Given time, natural, undisturbed ecosystems theoretically reach a state of dynamic
equilibrium or steady state. Regulatory mechanisms (checks and balances) counter changes within and outside the ecosystem to maintain the steady state. However, since
each ecosystem has developed under a different set of variables, each has a different
capacity to resist stresses and to recover. In addition, humans often upset regulatory
mechanisms, so response may be distorted. When ecosystems are exposed to stress,
some responses may be immediate and others delayed, perhaps for decades. So, to
manage ecosystems effectively it is necessary to know longer-term behaviour as well
as short-term response. This means that palaeoecology and historical records have a
part to play, as has long-term monitoring.