System Dynamics Pedro Ribeiro de Andrade So Jos

System Dynamics Pedro Ribeiro de Andrade São José dos Campos, 2016

How to model Natural-Society systems? Connect expertise from different fields Make the different conceptions explicit If (. . . ? ) then. . . Desforestation?

Models “[The] advantage of a mathematical statement is that it is so definite that it might be definitely wrong…. . Some verbal statements have not this merit; they are so vague that they could hardly be wrong, and are correspondingly useless. ” Lewis Fry Richardson (1881 -1953) – first to apply mathematical methods to numerical weather prediction

A system is a group of different components that interact with each other ▪ Can you identify parts? ▪ Do the parts affect each other? How?

Earth as a system

System Dynamics ▪ Any measurable part of reality can be modeled ▪ Systems are represented as stocks and flows Stocks represent energy, matter, or information ▪ Flows connect and transport stocks ▪

Systems Theory: stocks and flows Stocks: measurable elements Flows: changes in stocks over time source: Meadows, 2008

Water in the tub ▪ ▪ ▪ Initial stock: water in tub = 40 gallons water in tub(t) = water in tub(t – dt) – outflow x dt t = minutes dt = 1 minute Runtime = 8 minutes Outflow = 5 gal/min

Water in the tub ▪ ▪ ▪ ▪ Initial stock: water in tub = 40 gallons water in tub(t) = water in tub(t – dt) – outflow x dt t = minutes dt = 1 minute Runtime = 8 minutes Outflow = 5 gal/min Inflow = 40 gal every 10 min

Conclusions ▪ Two ways to increase stocks ▪ Stocks act as delays or buffers ▪ Stocks allow inflows and outflows to be decoupled