There has been an extensive effort in recent years to examine the role of regime shifts or sudden changes in system behavior in ecological systems in response to small or slow changes in udnerlying parameters. Several wxamples, such as eutrophciation in lakes, or changes in coral-algal-grazer systems, are prime examples. Much of the effort has been aimed at predicitng an impending regime shfit -- developing an early warning signal.
The idea started from a simple applciation of ideas from the saddle-node bifurcation. I list jsut two references, but there are a very alrge and growing number -- see the references in the Boettiger et al article, which is from a special issue of the journal which contains many more references. THere is also a book by M. Scheffer that is worth reading.