"Phase Transition" in Complex Ecosystem

A few months ago, I was trying to explain the limitations of modeling because of lack of data on something rudimentary as "Phase Transition" (simplest example - ice becomes gas without becoming water). 

We as a civilization never got educated on complex systems and hence, we are facing so many problems masqueraded as "political" polarization. I hope future generations will look back and laugh at the ridiculousness of our current state. 

Insights from a great interdisciplinary research:

Your gut is home to microbial madness. Hundreds of trillions of bacteria belonging to countless species interact with one another in complex ways that can both keep you healthy and cause disease. Teasing out these interactions would seem an impossible task.

Now, microbiologists have found help from an unlikely source: physics. A new experiment suggests a powerful concept known as a phase transition can predict how complex ecosystems—like those composed of the bacteria in your belly—behave. The finding could help us keep our guts healthy and even protect other complex ecosystems such as rainforests and coral reefs.

“It’s a beautiful piece of work,” says Fernanda Pinheiro, a physicist who studies bacterial ecology and physiology at the Human Technopole, who was not involved with the work.

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To get at the problem, Massachusetts Institute of Technology (MIT) physicist Jeff Gore and his colleagues created bespoke ecosystems in the lab. They scooped up 24 bacterial species from the soil of a Boston-area nature preserve and swiped another 24 from nematode guts. They grew the microbes together in plastic wells and increased and decreased the concentration of nutrients to manipulate how strongly the different species interacted with each other. The more nutrients, the more the different species competed.

The experimental ecosystems went through three distinct phases as the number of species in the mix or the intensity of interactions between species increased. At first, every species’ population remained stable. Then, when the number of species or the interactions between species crossed a certain threshold, the system abruptly entered a new phase in which some species started to die out. As the experimenters kept adding species and ratcheting up nutrient levels, the system crossed into a third phase: The remaining species’ populations began to fluctuate wildly, indicating the ecosystem as a whole had lost stability.

The upshot: Just two variables—the number of species and the average interaction strength—determined whether a mishmash of different microbes would be stable or chaotic, says study author Jiliang Hu, a mechanical engineering graduate student at MIT.

The paper, published today in Science, is the first to report replicable phase transitions based on species interactions and diversity in communities with more than a tiny handful of species, Kuehn says.