Fig. 9. Food density in equilibrium, plotted as a function of consumer density. The dashed middle section of the curve corresponds to the unstable breakpoints of the system (the open circles in Figs. 7 and 8). In the range of consumer densities over which this unstable equilibrium exists, the system tends to either of the two alternative stable equilibria, depending on the initial density of the food population relative to the breakpoint (from Scheffer 1997).