Author Archives: vdakos

Trends in variability and autocorrelation in observed global temperature records

Figure 1Back in 2012, we started exploring how patterns in the magnitude and persistence of fluctuations in instrumental records of temperature and their major global sea and land indices might have changed during the last century. Our objective was to identify regions where climate variability and autocorrelation might have markedly increased potentially due to anthropogenic forcing. We just published the results of this work in a paper titled Observed trends in the magnitude and persistence of monthly temperature variability. The main findings are summarised here.

 

Evaluating early-warning indicators of critical transitions in natural aquatic ecosystems

pnas-2016-gsell-1608242113We 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.

PAGES Issue on Climate Tipping Points

PAGESIn 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.

Monitoring economic variables to infer ecosystem resilience

profit fluctuationsStrongly 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.

Hysteresis and Heteroskedasticity (early view papers)

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).

Principles for Building Resilience: Sustaining Ecosystem Services in Social-Ecological Systems

We tried to bring together evidence of how the widely discussed notion of resilience can be beneficial in sustaining the equally discoursed ecosystem services in the context of social-ecological systems. That is building resilience looking at both parts of the equation: the environmental setting and the human component. A multidisciplinary project around the theme of resilience that started from a get-together 7 years ago, turned into a paper and made it into a book.

7-principles-cover_web

Book Summary: As both the societies and the world in which we live face increasingly rapid and turbulent changes, the concept of resilience has become an active and important research area. Reflecting the very latest research, this book provides a critical review of the ways in which resilience of social-ecological systems, and the ecosystem services they provide, can be enhanced. With contributions from leaders in the field, the chapters are structured around seven key principles for building resilience: maintain diversity and redundancy; manage connectivity; manage slow variables and feedbacks; foster complex adaptive systems thinking; encourage learning; broaden participation; and promote polycentric governance. The authors assess the evidence in support of these principles, discussing their practical application and outlining further research needs. Intended for researchers, practitioners and graduate students, this is an ideal resource for anyone working in resilience science and for those in the broader fields of sustainability science, environmental management and governance.

 

Detecting tipping points in ecological networks

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.

The use and misuse of resilience indicators as early warnings for regime shifts

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.

ASLO organized session: Regime shifts in lakes, rivers, and oceans

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.