One of the most important challenges facing ecosystem management
today is the development of effective management strategies to cope with the
increasing potential for complex and unexpected changes and still be able to
preserve critical marine ecosystem services.
Increasing amounts of observational data and powerful new mathematical approaches promise to substantially advance the development of strategies able to support sustainable management of marine ecosystems.
The challenge of how to move towards applied management strategies that include the possibility of unexpected changes, evolution, and adaptation provides the focus point for the latest ICES Journal of Marine Science themed set, “Science in a nonlinear, nonequilibrium world". Spearheaded by Gary Griffith, the Norwegian Polar Institute, a compilation of nine peer-reviewed paper are presented on thoughts, new methods, and applied research.
This new research will support ongoing discussions to inform marine management and policy on the need for a paradigm shift in management practices to include the “nonlinear nonequilibrium" perspective. Dispelling the mystery of nonlinear dynamics, nonlinearity in stock recruitment, ecological indicators to detect sudden changes and participatory management frameworks to consider nonlinearity and uncertainty are a few of the research topics covered. Griffith introduces the themed set, where he focuses on, "on three important areas—causality, prediction, and emergence—where a “non-linear” perspective can advance our understanding and better support sustainable management of ecosystems". A comprehensive overview, this is a good starting point for the reader.
Chaos theory to reconcile scientists and non-scientists
Over the last 30 years, the concepts of non-linearity and deterministic chaos have transformed ecological modelling. What has been achieved, in particular under the name of empirical dynamical modelling (EDM), responds to some of the issues that were originally highlighted, but not to all of them.
"Thirty years ago, it was hoped that non-linear thinking could help bring fishing professionals and scientists together around the concept of indeterminism" says Christian Mullon (MARBEC) who has co-authored, Modelling chance and necessity in natural systems, with Benjamin Planque (Institute of Marine Research). "While it is usual for fishers to expect some level of unpredictability in the resource, nonlinear approaches and deterministic chaos provide a way for fisheries scientists to represent such indeterminacy."
Mullon notes that nonlinear models are still rarely operational in fisheries today. "The model we are proposing is a step aside. Its main aim is to promote an open dialogue between fishers and scientists through the simple ideas of chance and necessity, that are familiar to all the actors (although they may have different views one these issues). The modelling approach can be used to reconstruct the possible dynamics of an ecological system taking explicitly into account available observations, their uncertainties and the assumptions that have been made. Ultimately, the resulting model is not a tool provided by scientists to fishers but rather a tool that is jointly elaborated by both parties. We observe together, and we learn together."
Non-linearity in stock–recruitment relationships
Camilla Sguotti (University
of Hamburg) welcomed the opportunity to contribute to this themed set with Non-linearity in stock–recruitment relationships of
Atlantic cod: insights from a multi-model approach, which she views shedding light on the presence
of non-linear dynamics in marine systems and offering a set of methods to model
and understand them. “We have
witnessed major changes in ecosystems worldwide and major irreversible reorganizations
of marine ecosystems with consequent socio-economic changes - this shows that
we live in a non-equilibrium/non-linear world that we need to be able to
understand and model in order to face the challenges of climate change while
being able to sustainably exploit our marine resources. Even though it is
now well-established that the natural world is mainly dominated by non-linear
and chaotic processes, the inclusion of these types of dynamics into management
is still difficult and seldom done. To avoid management failure and both ecological and socio-economic surprises, we need to develop/apply new methods which can
take these type of dynamics into account."
Sguotti’s paper looks at a
multi-model approach applied to the “typical” fishery problem of the
stock-recruitment relationship. “The stock-recruitment relationship is the
basis of every stock assessment and therefore management approach, but it is
still difficult to model as it is not clear what form this relationship has. Our paper compares three very different approaches to model and predict the
SR relationship of 20 stocks of Atlantic cod: the standard Ricker model, stochastic
cusp models which originate from catastrophe theory, and a data driven approach
from the Empirical Dynamic Modelling framework, called Simplex Projection. We have also integrated environmental drivers, which are known
to affect recruitment and productivity but are seldom included in stock
assessment. Our results show that different models need to be applied to
different dynamics if we want to have more powerful analyses and more trustable
predictions, important elements for a successful management.”
The latest issue of ICES Journal of Marine Science features two themed sets, Science in support of a nonlinear non-equilibrium world and Applications of machine learning and artificial intelligence in marine science. Both themed sets are free to access for all readers.
