CO2 fertilization effect

The CO
2 fertilization effect or carbon fertilization effect is the increased rate of photosynthesis in plants that results from increased levels of carbon dioxide (CO
2) in the atmosphere. The effect varies depending on the plant species, the temperature, and the availability of water and nutrients.[1] However, enhanced rates of photosynthesis in plants due to CO
2 fertilization are only partially transferred to enhanced plant growth and any hypothesized CO2 fertilization response is unlikely to significantly reduce the human-made increases in atmospheric CO2 concentration over the next century.[2]

Earth's vegetated lands has shown significant greening since the early 1980's[3] largely due to rising levels of atmospheric carbon dioxide.[4][5][6][7]

Studies led by Trevor Keenan from the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) show that, from 2002 to 2014, plants appear to have gone into overdrive, starting to pull more carbon dioxide out of the air than they have done before. The result was that the rate at which carbon dioxide accumulates in the atmosphere did not increase during this time period, although previously, it had grown considerably in concert with growing greenhouse gas emissions. Keenan concluded “Unfortunately, this increase is nowhere near enough to stop climate change.”[8]

Theory predicts the tropics to have the largest uptake due to the CO
2 fertilization effect, but this has not been observed. The amount of CO
2 uptake from CO
2 fertilization also depends on how forests respond to climate change, and if they are protected from deforestation.[9]

Free-Air CO2 Enrichment (FACE) experiments
Main article: Free-air concentration enrichment

The ORNL conducted FACE experiments where CO
2 levels were increased above ambient levels in forest stands.[10] These experiments showed:[11]

  • Increased root production stimulated by increased CO
    2    , resulting in more soil carbon.
  • An initial increase of net primary productivity, which was not sustained.
  • Faster decline in nitrogen availability in increased CO
    2     forest plots.
  • Change in plant community structure, with minimal change in microbial community structure.[12]
  • Enhanced CO
    2     cannot significantly increase the leaf carrying capacity or leaf area index of an area.[12]

FACE experiments have been criticized as not being representative of the entire globe. These experiments were not meant to be extrapolated globally. Similar experiments are being conducted in other regions such as in the Amazon rainforest in Brazil.[13]

Decreases in minerals and impacts on human nutrition

Empirical evidence shows that increasing levels of CO
2 result in lower concentrations of many minerals in plants tissues. Doubling CO
2 levels results in an 8% decline, on average, in the concentration of minerals.[14] Declines in magnesium, calcium, potassium, iron, zinc and other minerals in crops can worsen the quality of human nutrition. Researchers report that the CO
2 levels expected in the second half of this century will likely reduce the levels of zinc, iron, and protein in wheat, rice, peas, and soybeans. Some two billion people live in countries where citizens receive more than 60 percent of their zinc or iron from these types of crops. Deficiencies of these nutrients already cause an estimated loss of 63 million life-years annually.[15][16]

References
  1. Cartwright, Jon (Aug 16, 2013). "How does carbon fertilization affect crop yield?". environmentalresearchweb. Environmental Research Letters. Archived from the original on 27 June 2018. Retrieved 3 October 2016.
  2. Kirschbaum, Miko U. F. (2011-01-01). "Does Enhanced Photosynthesis Enhance Growth? Lessons Learned from CO2 Enrichment Studies". Plant Physiology. 155 (1): 117–124. doi:10.1104/pp.110.166819. ISSN 0032-0889. PMC 3075783. PMID 21088226.
  3. "Global Green Up Slows Warming". earthobservatory.nasa.gov. 2020-02-18. Retrieved 2020-12-27.
  4. Tabor, Abigail (2019-02-08). "Human Activity in China and India Dominates the Greening of Earth". NASA. Retrieved 2020-12-27.
  5. Zhu, Zaichun; Piao, Shilong; Myneni, Ranga B.; Huang, Mengtian; Zeng, Zhenzhong; Canadell, Josep G.; Ciais, Philippe; Sitch, Stephen; Friedlingstein, Pierre (2016-08-01). "Greening of the Earth and its drivers". Nature Climate Change. 6 (8): 791–795. Bibcode:2016NatCC...6..791Z. doi:10.1038/nclimate3004.
  6. Hille, Karl (2016-04-25). "Carbon Dioxide Fertilization Greening Earth, Study Finds". NASA. Retrieved 2020-12-27.
  7. "If you're looking for good news about climate change, this is about the best there is right now". Washington Post. Retrieved 2016-11-11.
  8. Krotz, Dan (2016-11-08). "Study: Carbon-Hungry Plants Impede Growth Rate of Atmospheric CO2 | Berkeley Lab". News Center. Retrieved 2016-11-11.
  9. Schimel, David; Stephens, Britton B.; Fisher, Joshua B. (2015). "Effect of increasing CO2on the terrestrial carbon cycle". Proceedings of the National Academy of Sciences. 112 (2): 436–441. Bibcode:2015PNAS..112..436S. doi:10.1073/pnas.1407302112. ISSN 0027-8424. PMC 4299228. PMID 25548156.
  10. "Oak Ridge Experiment on CO2 Enrichment of Sweetgum: Experimental design". ORNL. Jun 29, 2009. Retrieved Nov 23, 2019.
  11. Norby, Richard. "Free-Air CO2 Enrichment (FACE)". ORNL. Retrieved Nov 23, 2019.
  12. Norby, Richard J.; Zak, Donald R. (2011). "Ecological Lessons from Free-Air CO2 Enrichment (FACE) Experiments". Annual Review of Ecology, Evolution, and Systematics. 42 (1): 181–203. doi:10.1146/annurev-ecolsys-102209-144647. ISSN 1543-592X. S2CID 85977324.
  13. "Amazon FACE Experiment". Mar 28, 2015. ORNL. Retrieved Nov 23, 2019.
  14. Loladze, I (2014). "Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition". eLife. 3: e02245. doi:10.7554/elife.02245. PMC 4034684. PMID 24867639.
  15. Taub, D. R.; Miller, B.; Allen, H. (2008). "Effects of elevated CO2 on the protein concentration of food crops: a meta‐analysis". Global Change Biology. 14 (3): 565–575. Bibcode:2008GCBio..14..565T. doi:10.1111/j.1365-2486.2007.01511.x.
  16. Myers, Samuel S.; Zanobetti, Antonella; Kloog, Itai; Huybers, Peter; Leakey, Andrew D. B.; Bloom, Arnold J.; Carlisle, Eli; Dietterich, Lee H.; Fitzgerald, Glenn (2014-06-05). "Increasing CO2 threatens human nutrition". Nature. 510 (7503): 139–142. Bibcode:2014Natur.510..139M. doi:10.1038/nature13179. ISSN 0028-0836. PMC 4810679. PMID 24805231.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.