Australia: The Land Where Time Began

A biography of the Australian continent 

Pleistocene Megafauna Extinctions – Legacy on Nutrient Availability in Amazonia

According to Doughty, Wolf & Malhi 97 genera of large animals went extinct in the Late Pleistocene, concentrated in the Americas and Australia (Barnosky et al., 2004). There were significant consequences of these extinctions on the structure of ecosystems (Gill et al., 2009), seed dispersal (Janzen & Martin, 1982) and albedo of the land surface (Doughty, Wolf & Field, 2010). However, the impact of these dramatic extinctions on the nutrient biogeochemistry of ecosystems with regard to the lateral transport of dung and bodies has never been explored. In this study Doughty, Wolf & Malhi used a novel mathematical framework that analyses lateral transport as a process that is diffusion-like, and they suggest they have demonstrated the disproportionally large role of large animals in the horizontal transport of nutrients across landscapes. An example they give is their estimate that the Amazonian megafauna extinction decreased the lateral flux of phosphorus, a limiting nutrient, by more than 98 %, with similar, though less extreme decreases in all continents outside Africa. The result of this was a strong decrease in the availability of phosphorus in eastern Amazonia away from the fertile floodplains, and they suggest this decline may still be continuing. The limitation of phosphorus in the Amazon Basin of the present is suggested to possibly be, at least partially, a relic of an ecosystem that lacks the functional connectivity it had in the past. Doughty, Wolf & Malhi argue that the megafauna extinctions of the Pleistocene have resulted in large disruptions in terrestrial biogeochemical cycling on continental scales and increased nutrient heterogeneity globally, that are ongoing.

Sources & Further reading

1. Doughty, C. E., A. Wolf and Y. Malhi (2013). "The legacy of the Pleistocene megafauna extinctions on nutrient availability in Amazonia." Nature Geosci 6(9): 761-764.