Research 335: Ecosystem Tipping Points: Learning from the Past to Manage for the Future
Marine ecosystems are undergoing unprecedented change, with natural capital declining to the point that benefits accrued by humans are at risk. The tipping points project aimed to collate and integrate datasets describing the Celtic Sea ecosystem, to use these data to quantify how physical and biological ecosystem components have changed in recent decades and to establish relationships between ecosystem responses and external pressures.
Ecosystem change can occur abruptly in a non-linear fashion until a tipping point is reached and the ecosystem shifts to an alternative state. After a regime shift, the ecosystem may not return to its previous state, even when an external pressure is removed or reduced. This makes it difficult to predict ecosystem responses to human impacts and to identify appropriate indicators and targets for ecosystem-based management.
Environmental legal instruments such as the Marine Strategy Framework Directive (MSFD) and the OSPAR Convention prioritise holistic ecosystem-based management approaches. The dynamic nature of marine ecosystems makes the determination of ecosystem status, the identification of appropriate indicators and the setting of targets particularly challenging.
A primary objective of the project was to develop analytical tools for detecting step changes and to use these tools to determine if ecological tipping points have occurred in the Celtic Sea ecosystem. Significant progress was made in the early detection of ecosystem change points using the Bayesian online change-point detection algorithm.
The results from the project show that there has been considerable change in the physical environment in the Celtic Sea, primarily associated with ocean warming such as:
- Recorder (CPR) data showed a pronounced increase in the abundance of gelatinous zooplankton (jellyfish). Increasing jellyfish numbers are thought to indicate an ecosystem shift that may be triggered by climate change, overfishing, eutrophication, translocation and habitat modification.
- Simulations of herring larvae dispersal show a change in the delivery of herring larvae to nursery areas, owing to changes in wind patterns since the early 1960s, resulting in potential consequences for early life survival and recruitment to adult fisheries.
While a simultaneous regime shift across the ecosystem was not detected, there is strong evidence that change has occurred across multiple taxa and trophic levels in the Celtic Sea ecosystem over the last 50 years, which has important consequences for management.