been well documented. Such shifts may have serious ecological as well as
economic implications. An important problem in this context is to devise
indicators that can serve as warning signals of decreasing resilience and
hence, proximity to an impending transition. Some of the diagnostic measures
suggested include increase in the recovery time of the system (Ref: Held et
al., 2004, Geophysical Research Letters, Vol. 31, L232207) and an increase
in variance near a transition point (Carpenter et al, 2006, Ecology letters,
Vol. 9, 311-318). In this work, we suggest from studies of models that
asymmetry in the recovery time of the system and asymmetry in the time
series distribution can be used as warning signals for a catastrophic regime
shift. The limitations of various indicators and the conditions under which
they can be useful in real ecological systems will be discussed.
