Systems DynamicsSystems dynamics is a simulation method that allows us to understand complex behavior of a system of equations. SD allows us to explore complex behavior that results from feedbacks in a system. The system may be at the molecular level (molecular dynamics), the cellular level (metabolic pathways), the organismal level (homeostasis), the ecosystem level (food webs) or the global level (world models).


ECOMEECOME is a model of an evolving consumption (food) web, combining the equations for a food web with those of genetic evolution. The stability of an ecosystem can be explored in the context of inequality in the rate of evolution or adaptation. 

World4World 4 is a model for human population dynamics as humanity undergoes technologydriven hyperexponential explosion in the context of a finite planet.Projections of future global human population are traditionally made using birth/death trend extrapolations, but these methods ignore limits. Expressing humanity as a Kselected species whose numbers are limited by the global carrying capacity produces a different outlook. Population data for the second millennium up to the year 1960 was fit to a hyperexponential growth equation, where the rate constant for growth itself grows exponentially due an intrinsic growth of lifesaving technology. The underprediction of growth since 1960 is accounted for by a decrease in the global carrying capacity due to ecosystem degradation, in turn due to population overshoot. A system dynamics model that best fits recent population numbers reveals that the global biocapacity may already have been reduced to onehalf of its historical value and global carrying capacity may be at its 1965 level and falling. Simulations suggest that population may soon peak or may have already peaked. Numbers for the 2020 global census were not available for this study. 
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