Fires and megafauna: the answer is in the dung
We recently proposed (Aug/2009) that “The spread of humans, perhaps concomitant with climatic changes, contributed to the mass disappearance of megafauna such as mammoths and other large herbivores (i.e., the Pleistocene-Holocene extinction); this extinction would also have resulted in fuel buildup and the consequent change in fire activity, as suggested by the contemporary effects of megaherbivores.” (Pausas & Keeley 2009; see also Flannery 1994).
Today (20/Nov/2009), in a paper in Science, Gill et al. demonstrate this link between megafauna extinction and fire activity by studying the fossils spores of a coprophilous fungi (Sporormiella) from a lake sediments in Indiana, North America, together with charcoal and pollen from the same sediments (ca. 14,000 years of history). Sporormiella produced spores in the dung of large herbivores, and the amount of spores can be considered an index of the abundance (or biomass) of herbivores vertebrates. The authors demonstrate that the decline in megafauna is associated to an increased fire activity. This also make us to think about the idea of Pleistocene rewilding (Donland et al. 2005) for fuel control and fire reduction.
These papers and other recent ones are putting fire ecology in the front-line of ecology as they demonstrate the strong influence of fire in shaping nature; they emphasize the importance of fire for understanding present, past and future ecosystems as well as global processes. For instance, Nevle & Bird (2008) recently demonstrated that the massive reduction of American natives by the European invasion of America, drastically reduced fire activity and the consequent increase in forest (carbon sequestration) contributed to the ca 2% global reduction in atmospheric CO2. Despite the importance of fire in the global context, they are still poorly represented in global models (Bowman et al. 2009).
Bowman D.M.J.S. et al. (2009). Fire in the Earth System. Science, 324, 481-484.
Donlan C.J. et al. (2006). Pleistocene Rewilding: an optimistic agenda for 21st century conservation. The American Naturalist 168: 660-681
Flannery T. (1994). The Future Eaters: An Ecological History of the Australasian Lands and People. Reed Press, Port Melbourne, Australia.
Gill JL et al. (2009). Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America. Science 326: 1100-1103.
Nevle R.J. & Bird D.K. (2008). Effects of syn-pandemic fire reduction and reforestation in the tropical Americas on atmospheric CO2 during European conquest. Palaeogeography, Palaeoclimatology, Palaeoecology 264: 25-38.