We just published a study on signatures of instability in empirical time series from five freshwater ecosystems with documented sudden, persistent transitions hypothesized to represent critical transitions. We detected strong variation in early warning indicators, and a low agreement between the four indicators we tested. We conclude that the applicability of these tools was strongly limited by the requirement for ecosystem-specific knowledge of transition-generating mechanisms and their drivers to choose relevant state variables for analysis, especially in monitored systems that are not explicitly designed for estimating this type of indicators.
In the just published PAGES issue of Past Global Changes there is a science highlight on Tipping points or “Lessons from the Past for the Future” as the editorial suggests. In ten short 2-page contributions the most up-to-date ideas about past climatic transitions are highlighted together with examples from ecological and socio-ecological abrupt shifts. We have contributed in this issue a short piece on how the shift of the Sahara has been shaping our thinking about abrupt change.
Strongly coupled socio-ecological systems propagate their effects and disturbances one to the other. This has been demonstrated in most studies of human management of common resources. In recent work, we show that indicators of decreasing resilience can also propagate from one system to the other. For example, an increasingly harvested fish stock might reflect its eroding resilience in the profits of its harvesters. This generally implies that monitoring socio-economic variables that are linked to natural resources can indicate the resilience of the socio-ecological coupled system as a whole.
After 3 beautiful years in Spain, I am getting quite excited starting up a new postdoc position in Switzerland at ETH in Zurich. I will be part of a multidisciplinary program bringing together geneticists, ecologists, and biologists studying empirically and theoretically adaptation to a changing environment.
Only a handful of studies demonstrate the existence of hysteresis in bistable systems. In a follow-up from our earlier work, we study the recovery trajectory of a light-stressed plankton population in a chemostat experiment (early view in Oikos). We find that reverse trajectories can be explained by hysteresis, time-delays and adaptive process, all of which pose interesting questions for the behavior of bistable systems under changing conditions.
Recently, we summarized a set of measures that can be used as spatial indicators for detecting loss of resilience. We now add another measure that can be used as early warning of critical transitions in spatially explicit systems: spatial heteroskedasticity. In short, this indicator is the analog of conditional heteroskedasticity in timeseries (the non constant variance along a timeseries). We now expand its use from indicator of critical transitions in timeseries to spatial data (early view in Ecology & Evolution).
In this just published paper we develop a framework of detecting tipping points in the context of mutualistic networks. Under a scenario of global environmental change that might affect species interactions we show how indicators of resilience could provide early warning in complex communities such as those represented by the network of interactions between plants and their animal mutualists. This work is a first step towards quantifying the risk of network collapse and the possibility to monitor community resilience based on best-indicator species.
Regime shifts have been a long sought theme of research in marine ecosystems. Controversies, new methods and alternative hypotheses on how to study and understand such marine regime shifts are summarized in the special issue of the Philosophical Transactions of the Royal Society on Marine regime shifts around the globe: theory, drivers and impacts that just appeared online. Thus, we couldn’t think of a better place to publish a review-research paper on the use and misuse of resilience indicators as early warnings for regime shifts in marine but not only systems.
Together with David Seekel and Jessica Gephart, we are organizing a session on regime shifts in the upcoming American Society for Limnology & Oceanography conference in Granada, Spain in February 2015. The abstract submission is open with a deadline on the 10th of October 2014.
A new experience attending a conference of another community for the first time. European Conference on Complex Systems in Lucca Italy. A mix of physicists, mathematicians and engineers. Probably few ecologists and biologists, although one of the complex systems track on the conference is about living systems. I hope I can get inspired and make some new connections with my talk.
Just a week before the resilience conference 2014 in Montpellier a short brochure of our forthcoming book on “Principles for Building Resilience: Sustaining Ecosystem Services in Social-Ecological Systems” (Cambridge University Press, 2014) has become available by the Stockholm Resilience Center. The brochure summarizes the expanded treatment of resilience principles as we have discussed in an earlier paper “Towards principles for enhancing the resilience of ecosystem services“.