Why Cascading Shifts matter for investors

The diversity of drivers presents challenges and opportunities for managing systems with tipping points (Rocha et al., 2015a). On the one hand, understanding common sets of drivers opens the opportunity to manage multiple ecosystems under similar threats. For example, in managing agricultural activities by reducing the use of fertilizers, fishing, and sewage can prevent multiple regime shifts in coastal systems (Rocha et al., 2015b). In fact, recent studies have shown that many of these drivers occur at local to regional scales of management, so people on the ground can do a great deal already to avoid ecological collapses. Climate change, although important, is not the only threat. By reducing pollution, and addressing urbanization or food production related drivers (e.g. fishing, agriculture, use of fertilizers), many tipping points can be avoided, or at least delayed.

The second type of interaction is known as cascading effects (Rocha et al., 2018). Imagine a system, like a forest, tips in one part of the world. How does it affect the risk that other ecosystems tip? If the Amazon tips, are other ecosystems at risk as, for example, commodity producers look for other areas to expand agricultural production? Or the other way around, what ecosystems, if tipped, would increase the risk of the Amazon tipping as well?

The scientific community in general agrees that such cascading effects are plausible. However, most of the studies have been modelling work with a focus on the climate system, thus only focusing on tipping elements that are affected by increases in temperature. Tim Lenton and collaborators suggest that climate tipping elements are interconnected (Lenton et al., 2021), and subsequent modelling work has clarified the mechanisms through which systems such as the Greenland Ice Sheet, the Atlantic Meridional Ocean Circulation (AMOC), the Arctic sea ice or West Antarctica, can be connected (Wonderling et al., 2021).

However, this body of work ignores the living fabric of the planet: the biosphere. Biodiversity in these studies is often seen as a storage of carbon, but less is understood about its role in regulating nutrient cycles, the water cycle, or in producing the benefits people get from nature. Local to regional shifts in ecosystems might not be strong enough to cause detectable effects on the climate system. For example, shifts in coral reefs affect the habitat for a diverse set of species, undermine recreation opportunities, affect fisheries, and increase food insecurity or lead to coastal erosion. But can changes in coral communities impact the climate?

Whether these ecological shifts could amplify or exacerbate climate change is still an open question. Shifts in the frequency of forest fires and forest composition in the boreal forest, could amplify climate change at first, but help capture more carbon in the long term (Mack et al., 2021). Shifts in peatlands and thermokarst lakes can release methane, a strong greenhouse gas that amplifies global warming (Koffi et al 2020). To what extent the biosphere can amplify or dampen climate change is still a key frontier of research.

Our study analyzed 30 different types of abrupt shifts in ecosystems, and found that about 45% of all possible couplings resulted in cascading effects (Rocha et al., 2018). We showed the different mechanisms that exist and could couple ecosystems. While climate change is one, it is not the only one. Yet the empirical evidence to help assess the strength and likelihood of these couplings, is still missing. Focusing only on climate could be misleading, strangely erring on being too optimistic. 

Back to our example of the Amazon rainforest, the temperature threshold is expected in climate models to be reached by 2100s, but the deforestation threshold could be reached in a matter of decades. Fires and current droughts can move the time to tipping even earlier. Similarly, coral reefs can tip already at 2°C, but their probability of recovery is strongly influenced by interaction with other drivers such as fishing pressure, water turbidity, ocean acidification, or the presence of herbivorous fish. Some of these drivers can be managed locally to build resilience against climate change.

A pre-emptive approach that manages the diversity of drivers is imperative. For some of the drivers, local and regional authorities can intervene (e.g., to halt deforestation). We cannot risk crossing arms and wait until the large nations of the world commit to significant actions in reducing emissions and dealing with climate. Opportunities for meaningful actions are available here and now.