concept

Density dependence

When a population's growth rate adjusts to its own crowding - breeding fast when sparse, slowing as it packs in, because food runs short, disease spreads and competition bites. This is the restoring force the toy model lacked: it turns fragile, easily-shattered orbits into a true balance the system returns to after a shock, the way a marble rolls back to the bottom of a bowl. A forest stays full because it is built, at every level, to pull itself back toward balance.