CO2 fertilization effect
[2][3] The carbon fertilization effect varies depending on plant species, air and soil temperature, and availability of water and nutrients.
[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.
[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.
Plants will first use their available resources for survival and support the growth and maintenance of the most important tissues like leaves and fine roots which have short lives.
[30] Plants experiencing higher CO2 concentrations may benefit from a greater ability to gain nutrients from mycorrhizal fungi in the sugar-for-nutrients transaction.
[33] The result was that the rate at which CO2 accumulates in the atmosphere did not increase during this time period, although previously, it had grown considerably in concert with growing greenhouse gas emissions.
[33] A 1993 review of scientific greenhouse studies found that a doubling of CO2 concentration would stimulate the growth of 156 different plant species by an average of 37%.
[34][35] In addition to greenhouse studies, field and satellite measurements attempt to understand the effect of increased CO2 in more natural environments.
In free-air carbon dioxide enrichment (FACE) experiments plants are grown in field plots and the CO2 concentration of the surrounding air is artificially elevated.
Open-air chambers have been similarly doubted, with some critiques attributing, e.g., a decline in mineral concentrations found in these CO2-enrichment experiments to constraints put on the root system.
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.
[52]: 439 [53] The nutritional quality of C3 plants (e.g. wheat, oats, rice) is especially at risk: lower levels of protein as well as minerals (for example zinc and iron) are expected.
[56] The effect of increased levels of atmospheric carbon dioxide on the nutritional quality of plants is not limited only to the above-mentioned crop categories and nutrients.
A 2014 meta-analysis has shown that crops and wild plants exposed to elevated carbon dioxide levels at various latitudes have lower density of several minerals such as magnesium, iron, zinc, and potassium.
[50] Declines in magnesium, calcium, potassium, iron, zinc and other minerals in crops can worsen the quality of human nutrition.
Some two billion people live in countries where citizens receive more than 60 per cent of their zinc or iron from these types of crops.
