Large changes in mammalian grazers have occurred
The loss of most of the North American megafauna at the end of the last Glacial Maximum (~11,000 years ago) remains a major unexplained ecological phenomenon (Martin, 1984), as is the establishment of grasslands in what is now tropical forests (Kingdon, 1989). The global turnover of mammalian fauna at the end of the Miocene (6 to 8 million years ago) was the greatest faunal change within the last 30 million years and also remains largely unexplained (Janis, 1993). Traditional explanations include "overkill" by paleoindians for the North American megafauna, aridity related to cooler climates in Glacial conditions, and increasing global aridity at the end of the Miocene (e.g., Webb, et al., 1995), respectively. However, all these phenomena appear to be related to changes in the atmospheric CO2 concentration and to changes in the global distribution of different photosynthetic pathways in plants. Today atmospheric CO2 levels are changing at unprecedented rates and approaching values not seen for a million years or more. We believe that to understand the historical and future changes in global ecology, we must bring together ecology, plant physiology, animal physiology, vertebrate paleontology, and isotope geochemistry to bear on this common problem. Our research melds field and laboratory studies of modern and paleoecosystems. This research also provides a unique opportunity for public outreach and undergraduate training on topics of broad interest to society and to the future of humankind.

Janis CM (1993) Ann. Rev. Ecol. Syst. 24: 467-500.

Kingdon J (1989) Island Africa. Princeton University Press.

Martin PS (1984) Quaternerary Extinctions: A Prehistoric Revolution. University of Arizona Press, Tucson.

Webb SD et al. (1995) In: Paleoclimate and Evolution. (Vrba E et al., Eds.)Yale University Press, p. 91-108.