Feedback Loops
A feedback loop happens when a change in a system causes effects that feed back into the system and cause more change.
Think of a feedback loop as a loop where the result becomes the cause.
Negative Feedback Loops (Stabilising)
A negative feedback loop reduces change and helps keep a system stable.
- Body temperature: too hot → sweating → body cools down
- Predator–prey populations: more prey → more predators → prey numbers fall
Exam tip: Negative does NOT mean bad. It means the system resists change and stays balanced.
[Diagram: feedback-loops] - Available in full study mode
Positive Feedback Loops (Amplifying)
A positive feedback loop makes the original change stronger and pushes the system further away from balance.
This happens because the effect of the change feeds back and causes even more of the same change.
Ice melt example (easy to picture)
- Ice melts due to warming
- Dark ocean or land underneath is exposed
- Dark surfaces absorb more heat than ice
- More heat causes even more ice to melt
Because melting ice leads to even more melting, this is a positive feedback loop.
Population example
- Population begins to decline
- Fewer individuals means fewer breeding pairs
- Fewer births occur
- Population declines faster
Exam tip: Positive does NOT mean good. It means the change is amplified.
One-sentence exam definition
A positive feedback loop occurs when a change in a system causes effects that increase the original change.
🏨 Tourism Multiplier Effect
What is it?: The tourism multiplier effect is a positive feedback loop in human systems where tourism growth feeds back to create even more tourism growth.
How it works:
- More tourists visit an area
- Tourists spend money on hotels, food, and activities
- Local businesses grow and hire more workers
- Workers earn money and pay taxes
- Government uses taxes to build better roads and facilities
- Better infrastructure attracts even more tourists
- Cycle continues — tourism causes more tourism
This is positive feedback because the output (more tourists) feeds back to amplify the input (tourist attraction).
Why it matters for sustainability
The tourism multiplier can have both positive and negative effects:
✅ Benefits
- Creates jobs and income
- Funds conservation efforts
- Improves local infrastructure
- Can protect wildlife as an economic asset
❌ Problems
- Increased demand on water and energy
- Habitat destruction for buildings
- More waste and pollution
- Can displace local communities
Positive feedback loops can spiral out of control — tourism growth without limits can damage the environment it depends on.
Learn what examiners really want
See exactly what to write to score full marks. Our AI shows you model answers and the key phrases examiners look for.
💰 Economic Inequality Feedback
Economic inequality is another example of positive feedback in human systems:
- Wealthy people have money to invest
- Investments generate more income
- More income allows even more investment
- Wealth grows faster for those who already have it
- Gap between rich and poor widens over time
Without intervention (negative feedback like taxes or regulations), positive feedback loops keep amplifying.
📝 How to explain feedback loops
When explaining any feedback loop, follow these steps:
- Identify the starting change — what changed first?
- Follow the chain of effects — what did that change cause?
- Show the loop closing — how does the effect feed back to the start?
- State the type — does it stabilise (negative) or amplify (positive)?
🧠 Quick definitions to remember
Positive feedback: A change causes effects that increase the original change.
Negative feedback: A change causes effects that reduce the original change.
Multiplier effect: When growth in one area creates growth in connected areas, which feeds back to create even more growth.
📋 Summary: Positive Feedback Examples
- Ice-albedo — melting → darker surface → more heat → more melting
- Population decline — fewer animals → fewer births → faster decline
- Eutrophication — nutrients → algae → death → more nutrients
- Tourism multiplier — tourists → investment → better facilities → more tourists
- Economic inequality — wealth → investment → more wealth
📋 Summary: Negative Feedback Examples
- Body temperature — too hot → sweating → cooling → back to normal
- Predator-prey — more prey → more predators → fewer prey → fewer predators
- Blood sugar — high sugar → insulin released → sugar drops → back to normal
⚖️ Stability and Equilibrium
Stable (Steady-State) Equilibrium
A stable equilibrium is like balancing on a bike — small adjustments keep you upright.
🎯 The Key Idea: Inputs = Outputs → the system stays stable (even if small changes happen)
- 🌡️ Body temperature: sweating when hot, shivering when cold
- 🌲 Mature forest: trees die and new trees grow → overall size stays similar
⏰ Feedback Delays
A feedback delay means cause and effect do not happen immediately.
⚠️ Why Delays Cause Problems: Because changes are delayed, people often overcorrect. This can cause the system to <u>oscillate</u>
Example: heating is turned up → room heats slowly → too much heat builds up → heating is turned off → room cools too much → the cycle repeats.
- 🐰🦊 Predator–prey cycles: prey numbers rise first, predators increase later
- 🏭 CO₂ emissions may fall now, but climate effects appear decades later
🎢 Tipping Points
A tipping point is when the system can no longer return to its original state.
🚨 Why Tipping Points Matter: Small change → positive feedback → rapid system shift
[Diagram: tipping-point-simulator] - Available in full study mode
Before tipping point
- 🏞️ Clear lake
- 🌳 Healthy forest
- 🧊 Arctic ice cover
After tipping point
- 🟢 Algal bloom → murky lake
- 🏜️ Forest dieback
- 🌊 Ice-free ocean
📝 IB Exam Tip: Positive feedback loops push systems toward tipping points. After crossing one, the system settles into a new (often worse) equilibrium.
Never wonder what to study next
Get a personalized daily plan based on your exam date, progress, and weak areas. We'll tell you exactly what to review each day.
Causal Loop Diagrams
What is a causal loop diagram?
A causal loop diagram shows clear cause → effect relationships.
It helps us see whether a change is controlled (balanced) or <u>amplifies</u>.
[Diagram: causal-loop-diagram] - Available in full study mode
Parts of a causal loop diagram
- Variables
- Arrows → show which variable affects another
- + (positive relationship) → both variables change in the same direction
- − (negative relationship) → variables change in opposite directions
- Feedback loop
+ and − do NOT mean good or bad. They only show how change happens.
How to answer exam questions using causal loop diagrams
- Name the variables
- Follow the arrows
- Explain the + or − relationships
- State whether the loop is balancing (B) or reinforcing (R)
Exam-ready summary (memorise)
- Causal loop diagrams show cause and effect
- + means variables change in the same direction
- − means variables change in opposite directions
- Negative feedback (B) stabilises systems
- Positive feedback (R) <u>amplifies</u>
- Positive feedback can cause tipping points