How Bali could teach the world to manage its limited resources
[Vienna, Oct 20, 2021] Water is a finite resource. As such, effective ways of jointly managing and optimizing water supplies are essential for our present and our future. But how do you establish a well-balanced system? In order to distinguish the relevant parameters, an international team of scientists, including Stefan Thurner of the Complexity Science Hub Vienna (CSH), applied a method of physics to a system in equilibrium: the centuries-old rice irrigation practices in Bali.
According to their work, which has just been published in Physical Review Letters, the current balance has been self-organizing over the past thousand years, possibly driven by the – contradictory – planting schedules of farmers.
Balance conflicting constraints
Over the centuries, Balinese rice farmers have had to face two constraints. On the one hand, the water to irrigate the rice fields is a limited resource. “Intuitively, one might think that an unsynchronized flood would lead to a more equitable distribution of water among farmers,” explains CSH President Thurner. Yet there is also a need to control rice pests such as insects which can easily move from field to field. Farmers have learned from experience that pest control requires synchronized flooding of neighboring rice fields.
These two constraints have opposite effects. “The larger the agricultural area that follows the same irrigation program, the more water stress appears from synchronized irrigation cycles,” the study reads.
To find patterns in synchronized and unsynchronized agricultural programs, scientists analyzed satellite images of several rice growing regions in Bali from 2002 to 2015. They ranked which of the four characteristic planting patterns – growth, harvest, flood or drainage – happened when and where. Now, they have developed a way to relate these patterns to the stress balance in Balinese agriculture.
A formula for a balance
“We present a formula that explains how a balance between water stress and pest stress is achieved and how the system ultimately achieves equilibrium,” says Thurner. “If the stresses were managed differently, the rice growing regions would be very different from what we see in reality. “
According to the complexity scientist, “it’s a very neat balance between different states and can switch to a tipping point or a phase transition point, as physicists would call it.”
How quickly the seemingly eternal balance can spiral out of control became evident in the 1970s. The so-called Green Revolution forced farmers to use pesticides and cultivate their paddy fields without their traditional timing system.
“At the beginning, the harvests increased”, explains Yérali Gandica of Cergy Paris University, first author of the article. “But within a few years, farmers have reported chaos in water supply schedules and an explosion of pests.” When too many rice fields in higher regions were flooded at the same time, farmers with lower terraces experienced water stress. The discord between neighbors has increased, the carefully cultivated Balinese culture of social harmony has been disrupted. It was only when the traditional method was restored that the equilibrium (largely) returned.
“This may seem like a very theoretical approach, but it could have a practical side in other ecological systems coupled man-environment: one can relate easily observable environmental models to the balance of the constraints – and thus to detect the weak points of their management “, concludes Thurner.
Yérali Gandica, J. Stephen Lansing, Ning Ning Chung, Stefan Thurner, Lock Yue Chew, Bali’s Ancient Rice Terraces: A Hamiltonian Approach, Physical Review Letters 127 (2021) 168301
+ + + + + + + + + + + + +
About the Complexity Science Hub Vienna (CSH):
The mission of CSH Vienna is to host, educate and inspire scientists of complex systems dedicated to making sense of Big Data to stimulate science and society. Scientists at the Hub are developing methods for the scientific, quantitative and predictive understanding of complex systems. Areas of focus include the resilience and efficiency of socio-economic and ecological systems, networked medicine, innovation dynamics and city science.
The Hub is a joint initiative of the Austrian Institute of Technology AIT, Central European University CEU, Danube University in Krems, Graz University of Technology, IIASA International Institute for applied systems analysis, IMBA, Vienna Medical University, TU Wien, VetMedUni Vienna, University of Vienna. of Economics and Business, and Austrian Economic Chambers (WKO).