Most of the time, changes in ecosystems are incremental and slow, but every now and then a large, unexpected and persistent change occurs, commonly referred to as regime shift. (Biggs et al. 2012) . These shifts affect crucial ecosystem services such as flood regulation and crop production and subsequently have major impacts on human health, economies, and security. For example in the 1990s, Canada’s Newfoundland cod fishery collapsed and affected the livelihoods of 35,000 fishermen and led to a decline of $200 million dollars per annum in revenues.
The Regime Shifts database, curated by the Stockholm Resilience Centre, provides a comprehensive overview of these changes and illustrates their underlying drivers and impacts. Below is a summary of 28 generic regime shift examples (Biggs, R, 2018) .
I used this freely available data to create an interactive map of regime shifts. You can toggle on and off the legend box on the left, and you can hover your mouse over the shifts of interest to explore the name, ecosystem type, summary, and spatial scale of the specific case study. Many of these shifts, especially the hypoxia cases (where oxygen in the water decreases to a level that can no longer support living organisms) have happened periodically over the years. This map hopefully illustrates the breadth of the cases, situates them geographically and illustrates the magnitude and type of this phenomenon at a glance.
How do regime shifts work?
The systems described above like water bodies, forests, food webs, etc, have elements that are linked by feedback loops, that are either balancing or reinforcing. Frequently, the same set of feedbacks of matter and energy dominates the system and leads it to a stable structure. However, in complex systems, depending on the initial conditions and follow-on pressures, it’s possible to have more than one configuration of dominant feedbacks. These alternative stable states -or mathematical attractors- are separated by critical tipping points (Lenton 2013) .
Over time, a certain set of feedback loops will become dominant and will structure the system in a particular way, forming a regime (Biggs et al. 2012), which is a “range of conditions” where the system fluctuates while retaining a similar function. A regime shift happens, when a dominant feedback switches due to nonlinear changes and this leads the system to function in a different way. These switches can be caused by sudden shocks like a hurricane or more gradual shocks like habitat loss, which slowly affect the strength of feedbacks until they reach a tipping point and they change direction.
Let’s take the example of hypertrophic lakes that shift from clear waters full of fish and plants at the bottom to being covered in algae where the plants have died. The first regime (clear water) is the initial basin of attraction where the system state fluctuates. Plants in the bottom of the lake absorb phosphorus, filtrate the water and get nutrients that help them grow hence creating a positive feedback loop that maintains the clear water regime.
Suddenly we might discover an increase in algae due to a sudden shock (i.e. a big rainfall) which results in increased phosphorus concentration into the lake. This overwhelms the feedbacks that maintain the regime described above, it exceeds their capacity to absorb phosphorus and leads to a shift that results in algal blooms. When algal blooms happen they expand and create dense mats which, in turn, absorb even more light from the plants. The plants then die and the feedback loop in completely broken.
The slow erosion of feedbacks usually goes unnoticed until the actual regime shift occurs and it’s frequently costly or impossible to reverse (Scheffer et al. 2001) . In other cases, it may be possible to intervene at the level of key feedbacks or drivers but more research is needed to understand and compare ecosystem types, drivers, feedbacks, and impacts as well as understand how human actions act as both a driver and feedback of regime shifts.
What was striking in Bigg’s paper  is that:
“climate change has been identified as a contributing driver in almost two-thirds of the regime shifts captured to date, and environmental shocks such as droughts and floods are a driver in almost one-half of the recorded regime shifts”.
- Crépin, A.S., Biggs, R., Polasky, S., Troell, M. and De Zeeuw, A., 2012. Regime shifts and management. Ecological Economics, 84, pp.15–22.
- Biggs, R., Peterson, G.D. and Rocha, J.C., 2018. The Regime Shifts Database: a framework for analyzing regime shifts in social-ecological systems.
- Lenton, T., 2013. Tipping elements from a global perspective. In Addressing Tipping Points for a Precarious Future. British Academy.
- Scheffer, M., Carpenter, S., Foley, J.A., Folke, C. and Walker, B., 2001. Catastrophic shifts in ecosystems. Nature, 413(6856), pp.591–596. Vancouver