1.2 Systems

• Sets of interacting or interdependent components

• Components organized to create functional whole

• Holistic way of visualizing complex interactions

• Applied to ecological or societal situations

• Has storages and flows (inputs and outputs of energy and matter)

• Storages: rectangular boxes

• Flows: arrows (direction indicates flow direction)

• Transfers: change in location of energy or matter

• Transformations: change in chemical nature, state, or energy

• Open: exchanges both energy and matter across boundary

• Closed: exchanges only energy across boundary

• Most systems are open (e.g., local ecosystem, Biosphere 2)

• Global geochemical cycles approximate closed systems

• Encompasses biosphere, hydrosphere, cryosphere, geosphere, atmosphere, anthroposphere

• Gaia hypothesis: Earth as single integrated system

• Small-scale: bromeliad in rainforest

• Large-scale: entire rainforest

• Global: atmospheric circulation, Gaia hypothesis

• Output inhibits/reverses same process to reduce change

• Stabilizing, counteract deviation

• Example: Daisyworld model (temperature regulation)

• Maintained by stabilizing negative feedback loops

• Steady-state equilibrium: inputs constantly balanced with outputs

• Tendency to return to equilibrium following disturbance

• Disturbance leads to amplification of disturbance

• Destabilizing, drives system away from equilibrium

• Examples: population decline → reduced reproduction → further decline

• Melting ice → reduced albedo → greater warming

• Positive feedback drives system towards tipping point

• Minimum change causing destabilization

• System shifts to new equilibrium/stable state

• Small alteration → large overall changes

• Result in regime shifts between alternative stable states

• Example: nutrient concentrations → eutrophication

• Simplified representation of reality

• Used to understand system function and predict responses

• Forms: graphs, diagrams, equations, simulations, words

• Simplification involves approximation

• Results in loss of accuracy

• Example: climate change predictions, population growth projections

• Appear from component interactions

• Components themselves don't have these properties

• Examples: predator-prey oscillations, trophic cascades

• Tendency to avoid tipping points and maintain stability

• Capacity to resist damage and recover from disturbance

• Diversity within systems

• Size of storages

• Affect speed of response to change (time lags)

• Example: prairie systems vs. monoculture crops

• Reducing storages and diversity

• Example: deforestation reduces storage size and diversity