👣 Footprints
Big idea: A footprint shows how much pressure human activities put on Earth’s systems.
Footprints help us understand whether the way we live can be supported by Earth in the long term.
🌍 Ecological footprint
The ecological footprint measures how much land and sea area is needed to provide the resources a population uses and to absorb the waste it produces.
- Includes cropland, grazing land, forests, and fishing grounds
- Measured in global hectares (gha)
- 1 gha is roughly the size of a football pitch
🌱 Biocapacity
Biocapacity is Earth’s ability to regenerate resources and absorb waste.
- If ecological footprint > biocapacity → biocapacity deficit (unsustainable)
- If ecological footprint < biocapacity → biocapacity reserve
- Countries with deficits often import resources or overexploit nature
Using resources faster than nature can replace them leads to unsustainability.
🪐 Earth Overshoot Day
Earth Overshoot Day is the date when humanity has used all the resources Earth can regenerate in one year.
- After this date, we are using future resources
- The date moves earlier if consumption increases
- Shows global ecological overshoot
🔥 Carbon footprint
A carbon footprint measures the amount of greenhouse gases released by human activities.
- Measured in tonnes of CO₂ per person per year
- Linked to energy use, transport, industry, and consumption
- Higher-income countries usually have higher carbon footprints
💧 Water footprint
The water footprint measures the total amount of water used to produce the goods and services we consume.
- Measured in cubic metres per year
- Includes embedded (hidden) water in products
- Food and clothing often have very large water footprints
Products can use large amounts of water even if you don’t see it directly.
🧪 Citizen science
Citizen science involves non-scientists helping researchers collect environmental data.
- Allows large-scale data collection
- Used to track biodiversity, migration, and climate change
- Helps monitor whether Earth’s systems are being used sustainably
📝 Exam focus
- Footprints measure human environmental impact
- Ecological footprint must be compared to biocapacity
- Biocapacity deficits show unsustainability
- Carbon and water footprints highlight specific pressures
- Footprints can be measured at local, national, and global scales