1.2 - systems, tipping points, feedback loops, resilience, models

system

sets of inter-related parts working together to make a functioning whole

storages

stock of matter and energy within a system

• represented by boxes

flows

movement of matter and energy form one storage to another/ in and out of systems

• transfers → change in location of energy/matter

• transformations → change in the chemical nature, state or energy

*transfers and transformations require energy

• represented by arrows

boundary

limit that defines the extent of a system, distinguishing it from its environment.

input

matter or energy entering the system

to be processed or transformed.

output

matter or energy that exits the system after processing or transformation.

types of systems

• open system

• closed system

• isolated system

open system

exchanges energy and matter across the boundaries (majority of systems)

• organic

• natural forest ecosystem

• human body

closed systems

exchanges energy but not matter across boundaries (very rare)

*Earth can be considered an ALMOST closed system

• Biosphere 2 - closed system

isolated systems

exchange no energy or matter

• doesn’t occur naturally

• thermos flask

latent heat loss

as organisms respire they are loosing majority of their heat into their surroundings

emergent properties

are characteristics of a system that arise from the interactions of its components, which cannot be predicted by simply analyzing each part individually.

Earth, as a single integrated system, consists of

• biosphere

  • all parts where life exists

• lithosphere

  • crust, middle and center of Earth

• atmosphere

  • storage of gases

• cryosphere

  • frozen water parts of Earth

• hydrosphere

  • water mass on, under and over planet’s surface

• anthroposhpere

  • human-influenced environments, including urban areas and agricultural lands.

Gaia hypothesis - James Lovelock

• to explain how atmospheric composition and temperatures are interrelated through feedback mechanisms

• model of Earth as a single integrated system

• based on Earth’s consistency over the years

equilibrium types

• stable equilibrium

  • return to original equilibrium

• unstable equilibrium

  • return to new equilibrium after disturbance

feedback loops

stable equilibrium

• negative feedback loop

  • restricting or reversing a process to bring ecosystem back to original stable equilibrium

→ increased temperature → higher evaporation → clouds forming → cooling

unstable equilibrium

• positive feedback loop

  • amplifies changes in a system, leading ecosystem away from original equilibrium

→ melting of ice caps → gases released into atmosphere → higher temperatures → melting

real world examples of feedback loops

negative feedback loop

• predator-prey model

  • predator ↑ = prey ↓ = predator ↓ = prey↑

• Daisyworld model

positive feedback loop

• melting of ice caps → gases released into atmosphere → higher temperatures → melting

• birthrates ↑ = poverty ↑ = birthrates ↑

tipping points

minimum amount of change that will cause a significant shift in a system's state

• positive feedback loop

resilience

ability of a system to respond to disturbances and still maintain its core functions and structures.

• tendency to avoid tipping points and maintain stability

factors affecting resilience

• species diversity (more better)

• wider gene pool (bigger better)

• species that can shift location

• warmer climates (better as growth is faster)

• reproductive rates

• human activity (more is bad)

• sizes of storages

model

simplified representation of reality

• to understand how a system works

• to predict its response to change

advantages of models

• simplifying a complex reality

• identifying patterns

• predicting future changes

• can visualize both big and small systems

disadvantages of models

• loss of accuracy due to simplification and approximations

• may give very different results from actual data or other predictions

  • limited ability to capture dynamic interactions and unexpected behaviors

• simplifies sizes of inputs and outputs

• huge field for mistakes is assumptions are wrong

example of failed model

Imperial Collage, Ferguson’s Covid-19 model

• death toll was significantly over-exaggerated by 1000s of % points

• Sweden as natural experiment disproved the model

• model was used to justify global lockdowns leading to many negative consequences for societies

  • over-reliance of governments on inaccurate model