Tipping Points

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Tompkins Weekly     11-21-16

By Richard W. Franke

Here is a thought experiment. Place a full glass of red wine on the table. Push the top of the glass slowly over – at some point the glass will fall suddenly on its own, spill and possibly break. Now it is impossible to get all the wine back into the glass. It may even be impossible to fix the glass to ever be useful again. You pushed it past the tipping point. Other terms sometimes used for tipping point include “threshold effect” and “critical transition.”

Tipping points are points in the behavior of a system in which a sudden, dramatic, or “nonlinear” event occurs. Tipping points are an important element of “systems thinking,” which we are planning to survey over the next several contributions to this essay series.

The tipping point concept appears to have originated in the social sciences. University of Chicago political scientist Morton Grodzins discovered in the 1950s and 1960s that when African Americans became a certain percentage of a previously all white neighborhood, suddenly all the remaining whites would move out. He labeled this sudden “white flight” from a stable situation the “tipping point.” In a 1971 paper called “Dynamic Models of Segregation,” Harvard economist Thomas Schelling developed mathematical models of the phenomenon and in 2008 researchers confirmed quantitatively that such racial tipping points rest between 5% and 20% across a wide range of U.S. cities and that tipping is “prevalent in the suburbs.” They also found that tipping points are higher in neighborhoods where whites display more tolerant racial attitudes. It is unlikely that most whites consciously count percentages and plan to leave a neighborhood when a specific tipping point is reached; they just somehow engage in group behavior at a certain point.

Why are tipping points of concern in sustainability circles? One reason is that passing a tipping point alters the entire makeup of a system and it can with great difficulty or never be put back into a previously stable state. An environmental example comes out of the research of Dutch lake and pond specialist Marten Scheffer. He found that as excess fertilizer runoff accumulates in a pond or lake, gradually the plants die as algae spreads over the surface. “All of a sudden, the ecosystem that keeps the lake clear collapses.” Scheffer then discovered that removing the algae did not bring the back the clear water. He eventually figured out through trial and error that removing all the fish from a pond made possible a comeback because that allowed the pond plants to grow again and to filter the water. In comparing various system collapses and sudden onsets ranging from desertification to asthma attacks, Scheffer and colleagues identified a number of general warning features that a system might be approaching a tipping point. These include flickering – the way a light bulb sometimes does before it burns out – and reduction in internal system variety – the way a patch of dryland displays a single species just before the desert takes over. Generally, systems are thought likely to exhibit unusual, unexpected behavior when they get close to a tipping point. As our knowledge of tipping points increases, scientists may eventually be able to alert humanity with greater assurance and provide a basis for preventive action.

Knowing where we are at with regard to a major tipping point could be essential information. Without this knowledge, it may be possible to overfish a species past a tipping point where that species can never recover its previous population size. This may have happened with some marine species already. In climate change research it is considered possible that the current gradual melting of the arctic ice cap and the subsequent loss of reflectivity – albedo – could reach a point where temperature increases will take on a life of their own – that is, become impossible for humans to stop even if we lower our CO2 emissions. Another example: melting of the Greenland ice shield could become so rapid that large parts of the sheet slide off into the North Atlantic, rapidly raising sea level. It would be impossible to put the ice sheet back. A similar possibility exists for some of the Antarctic ice shelves, a couple of which have already collapsed in recent years.

One important area for tipping point research is biodiversity. The European Union Environment Agency has developed a biodiversity baseline intended to provide a basis for conceptualizing and identifying tipping points:

“A tipping point is defined, for the purposes of the Global Biodiversity Outlook, as a situation in which an ecosystem experiences a shift to a new state, with significant changes to biodiversity and the services to people it underpins, at a regional or global scale. Tipping points also have at least one of the following characteristics:

The change becomes self-perpetuating through so-called positive feedbacks, for example deforestation reduces regional rainfall, which increases fire-risk, which causes forest dieback and further drying.

There is a threshold beyond which an abrupt shift of ecological states occurs, although the threshold point can rarely be predicted with precision.

The changes are long-lasting and hard to reverse.

There is a significant time lag between the pressures driving the change and the appearance of impacts, creating great difficulties in ecological management.”

Richard W. Franke is professor emeritus of anthropology at Montclair State University, a resident of Ecovillage at Ithaca, and a board member and treasurer of Sustainable Tompkins.

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