Stability and Fluctuations in Complex Ecological Systems


8 - 12 August 2022

Venue: Lorentz Center@Oort

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One of the key questions in ecology is how assemblages of species-rich communities form
stable networks combining persistence with population fluctuations. For many decades, re-
searchers have studied whether, and how, biological diversity might influence community sta-
bility. And yet, we still do not have a sufficient understanding of the strength and the nature
of all ecological interactions in communities and how that affects network stability. In par-
ticular, there is recent interest in understanding how population fluctuations due to temporal
and spatial variability affect co-occurrence in ecological networks. Importantly, these studies
are useful for assessing the complexity of ecosystems, and for predicting ecosystem resilience
to perturbations or environmental change and disturbance.

Population fluctuations, both deterministic and stochastic, play a key role in ecosystems.
Sources of stochasticity (random noise) can be internal, such as organisms producing a vari-
able number of o spring, or external, such as environmental variability. Even small amounts
of noise can cause a large fluctuation in a population level, which can then lead to popu-
lation extinction. On the other hand, environmental noise can be beneficial, for example
enabling competitive species to coexist. Deterministic fluctuations, such as seasonality, also
affect extinction and coexistence, as well as invasion and colonisation (or recolonisation). It
is therefore important to understand the inextricable relationship between population fluctu-
ations and community stability, and to develop new combinations of theoretical and empirical
approaches to quantitatively study fluctuations and stability.

These different lines of research have to a large extent been developed in a relatively
independent manner with little interaction between ecologists, mathematicians, and physicists.
One of the aims of the workshop is therefore to bring together scientists looking at complex
ecosystems from different angles, in order to arrive at an improved understanding of stability,
vulnerability, and other ecosystem properties. A dialogue between these different groups is
critical to determining the role of deterministic and stochastic fluctuations and to determine
which models best capture the ecology while remaining tractable to mathematical analysis.
The necessity of this workshop has gained momentum from the ongoing worldwide biodi-
versity crisis that asks for fundamental understanding of how complex biological communities
will be a ected by demographic, environmental, and seasonal change and disturbance. This
interdisciplinary approach will enable improved understanding of the dynamical interactions
of complex ecosystems and how these dynamics may be used to predict stability, including
shifts in stability and potential consequences in terms of ecosystem collapse.

To facilitate interdisciplinary interactions, the workshop will focus on the following two
Theme 1: Stability versus complexity in ecological systems. In addition to considering
deterministic approaches, we will also discuss the role of stochastic effects and how early-warning signals can be used to better understand these systems. Both theoretical and
empirical studies will be emphasised.

Theme 2: Deterministic and stochastic fluctuations in ecological systems. We will
discuss the effect of seasonality and random noise on the extinction and persistence of
species, as well as on invasion and (re)colonisation. We will also discuss spatial dynamics,
with an eye toward how fluctuations affect the dynamics. The role of early-warning
signals in spatial systems and systems undergoing fluctuations will be discussed.


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