1. Systems Theory Pedro Ribeiro de Andrade Münster, 2013

2. Geoinformatics enables crucial links between nature and society Nature: Physical equations Describe processes Society: Decisions on how to Use Earth´s resources

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

4. “A hypothesis or theory [model] is clear, decisive, and positive, but it is believed by no one but the man who created it. Experimental findings [observations], on the other hand, are messy, inexact things, which are believed by everyone except the man who did that work” Harlow Shapley (1885-1972), American astronomer

5. “[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 Models

6. What is a System?  Definition: A system is a group of different components that interact with each other  Example: The climate system includes the atmosphere, oceans, polar caps, clouds, vegetation…and lots of other things

7. How do we study systems? Identify the components Determine the nature of the interactions between components

10. Earth as a system

11. Systems Theory  Provides a unified classification for scientific knowledge.  Enunciated by biologist Ludwig Von Bertalanffy:  1920s: earliest developments  1937: Charles Morris Philosophy Seminar, University of Chicago  1950: “An Outline of General Systems Theory”, Journal for the Philosophy of Science  Scientists that introduced Systems Theory in their fields:  Parsons, sociologist (1951)  J.G Miller, psychiatrist & psychologist (1955)  Boulding, economist (1956)  Rapoport, mathematician (1956)  Ashby, bacteriologist (1958)

12. Short History of System Dynamics The System Dynamics approach was developed in the 1960s at M.I.T. by Jay Forrester. A system in Modelica

13. Conception of Reality  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 are opened or closed

14. A system  Can you identify parts? and  Do the parts affect each other? and  Do the parts together produce an effect that is different from the effect of each part on its own? and perhaps  Does the effect, the behavior over time, persist in a variety of circumstances? Source: (Meadows, 2008)

15. slide15 Systems Building Blocks  Stocks  Flows  Information Links  Decision Points  Converters  Auxiliary Variables

16. slide16 Stocks  “ Things ” that accumulate in a system  Physical or non-physical things  Value is a quantity or level  Persistent (remain even if all flows stop)  Conservation (stock units enter from environment and return to environment)

17. slide17 Flows  Movement of “ things ” in and out of stocks  Not persistent (can be stopped and started)  Value is a rate of change (will always have a time dimension)  Flow unit = stock unit / time  The unit of measurement for a flow will always be the unit of measurement of a stock divided by an element of time

18. slide18 Stock and Flow Diagram  Stocks in boxes  Flows as straight double arrows  Information Links as thin curved arrows  Decision Points as closed in X

19. Control Material Flaw to Stock Add New information Send information from the Stock Control Material Flaw from Stock Stock System Dynamics Modelling

20. Shrimp farming

21. Simple model for shrimp farm

22. Results? Figure 7

23. Positive Coupling Atmospheric CO 2 Greenhouse effect An increase in atmospheric CO 2 causes a corresponding increase in the greenhouse effect, and thus in Earth’s surface temperature Conversely, a decrease in atmospheric CO 2 causes a decrease in the greenhouse effect

24. Negative Coupling Earth’s albedo (reflectivity) Earth’s surface temperature An increase in Earth’s albedo causes a corresponding decrease in the Earth’s surface temperature by reflecting more sunlight back to space Or, a decrease in albedo causes an increase in surface temperature

25. The interesting thing to do is to put couplings together in feedback loops…

26. person A’s body temperature person A’s blanket temperature Negative Feedback Loops: Electric Blankets person B’s blanket temperature person B’s body temperature

27. person A’s body temperature person A’s blanket temperature A Positive Feedback Loop: Mixed-up Electric Blankets person B’s blanket temperature person B’s body temperature

28. A Positive Feedback Loop: Mixed-up Electric Blankets Any perturbation will cause both people to adjust their blanket controls, but with undesired consequences. Ultimately, one person will freeze (become infinitely cold) and the other person to swelter (become infinitely hot).

29. Equilibrium State: Conditions under which the system will remain indefinitely --If left unperturbed

30. An Unstable Equilibrium State

31. Perturbation

32. When pushed by a perturbation, an unstable equilibrium state shifts to a new, stable state.

33. A Stable Equilibrium State

34. Perturbation

35. When pushed by a perturbation, a stable equilibrium state, returns to (or near) the original state.

36. Tools for system dynamics  Dinamo  Vensim  Simile  STELLA

37. 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

38. Cell Not yet (description extracted from “TerraME types and functions”)

39. Event Not yet

40. Temporal model Source: (Carneiro et al., 2013) 1:32:10ag1:execute( ) 1:38:07ag2:execute( ) 1:42:00cs:save()... (4) ACTION return value true (1) Get first EVENT 1:32:00cs:load( ) (2) Update current time (3) Execute the ACTION false (5) Schedule EVENT again

41. Observer Not yet

42. 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

43. Water in the tub 2  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

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