influences on atmospheric CO₂.^{[3][4][11][12]} Earth's vegetated lands have shown significant greening since the early 1980s^[13] largely due to rising levels of atmospheric CO₂.^{[14][15][16][17]}

Theory predicts the tropics to have the largest uptake due to the carbon fertilization effect, but this has not been observed. The amount of CO₂ uptake from CO₂ fertilization also depends on how forests respond to climate change, and if they are protected from deforestation.^[18]

Changes in atmospheric carbon dioxide may reduce the nutritional quality of some crops, with for instance wheat having less protein and less of some minerals.^{[19]: 439 [20]} Food crops could see a reduction of protein, iron and zinc content in common food crops of 3 to 17%.^[21]