IGB: Veranstaltungen: Abstract

Vasilis Dakos

Aquatic Ecology & Water Quality Management Wageningen University
http://www.aew.wur.nl/UK/Staff/VD/

Expecting the unexpected: From lake ecology to climate change

In the past years there has been increasing evidence that large scale abrupt changes in ecosystems, climate systems, oceanic circulation patterns and socio-economic systems may be explained by strong feedbacks which allow for nonlinear transitions between alternative states. Such sudden transitions (or “regime shifts”) are related to loss of resilience (sensu Hollling). In low resilience systems there is high probability that small disturbances can tip them into the basin of attraction of a contrasting state. Recent theoretical findings suggest that decreasing resilience has fundamental effects on the dynamical behavior of the system. Such effects appear to change in a consistent way as the system approaches the bifurcation point where the basin of attraction vanishes and the catastrophic transition takes place. When quantified, these effects can serve as early warning signals, enhancing our ability to assess the risk of upcoming shifts and to take precautionary actions to avoid them. In our work, we used simple mathematical models to investigate the applicability of different potential leading indicators in time and space. We follow the variance and autocorrelation of our state variables, while changing slowly a control parameter which brings the system close to the transition point. We show that our theoretical findings can have applications to a variety of systems that undergo critical transitions, like the climate system. We analysed eight ancient abrupt climate shifts and we found that all were preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Our work raises the question whether we will be able to apply the same indicators in more complex systems where multiple scales and multiple actors are at play.