Christopher X J. Jensen
Associate Professor, Pratt Institute

System Stability

stability-imageAll sciences are concerned with stability. From subatomic particles to whole galaxies, we seek to understand what makes some phenomena persistent and others fleeting. Nested in the middle of this scale continuum across which stability is considered are the biological sciences. As an ecologist and evolutionary biologist, I can consider system stability across a range of scales: individuals, social groups, populations, communities, and ecosystems are all systems that must remain stable in order to persist.

My dissertation was primarily concerned with system stability: I analyzed the stability properties of different theoretical constructions of simple predator-prey systems, demonstrating ways in which experimental manipulations could compare competing hypotheses. All predator-prey systems are interesting from a stability perspective, because as selection produces more effective predators there is always the potential for prey over-exploitation, which can destabilize the system. The idea that predators exercise “prudent predation” has been rejected as a form of naive group selectionism, but we still do not fully understand what regulates the stability of these fundamental food web links.

I have also been involved in an ongoing research project that considers whether or not predator-prey system destabilization led to the massive extinction of Late Pleistocene megafauna. My collaborators and I have looked at whether the relatively-sudden invasion of technologically-sophisticated human predators may have caused these extinctions in both North America and Australia, essentially by destabilizing the interaction between humans and their larger prey.

My most recent project that includes a consideration of system stability concerns group territorial behavior. Many animals form stable social groups that actively defend territory, but there is no convincing explanation (or set of explanations) that accounts for the stability of these social groups. Through an individual-based simulation, my collaborators and I have been exploring how resource heterogeneity affects the formation and stability of social groups.

As is probably pretty obvious, my interests in cooperation and system stability go hand-in-hand. While not all interesting questions about the stability of biological systems require an explicit consideration of cooperation, understanding stability is crucial to understanding how cooperation evolves. And I would suggest that perhaps if we throw aside the loaded ideas of altruism and selfishness, we can view cooperation as all evolved properties and interactions that foster more complex and stable systems. Using this broader definition of what cooperation means, we can consider how it is that larger systems such as communities or even whole ecosystems maintain their stability. The question of how these systems maintain a fairly stable configuration is really only separated from more conventional consideration of altruism versus selfishness by scale.

An understanding of system stability must also inform our pursuit of sustainability. The overarching goal of the sustainability movement is to engineer a cultural system that is stable from the perspective of environment, economy, and social equity. But in order to achieve stability in any of these three areas (much less all three), we need robust scientific understanding of system stability. While I have not yet branched into this area, I am interested in considered how to model the stability (and therefore the sustainability) of human-engineered cultural systems.

You can see all of my blog posts related to system stability here.