Systems Approach (AQA A Level Geography)

What is system thinking?

• A way to simplify and contextualise a complex world
• One of the key A-level concepts along with equilibrium, thresholds and feedback loops that are needed to be utilised
• Helps to understand how physical landscapes work and interact with each other, but also what the impact of human activity has on them

What is a system?

• Systems have structure and are considered:

a group of interacting parts connected by flows or transfers of energy, material, or matter

• All systems have boundaries; the global hydrological system's boundary is the upper atmosphere
• There are open and closed systems:
  • Open systems have external inputs and outputs of energy and matter exchange at its boundaries
  • Closed systems only have energy as their input and output, matter is contained within the system boundary
  • Energy is from the sun, which is irradiated back from Earth to space
• Within global systems, there are usually numbers of smaller subsystems, e.g. drainage basin of a river
• Cascading systems are where energy and material are transferred from one subsystem to another
• The output of one subsystem then becomes the input for another subsystem: alluvium from a river cascades into the coastal system

Diagram of closed vs open systems

Earth's global systems

• The Earth is one global system in its own right and is a closed system as the only input is energy from the sun (apart from the odd meteorite!)
• Within this global system are four major systems, which are all interconnected and have their own subsystems
  • Atmospheric system: interaction of the gases around the planet
  • Hydrosphere system: interaction of water on our planet
  • Biosphere system: interaction of biological life with our planet
  • Lithosphere system: interaction of the solid, semi-solid, and liquid land of the planet's crust

Components of a system

• Systems have inputs, throughputs and outputs
• Within the system boundary are stores, flows or transfers and processes (e.g. erosion, transport, etc.

Systems Terminology

System Term	Definition	Example
Input	Matter or energy moving into a system from the outside	Precipitation
Output	Matter or energy moving from the system to outside the system or to another system	Surface runoff
Energy	Power or driving force	Insolation
Stores/components	Individual parts/elements of the system	Puddles, soil, trees, etc.
Flows/transfers	The movement of parts within the system	Evaporation, throughflow, fallout etc.
Processes	The stores/components and inputs are worked upon and changed	Photosynthesis, erosion etc.

 

•  A natural system is complicated and needs many inputs, processes and outputs, which don't happen at once but are needed to maintain equilibrium/balance

Equilibrium 

• This is a state of balance within systems where inputs and outputs are equal and processes operate to maintain the balance
• Any disturbance will affect the balance and throw that system into change
• For example, undercutting the bottom of a slope to build a road
  • This destabilises the slope, making it liable to mass movement
  • The system has been changed into an active slope development system 
  • To return to balance, a system of feedback loops is employed

Feedback loops

• Feedback mechanisms are active in systems to maintain or restore equilibrium
• These can be positive or negative
  • Positive feedback amplifies the change 
    • It is where one change leads to another 
    • The change becomes bigger and moves the system further away from balance
    • For example, global warming increases permafrost thawing, which releases methane (a greenhouse gas) into the atmosphere, which causes more warming, which in turn causes more thawing, etc.
  • Negative feedback 'checks' or dampens change
    • It is self-regulating to promote stability and maintain equilibrium
    • E.g. a rock suffers freeze-thaw weathering and the debris eventually covers the rock
    • This debris acts as protection and dampens the effects of further weathering of that rock

Dynamic equilibrium

• A system in a steady, total state of balance is difficult to find, as nature is dynamic
• Constant short-term adjustments, usually through negative feedback, are made to maintain the balance and this is referred to as 'dynamic equilibrium' 
• As nature does not stand still, over time, the whole system may change to another system
• E.g. a storm on a coast increases sediment loss on a beach due to high energy waves and deposits it off-shore
  • As the storm abates, low-energy waves bring sediment back to shore and begin to rebuild the beach profile
  • Eventually, a new dynamic equilibrium is reached