Collapse of an ecological network in Ancient Egypt
Justin D. Yeakel, Mathias M. Pires, Lars Rudolf, Nathaniel J. Dominy, Paul L. Koch, Paulo R. Guimarães Jr. and Thilo Gross
PNAS 111, 14472-14477, 2014
The dynamics of ecosystem collapse are fundamental to determining how and why biological communities change through time, as well as the potential effects of extinctions on ecosystems. Here we integrate depictions of mammals from Egyptian antiquity with direct lines of paleontological and archeological evidence to infer local extinctions and community dynamics over a 6000-year span. The unprecedented temporal resolution of this data set enables examination of how the tandem effects of human population growth and climate change can disrupt mammalian communities. We show that the extinctions of mammals in Egypt were nonrandom, and that destabilizing changes in community composition coincided with abrupt aridification events and the attendant collapses of some complex societies. We also show that the roles of species in a community can change over time, and that persistence is predicted by measures of species sensitivity, a function of local dynamic stability. Our study is the first high-resolution analysis of the ecological impacts of environmental change on predator-prey networks over millennial timescales, and sheds light on the historical events that have shaped modern animal communities.
Figure 1: Changes in the dynamic stability of the Egyptian food web over time. Proportion of stable webs (\(3.2 \cdot 10^9\)
replicates) for the Egyptian community (black), and with first and last appearances treated probabilistically, incorporating error of 286 (dark blue, dashed line) and 580 (lighter blue dotted line) years before and after the first and last occurrences. Vertical dashed lines denote the major climatic events at ca. 5050, 4170, and 3035 yrs BP.