Patagonia case study: STM Model

By: Graciela Rusch (NINA), Veronica Rusch (INTA), Santiago Varela (INTA), and Anders L. Madsen (HUGIN)
14 September 2016

Introduction

State-and-Transition models (STMs) when applied to managed systems are graphical, heuristic models that make use of ecological knowledge from diverse sources to describe quantitatively ecosystem responses to management. STMs are models of ecosystem condition that integrate use and management as ecological factors driving ecological change. We built an STM of native Nothofagus antarctica (Ñire) forest under silvopastoral use (cattle production and fuel wood extraction) in northern Patagonia, Argentina. There are indications that some levels of use are likely to be unsustainable, i.e., they can drive the silvopastoral system to a condition with low tree cover where critical ecosystem services are lost with time. Logging can exceed the capacity of the system to produce wood and cattle grazing damages tree seedlings and saplings, hindering the recruitment of new trees. Ñire trees are thought to live ca 150 years.

According to the National Law for Conservation of Native Forest, the tree cover and the ecosystem services generated by forest should be maintained in time. We have modelled the capacity to generate five ecosystem services by this system, i.e., fuel-wood production, habitat quality for native fauna, grass production, protection of soil and water and recreation quality. We model how this capacity may change with different levels of use.

By implementing the STM as a Bayesian Belief Network (BBN), we have incorporated levels of uncertainty linked our knowledge about the system.

Interactive Front-end

Below are some HUGIN widgets for interacting with the model.

References

Rusch, V. E., A. Goijman, P. Peri, D. Lopez, L. Claps, M. Sarasola, A. Cardozo, and G. M. Rusch. 2015. State-and-Transition models: A tool to analyse decision-making and ES delivery. Fourth International Congress of Ecosystem Services in the Neotropics, Mar del Plata, Argentina.

Rusch, V. E., D. Lopez, L. Cavallero, G. M. Rusch, P. Peri, A. Cardozo, N. Hansen, A. von Muller, L. A. Garibaldi, and M. Sarasola. 2015. An ecological framework to establish management boundaries. The case of ñire forests of northern Patagonia, Argentina. VIII Congreso Internacional de Sistemas Agroforestales, Puerto Iguazu, Misiones, Argentina.

Useful references for those interested in BBN include:

Kjærulff, U. B. and Madsen, A. L. (2013) Bayesian Networks and Influence Diagrams: A Guide to Construction and Analysis. Springer, Second Edition.

Contact information

For further details on the paper: Graciela Rusch

For further details on the use of Bayesian networks and web deployment of models contact: Anders L Madsen (alm(at)hugin(dot)com)

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