Systems Approach (AQA A Level Geography)
Revision Note
Written by: Jacque Cartwright
Reviewed by: Bridgette Barrett
A Systems Approach to Geography
What is system thinking?
It is a way to simplify and contextualise a complex world, its relationships and interactions within itself and between other systems
One of the key A-level concepts along with equilibrium, thresholds and feedback loops, that are needed to be used
It 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, closed and isolated 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
Isolated systems do not share matter or energy with their surroundings
Isolated systems rarely exist in nature but the nearest would be a coconut. The milk inside doesn't leak out and the thick husk protects the contents from heat and cold. Technically, there is no exchange of matter or energy with its surroundings
Energy is from the sun, which is irradiated from Earth back 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
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, along with 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 loops are active mechanisms in systems that 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
Examiner Tips and Tricks
Remember that a positive or negative feedback loop doesn't indicate whether the loop is good or bad.
In a system, a feedback loop is something that enhances or checks a process to bring the system back into balance.
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