Abstract
The decline of atmospheric CO2 over the last 65 million years (Ma) resulted in the 'CO2-starvation' of terrestrial ecosystems and led to the widespread distribution of C4 plants, which are less sensitive to CO2 levels than are C3 plants. Global expansion of C4 biomass is recorded in the diets of mammals from Asia, Africa, North America, and South America during the interval from about 8 to 5 Ma. This was accompanied by the most significant Cenozoic faunal turnover on each of these continents, indicating that ecological changes at this time were an important factor in mammalian extinction. Further expansion of tropical C4 biomass in Africa also occurred during the last glacial interval confirming the link between atmospheric CO2 levels and C4 biomass response. Changes in fauna and flora at the end of the Miocene, and between the last glacial and interglacial, have previously been attributed to changes in aridity; however, an alternative explanation for a global expansion of C4 biomass is CO2 starvation of C3 plants when atmospheric CO2 levels dropped below a threshold significant to C3 plants. Aridity may also have been a factor in the expansion of C4 ecosystems but one that was secondary to, and perhaps because of, gradually decreasing CO2 concentrations in the atmosphere. Mammalian evolution in the late Neogene, then, may be related to the CO2 starvation of C3 ecosystems.
Full Text
The Full Text of this article is available as a PDF (843.2 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Andrews P., VanCouvering J. A. Palaeoenvironments in the East African Miocene. Contrib Primatol. 1975;5:62–103. [PubMed] [Google Scholar]
- Ehleringer J. R., Cerling T. E. Atmospheric CO(2) and the ratio of intercellular to ambient CO(2) concentrations in plants. Tree Physiol. 1995 Feb;15(2):105–111. doi: 10.1093/treephys/15.2.105. [DOI] [PubMed] [Google Scholar]
- Freeman K. H., Hayes J. M. Fractionation of carbon isotopes by phytoplankton and estimates of ancient CO2 levels. Global Biogeochem Cycles. 1992 Jun;6(2):185–198. doi: 10.1029/92gb00190. [DOI] [PubMed] [Google Scholar]
- Leakey M. G., Feibel C. S., McDougall I., Walker A. New four-million-year-old hominid species from Kanapoi and Allia Bay, Kenya. Nature. 1995 Aug 17;376(6541):565–571. doi: 10.1038/376565a0. [DOI] [PubMed] [Google Scholar]
- Stute M., Forster M., Frischkorn H., Serejo A., Clark J. F., Schlosser P., Broecker W. S., Bonani G. Cooling of Tropical Brazil (5{degrees}C) During the Last Glacial Maximum. Science. 1995 Jul 21;269(5222):379–383. doi: 10.1126/science.269.5222.379. [DOI] [PubMed] [Google Scholar]
- White T. D., Suwa G., Asfaw B. Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia. Nature. 1994 Sep 22;371(6495):306–312. doi: 10.1038/371306a0. [DOI] [PubMed] [Google Scholar]
- deMenocal P. B. Plio-Pleistocene African climate. Science. 1995 Oct 6;270(5233):53–59. doi: 10.1126/science.270.5233.53. [DOI] [PubMed] [Google Scholar]