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Introduction
Introduction
This session we will explore dynamics of ecosystem change using the Ecosim module of EwE. Ecosim extends the static, mass-balanced models of Ecopath into time-dynamic simulations, enabling you to explore how ecosystems respond to food web effects, environmental changes, fishing pressure, and other human and natural impacts. You will be introduced to the foundational concepts of time dynamic modelling through the foraging arena theory, which incorporates behavioural and spatial aspects into predator-prey interactions. We will use a simple food chaing model to simulate ecosystem dynamics and impact of fishing at different trophic levels, gaining an introduction into how these tools can support effective ecosystem-based management.
Key topics and concepts
Time-dynamic simulations: How ecosystems change over time in response to internal and external drivers.
Foraging Arena Theory: The behaviour-driven partitioning of prey populations into vulnerable and invulnerable components, improving model realism and behaviour.
Time-series fitting: This involves calibrating models with observed data to improve accuracy and reliability in order to use models to replicate ecosystem history. At this short course, we will not cover this aspect in any detail.
Vulnerability multipliers: the key Ecosim parameter, which is a function of where populations are relative to their carrying capacity .
Learning outcomes
Learning outcomes
This session will provide an introduction to and experience with,
Applying theoretical concepts in a practical setting by constructing a simple food chain model, and using it to evaluate impact of fishing pressure at different trophic levels, and evaluate ecosystem effects such as cascading.
Dynamic modelling and how it is implemented in EwE
The principles of time-dynamic ecosystem modeling and differentiation between static Ecopath models and dynamic Ecosim simulations in terms of their capabilities and applications.
Applying foraging arena theory concepts to understand how prey populations are partitioned into vulnerable and invulnerable components and how this affects predator-prey dynamics in ecosystem models.
Analyzing the role of vulnerability multipliers as key Ecosim parameters and evaluation of how they influence trophic interactions based on population status relative to carrying capacity.
Simulating ecosystem responses to fishing pressure at different trophic levels using simple food chain models to demonstrate cascading effects through the food web.
Assessing the potential of dynamic ecosystem models for supporting ecosystem-based management decisions by interpreting model outputs and understanding their applications in predicting ecosystem responses to environmental and anthropogenic changes.
Resources and preparation
Resources and preparation
To prepare for the session, please read through the following chapters in the EwE textbook:
On modelling and making prediction. A story about ecosystem modelling and how we got to be where we are with EwE. Foraging Arena Theory and how it came to be explains why we now can make ecosystem models that replicate the ecosystem history and make plausible predictions.
Foraging arena theory. A detailed description of foraging arena theory that's a bit heavy on the math and quite comprehensive. Read it to get an overview, OK not to go into the details.
A primer on dynamic modelling. A very brief introduction to how dynamic models integrate over time
Introduction to Ecosim. A very brief introduction.
Environmental impact. The inner workings of how Ecosim and Ecospace incorporates environmental impacts. Also used for evaluating impact of climate change.
Mediation. Explains briefly how the dynamic components of EwE (Ecosim and Ecospace) incorporates indirect (non-trophic) impacts.
Presentations
Presentations
Please look through lectures before class.
02: Ecosim introduction.
03: Tales from the foraging arena (Carl Walters)
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