Regime Shifts : Doctoral Essay

Regime shifts are large, abrupt, persistent changes in the structure and function of a system(Biggs et al. 2009). A regime is a characteristic behavior of a system which is maintained bymutually reinforced processes or feedbacks. Regimes are considered persistent relative to thetime period over which the shift occurs. The change of regimes, or a regime shift, usually occurswhen a gradual change in an internal process (feedback) or a single disturbance (externalshocks) triggers a completely different system behavior (Scheffer et al. 2001, Beisner et al.2003, Scheffer and Carpenter 2003, Folke et al. 2004). Although such non-linear change havebeen widely studied in different disciplines ranging from atoms to climate dynamics(Feudel2008); regime shifts have gained importance in ecology because they can substantially alter theflow of ecosystem services to societies (Millennium Ecosystem Assessment 2005, Biggs et al.2009); such as provision of food, clean water or climate regulation. Moreover, the frequency ofregime shifts is expected to increase as human domination on the Earth’s processes continuesto expand -the anthropocene-, modifying climate, biogeochemical cycles, land cover, andspecies distribution (Steffen et al. 2007, Rockström et al. 2009).