NEWS 2019-05-11

Contagious collapses

New study reveals hidden links and potential domino effects between tipping points in climate, ecosystems and societies

Sometimes ecosystems change in so dramatic and substantial ways that they cross a “tipping point”. Scientists call such largely irreversible changes “regime shifts”. One example is how a rainforest can shift abruptly to dry savannah due to the combined effect of deforestation and climate change.

Now a group of researchers from Stockholm Resilience Centre and the Beijer Institute has teamed up with Beijer Fellow and Princeton University ecologist Simon Levin to study how such regime shifts can be better managed and prepared for. Their results, published in Science, suggest that more attention should be paid to how regime shifts are connected and how those connections could be managed.
“Regime shifts pose challenges to ecological management and governance because they are difficult to predict and reverse and substantially alter the availability of benefits that people receive from nature,” explains Juan Rocha lead author of the new study.The group of researchers, has specifically studied the potential for some regime shifts to trigger or increase the risk of other regime shifts occurring, so called “cascading” regime shifts. One such example is the connection between Arctic ice sheets and boreal forests, which amplifies each other. When the ice sheets melt, the reflection of the sun’s heat diminishes so the temperature of the planet rises. This increases the risks of forest fires, which discharge carbon into the air that adds to the greenhouse effect, melting more ice.

Hundreds of case studies
The study is based on a systematic network analysis of more than 300 case studies and 30 types of regime shifts, which have previously been collected in the Regime Shifts Database.
The researchers divided the regime shifts into two different types of cascading effects “domino effects” and “hidden feedbacks”. The first type is rather straight forward and occurs when one regime shift gives rise to subsequent regime shifts in a nearby or distant ecosystem, whereas the other “hidden” type is the result of two-way interactions that cannot be identified by studying one regime shift at the time.
When regime shifts are interconnected over large distances, whoever makes decisions on management is not necessarily the one that has to deal with the impacts. This is for example the case for mechanisms that connect far away ecosystems through climate change, fire, nutrient inputs, or trade.
Moisture recycling is another interesting example. It is both a key underlying factor for the regime shift from rainforest to savannah in the Amazon, but also has the potential to cascade far beyond the forest that depend on moisture recycling as an important water source. In this way, changes in moisture recycling can affect mountain forests in the Andes, nutrient cycling in the ocean by affecting sea surface temperature, and therefore regime shifts in marine food webs.

Avoiding regime shifts
For managers it is of key importance to avoid regime shifts as they can have substantial impacts on human economies and societies and are often difficult and costly to reverse. Developing early warning signals that also take coupled regime shifts into account is therefore urgently required.
Another important aspect put forward in the new study is the need to identify common drivers for several different regime shifts. This could result in management strategies that target specific “bundles of drivers”, increasing the chances to avoid several regime shifts simultaneously.

Reference: Rocha, JC, Peterson, G, Bodin, Ö, and Levin, S. 2018. Cascading regime shifts within and across scales. Science 362 (6421), 1379-1383. DOI: 10.1126/science.aat7850