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Increasing Atmospheric CO 2 Does Not Increase Global Net Primary Production

Increasing Atmospheric CO 2 Does Not Increase Global Net Primary Production. Group A15 Corinne Benton Nathan Corbin James Parker. Introduction. Net Primary Production: quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass (Zhao & Running 2010)

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Increasing Atmospheric CO 2 Does Not Increase Global Net Primary Production

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  1. Increasing Atmospheric CO2 Does Not Increase Global Net Primary Production Group A15 Corinne Benton Nathan Corbin James Parker

  2. Introduction • Net Primary Production: quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass (Zhao & Running 2010) • NPP = Photosynthesis - Respiration (Freeman 2011) • Could CO2 increase NPP? • Does CO2 increase NPP in reality? • Temperature increases due to increased CO2 levels lead to droughts (Zhao & Running 2010) • Nitrogen is a limiting factor (Reich & Hobbie 2012) • Human food supply depends on NPP

  3. Global NPP Trends • NPP had low variation with a slight decrease for past 30 years (Running 2012) • 53.6 Pg C with ~1 Pg C/year interannual variability • Substantial Carbon increase in atmosphere over past 10 years (Zhao & Running 2010) • Losing 0.38 Pg C per decade to increasing autotrophic respiration • Nitrogen availability limits NPP (Reich & Hobbie 2012) • NPP negatively correlates to drought (Zhao & Running 2010) Image Credit: Reich & Hobbie 2012

  4. Global NPP from 2000-2009 Image Credit: Zhao & Running 2010

  5. NPP for Human Use • NPP Availability (Running 2012) • Inaccessible: 53% • Roots • Preserves • Inaccessible areas • In Use: 37% • Available: 10% • Human population expected to grow by 40% by 2050 (Running 2012) Image Credit: Running 2012

  6. Discussion • CO2 causes higher temperatures • Droughts are caused by higher temperatures • Increase in autotrophic respiration is caused by higher temperatures • Planetary boundaries: • Nitrogen • Phosphorous • Water • Land • NPP limited by many other factors

  7. Discussion • NPP increases linearly while human population increases exponentially • NPP nearing global boundaries • NPP limitations may cause global food shortages

  8. Conclusion Increases in atmospheric CO2 will have little positive impact on global net primary productivity, which implies that human population growth will far outpace NPP growth.

  9. Works Cited • Maosheng Zhao and Steven W. Running, 2010. Drought-Induced Reduction in Global Terrestrial Net Primary Production from 2000 Through 2009. Science 329 (5994), 940-943. [DOI:10.1126/science.1192666] • Steven W. Running, 2012. A Measurable Planetary Boundary for the Biosphere. Science 337 (6101), 1458-1459. [DOI:10.1126/science.1227620] • Peter B. Reich and Sarah E. Hobbie, 2012. Decade-long soil nitrogen constraint on the CO2 fertilization of plant biomass. Nature Climate Change  doi:10.1038/nclimate1694 published online 30 Sep 2012 • Freeman, S. (2011). Biological science. (4 ed.). San Francisco: Pearson Benjamin Cummings.

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