Source link : https://jpc.news/2024/12/08/ecology/article13396/
Exploring Multi-Scale Complex Systems: A New Theoretical Framework
Complex systems are pervasive in various domains, including immunology, ecology, economics, and thermodynamics. However, effectively modeling these systems poses significant challenges. Traditional methodologies generally adopt either a bottom-up or top-down perspective. Yet in altered environments—such as ecosystems recovering from wildfires or societies grappling with pandemics—these one-dimensional models fail to accurately represent the intricate interactions between small-scale behaviors and overarching system characteristics. To tackle this issue, SFI External Professor John Harte at UC Berkeley and his collaborators have developed an innovative hybrid approach that integrates both bottom-up behaviors and top-down influences into a unified theoretical framework.
Integration of Perspectives in Understanding Ecosystems
In their recent publication in PNAS dated December 6, researchers led by Harte present their methodology alongside four simplified case studies illustrating its potential applications.
Harte states, “Throughout the last 14 years, we’ve produced numerous studies demonstrating that the top-down model is instrumental for uncovering ecological patterns.” He adds that this method validly predicts relationships within ecosystems such as the species-area relationship—which describes how biodiversity expands with larger habitats—and variations concerning species abundance and body size distribution. However, he notes an important caveat: “Six years ago we realized that during times of severe disturbance within an ecosystem—when overarching properties are unstable—the top-down model falls short.”
This realization propelled Harte’s team to construct a theoretical framework capable of capturing both the dynamic properties of complex systems undergoing change and the probability distributions relevant to their individual components.
The Role of Disturbances in System Dynamics
Disturbances—with their resulting two-way feedback loops—are evident across many types of complex systems. For instance, during a pandemic scenario where traditional Susceptible-Infected-Recovered (SIR) models gauge infection probabilities based on proximity to infected individuals—it becomes apparent these models overlook critical interactions between micro-level behavior changes and macro-level trends. As reported cases escalate at a broader level, shifts in individual behavior may subsequently lead to declines in transmission rates.
In economic contexts as well, personal decisions regarding employment opportunities or consumer purchases are significantly influenced by macroeconomic indicators like GDP growth rates or inflation levels—all while consumer expenditure remains a key driver affecting overall economic health.
In 2021, Harte’s team introduced their hybrid theory through their article “DynaMETE: a hybrid MaxEnt-plus-mechanism theory of dynamic macroecology,” published in Ecology Letters. Their initial applications tested data from an ecologically disrupted forest site in Panama wherein they demonstrated that this new model could elucidate transformations within species distribution patterns. The authors now propose broadening the applicability of their findings across diverse scenarios.
Advancements Beyond Previous Models
“This conceptual model enables us to derive calculations previously thought unattainable,” notes Harte. “Within these bi-level frameworks characterized by dual influences—top-down pressures aligning with bottom-up dynamics—it becomes vital to assess how both individual components and the overall system will evolve over time when disturbances occur.”
To further validate this theory’s robustness across various contexts including more controlled environments like combustion tanks—a fundamental thermodynamic setup—they acknowledge additional empirical testing is necessary. “Our primary breakthrough was appreciating just how pivotal our question is,” states Harte regarding ongoing research endeavors aimed at affirming or refining this newly proposed theoretical structure amid differing conditions.
As highlighted by current challenges presented within non-equilibrium thermodynamics exemplified by proposed experiments using combustion tanks—the accurate forecasting of molecular kinetic energy distributions has remained elusive until now according to Harte’s observations.
The hybrid model presents promising avenues not just for laboratory exploration but also provides valuable insights into pressing challenges faced globally—from climate fluctuations to health crises—to economic uncertainties affecting many livelihoods today.
For further exploration on this subject matter refer to “Dynamical theory of complex systems with two-way micro–macro causation” available through PNAS (December 6th edition). DOI: 10.1073/pnas.2408676121
The post Revolutionizing Your Understanding: How Hybrid Theory Transforms the Modeling of Complex Disturbed Systems first appeared on JPC News.
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Author : Jean-Pierre CHALLOT
Publish date : 2024-12-08 21:20:22
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