Authors: Deirdre Brophy, Cóllín Minto, Olga Lyashevska, Róisín Nash, Ian O’Connor, Tom Doyle, Damien Haberlin and Kieran Lyons
Summary: Marine ecosystems are undergoing unprecedented change, with natural capital declining to the point that benefits accrued by humans are at risk. This project aimed to collate and integrate datasets describing the Celtic Sea ecosystem, and to use this data to quantify how physical and biological ecosystem components have changed in recent decades and to establish relationships between ecosystem responses and external pressures.
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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. 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.
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. The analysis of long-term environmental and biological datasets can support the implementation of the MSFD and other ecosystem management approaches by providing a historical context for changes in indicators, allowing natural short-term variability to be separated from long-term trends, regime shifts to be detected and links between ecosystem components to be identified. The ultimate goal for researchers, managers and policymakers is to develop early warning indicators that signal an approaching threshold before it is reached, allowing management to respond to avert a regime shift.
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. 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.