How does rising atmospheric CO2 affect marine organisms?

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Pasture and Rangeland
Responses to Elevated CO2

Campbell, B.D., Stafford Smith, D.M., Ash, A.J., Fuhrer, J., Gifford, R.M., Hiernaux, P., Howden, S.M., Jones, M.B., Ludwig, J.A., Manderscheid, R., Morgan, J.A., Newton, P.C.D., Nosberger, J., Owensby, C.E., Soussana, J.F., Tuba, Z. and ZuoZhong, C.  2000.  A synthesis of recent global change research on pasture and rangeland production: reduced uncertainties and their management implications.  Agriculture, Ecosystems and Environment 82: 39-55.

What was done
This paper reviews research work done between 1994 and 1999 by a worldwide network of 83 scientists associated with the Global Change and Terrestrial Ecosystems (GCTE) Pastures and Rangelands Core Research Project 1 (CRP1), which has resulted in the publication of over 165 peer-reviewed scientific journal articles.  It presents a synthesis of knowledge gleaned from key publications of this effort.

What was learned
"Overall," in the words of the authors, "the stimulatory effect of double ambient CO2 on grassland production averages about +17% in ecosystem-based experiments."  They note, however, that the increase would likely be higher "in moisture-limited and warm-season grassland systems."  In addition, they say that "elevated CO2 and reductions in water availability are predicted to increase woodland thickening," and that "growth of C4 species is about as responsive to CO2 concentration as are C3 species when water supply restricts growth, as is usual in grasslands containing C4 species."  Finally, they find that the legume content of grass-legume swards is increased by about 10% due to a doubling of the air's CO2 content.

What it means
The ongoing rise in the air's CO2 content should have a significant positive effect upon pasture and rangeland productivity in the years ahead.  And since this phenomenon appears to slightly augment the legume content of grasslands, extra nitrogen should gradually become available to these entire ecosystems, enabling them to maintain the nutritive quality of their forage.  Future increases in the air's CO2 content should also enable pasture and rangeland plants to better cope with water deficits that will undoubtedly occur periodically; and they should provide an impetus for more woody species to gain a foothold in these areas, as described in several of the Journal Reviews listed under Trees (Range Expansions) in our Subject Index.  In addition, the work of this GCTE research group suggests that the ongoing rise in the air's CO2 content will most likely not result in C3 species out-competing C4 species, as is also suggested by most of the Journal Reviews listed under Biodiversity (C3 Plants vs. C4 Plants) in our Subject Index.