The complexity of the world in one model

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BY Inge Janse

November 2018

If you want to do justice to the reality of a situation, you have to pay attention to its complexity. George van Voorn took this idea as the basis for a model for describing the resilience of a system. In the context of overfishing in the Philippines, for example.

Many Filipinos opt for a career in tuna fishing for the money they can earn. This sometimes leads to overfishing. The government of the Philippines is trying to get fishers to stop this through financial incentives. Only it is not working. Cultural norms and values appear to weigh heavily. “My grandpa started this fishery, it would be shameful for my family if the business was closed down.”

Yellowfin tuna is delivered to the fish market in General Santos in the Philippines.


So the reality is clearly more complex than the model used by policymakers. This is the inspiration for WUR mathematician George van Voorn and his colleagues to figure out a model that does work. The result offers a socio-ecological sketch of the resilience of tuna fisheries in the Philippines. “Human behaviour turns out to be the main component that can be adapted. If you look at the resilience of a system without the people, you are not looking from the right perspective.”

Playing with variables

So instead of modelling fisheries as a biological system, the researchers came up with an agent-based model. The behaviour of individuals is coded according to rules: how do they respond to each other and to the system? “This enables us to simulate what really happens. Then you can play with the variables, such as economic stimuli and social norms, and look at the outcomes.”

‘Financial incentives are useless for getting fishers to stop but social rules work’

What emerged was not only that financial incentives are useless for getting fishers to stop, but also that social rules can be used to this end. “The fishers use buoys to attract fish. The social norm is that fishers do not go near each other’s buoys. That makes it possible to tackle the pressure on fish stocks by spreading out the buoys.”

Philippine fishers use buoys to lure yellowfin tuna. PHOTO Alamy

In order to translate ‘the system’ into an agent-based model, WUR experts from all sorts of fields came together. Mathematics, biology, policy, economics, and programming: they were all represented, with the aim of doing justice to the complexity of the reality. “That made for academically tough but not unfriendly debates. We got along fine because in that model we had a shared goal.”

WUR experts from a range of fields are collaborating on translating ‘the system’ into an agent-based model.

What is new about Van Voorn’s work is the complexity of the model. Research often focuses on just one part of the system, such as economics, ecology or sociology. Van Voorn and his colleagues take a transdisciplinary approach so as to arrive at a socio-economic system that transcends subject boundaries. Using existing data they created a model that does justice to the reality, including all the underlying issues related to different disciplines. “You’ve got to do that because everything is interrelated. Experts have got to step out of their silos, get together, and come up with a single overarching concept.”

Clear alternative

Because this kind of interdisciplinary research is in its infancy and is not very easy to translate into interventions, Van Voorn’s model has not yet led to a change of thinking among policymakers in the Philippines. “My co-authors are talking to stakeholders there, to see how the model should be extended. But at least our model provides a clear alternative to the old model the policy is based on.”

‘Mathematics, biology, policy, economics and programming: they were all represented. That made for academically tough but not unfriendly debates’

The real difference his work makes is that it sets a modest ball rolling through the world of research on resilience. “We have just published an article in which we call on colleagues to look at systems in socio-ecological terms. That is the beginnings of awareness. In 20 years’ time we shall know whether we were successful.”

There is certainly growing momentum, in any case, because at the beginning of 2019 a large project on modelling socio-ecological systems will start at the four technical universities in the Netherlands, involving 16 researchers, from sociologists and biologists to mathematicians and urban planners. “We hope this will make this concept more usable for policymakers, as a kind of thermometer for the resilience of a system.”


George van Voorn PhD


Researcher, assistant professor, biologist and mathematician at Wageningen University & Research

Resilience research

Using mathematical models for research on the resilience of semi-natural systems such as agriculture, fisheries and managed forests


George van Voorn works on this research with a team of WUR scientists in the fields of socio-economics and sustainable agriculture and horticulture

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