This project developed and tested early warning indicators for ecosystem tipping points. The project provided the first proof-of-concept that tipping points can be anticipated in advance at scales relevant to ecosystem management and policy making. Results were communicated to researchers through journal articles and conference presentations, and the general public through news media. Two statistical packages for applying early warning indicators were created and made freely available.
In the field of ecology, regime shifts are massive changes in function and character that occur when an ecosystem passes a tipping point. Regime shifts sometimes have severe consequences for human well-being through losses of ecosystem services, including desertification in arid regions and marine fisheries collapses. These changes are difficult to predict and sometimes impossible to reverse. For these reasons, understanding how to anticipate and prevent regime shifts is one of the most important challenges faced by environmental scientists.
This project developed and tested early warning indicators for ecosystem regime shifts. This research was centered around a whole-lake experiment conducted with collaborators on two small lakes in the Upper Peninsula of Michigan. We manipulated the fish community of one lake to cause a trophic cascade—a type of regime shift—and made measurements throughout the food web to determine whether early warning indicators were detectable before the tipping point. An adjacent reference lake was monitored for comparison. Early warning indicators based on autocorrelation and variance responded strongly. Early warning signals were recorded up to a year and a half before the tipping point and were present throughout the food web including in time series of prey fish abundance, zooplankton biomass, and phytoplankton biomass. There were no early warning signals in the reference system. This was the first ecosystem-scale proof-of-concept that early warning indicators can be detected before tipping points. These results suggest that ecosystem managers may one day be able to use adaptive management to avert unwanted regime shifts. Outside of the lake experiments, this project included contributions to an international synthesis project that culminated with the development of freely available statistical software that can be used to apply the early warning indicators to time series or spatially explicit data.
The early warning indicators we developed and tested are generated by phenomenon that are general to complex systems and are not restricted to ecosystems. After our experiment, other research groups identified early warning indicators before regime shifts in a variety of complex systems, including in economic records before the subprime housing loan crisis, before the self-termination of epileptic seizures, and before shifts in social networking activity on Twitter. Hence, this project is exemplary of how fundamental ecological research can generate tools and concepts that provide diverse benefits to society.
I mentored two undergraduate students in research as part of this project. Our work together resulted in a peer-reviewed journal article co-authored by the students.
I contributed to the development of a website that features non-technical descriptions of theories and application of early warning indicators for ecosystem tipping points. Specifically, I wrote a case-study of application of early warning indicators during the whole-lake experiment. Related to this effort, I was part of an international synthesis group that developed two statistical packages for application of early warning indicators. These are freely available online and are run using the R statistical software.
Selected Media Reports
- An Early Warning Sign for Ecosystem Collapse? - Science
- Early Warning Signs - The Scientist
- Nature’s Warning Signal - The Atlantic
- 2016 Young Scientist Prize Winners - Science
- Gör viktiga experiment i sjöar - Västerbottens Kuriren
- A Tale of Two Lakes: One Gives Early Warning Signal for Ecosystem Collapse - National Science Foundation
- Scientists detect early warning signal for ecosystem collapse - University of Wisconsin
- Predicting environmental collapse - Cary Institute of Ecosystem Studies
- Science and SciLifeLab Prize for young scientists to environmental scientist David Seekell - Umeå University