Catastrophic regime shifts in social- ecological systems Christopher Britton-Foster

Focus Paper: Kinzig AP, Ryan P, Etienne M, Allison H, Elmqvist T, Walker BH (2006) Resilience and regime shifts: assessing cascading effects. Ecology Society 11(1): 23. Supporting Paper: Scheffer M, Carpenter SR (2003) Catastrophic regime shifts in ecosystems: linking theory to observation. Trends Ecol Evol 18: 648–56.

Outline Regimes and resilience What is hysteresis? The cascading effect Case studies Implications for management

Regimes and Resilience Regimes are dynamic, never stable Alternative regimes: two different regimes that could exist under the same external conditions

Regimes and Resilience Resilience: the capacity of a system to absorb changes and disturbance while still retaining the same function Catastrophic regime shift Scheffer & Carpenter 2003

Hysteresis Kinzig et al, 2006

Multiple Thresholds Multiple thresholds Ecological Economic Cultural

The cascading effect Breaching one threshold between alternative regimes can trigger the breaching of multiple other thresholds at different scales Perturbation can be : – Large or Tiny – Slow or Fast Creates a new, resilient regime that is often irreversible

Case studies

Thomas Kleitz Foodsubs.com Causse Méjean, France Fedou becomes less of the cultural identity Farmers move toward timber or Roquefort More grassland fragmentation No more Fedou cheese production Encroaching pine patches

Western Australian Wheatbelt Rising water table Salinization and waterlogging Less arable land Fewer viable farms Fewer native plant patches Rural towns become unviable

Goulburn-Broken Catchment, Australia Mark Edwards Farms become unviable Processing plants close down Irreversible shift away from an agricultural economy Drought Irrigation more expensive

Goulburn-Broken Catchment, Australia Mark Edwards Less arable land Processing plants close down Irreversible shift away from an agricultural economy Heavy rainfall Waterlogging and salinization of soil Fewer viable farms Native plant patches die Less natural regulation of watertable

Madagascar Dry Forests Farmers move to urban centre Rural poverty Cultural protection of sacred forests erodes Less pollination to agricultural fields Even fewer viable farms Increasing aridity

Implications for Natural Resource Management CAS and the Cascading effect: Adaptation drives more change at different scales (positive feedback) Identifying which thresholds are most susceptible to external influences (e.g. climate change) Managing for just one variable = blindness to other critical interactions “Rule of Hand”

Discussion Topics Can natural resource managers be expected to predict the influence of their actions on all of a system’s thresholds? Are speculations about possible regime shifts good enough to base important management decisions on?