What is sustainability?
Sustainability means living in a way that can go on for a very long time. We meet our needs today and leave enough for people in the future.
The idea is often shown as three pillars (or three circles that overlap):
- Environment — clean air, water, soil, forests and wildlife.
- Society — health, education, safety and fairness for all people.
- Economy — jobs and income that let people live well.
A plan is sustainable only when it works for all three. A factory that makes jobs but poisons the river is not sustainable.
Resource use: renewable and non-renewable
A renewable resource grows back or refills: forests, fish, fresh water, sunlight, wind. It is used sustainably when we take it no faster than it renews. Cut more trees than grow each year and the forest shrinks.
A non-renewable resource does not refill in human time: coal, oil, natural gas, metal ores. To use them more sustainably we can use less, reuse and recycle, and switch to renewables (solar, wind).
The circular economy keeps materials in use: design things to be repaired, shared and recycled, so “waste” becomes a new raw material.
Ecological footprint and overshoot
The ecological footprint measures how much land and sea is needed to grow our food, give our materials and soak up our waste (mainly carbon dioxide). It is measured in global hectares.
Earth's biocapacity is how much nature can renew in a year. At present humanity uses about 1.7 times that — as if we had 1.7 Earths. This is called overshoot. We cover the gap by using up stocks: cutting old forests, over-fishing and letting carbon build up in the air.
Inequality and sustainability
Footprints are very unequal. An average person in a high-income country can use several times more resources than a person in a low-income country. India's average footprint per person is below one Earth.
Yet the harm often falls on poorer people: they live nearer to polluted rivers, dumps and floods, and have less money to adapt to climate change. This is called environmental injustice.
So sustainability also asks about equity (fairness): those who used most should cut most and help others to develop cleanly. Poverty itself can push people to over-use land or forests, so reducing poverty is part of the answer.
Sustainable spaces and the SDGs
A sustainable city has: good public transport, walking and cycling paths, green parks that cool the air and soak up rain, energy-saving buildings, waste sorting and recycling, and affordable homes for all.
In 2015 all UN members agreed on 17 Sustainable Development Goals (SDGs) for 2030, such as no poverty, clean water, clean energy, sustainable cities, climate action, and life on land and below water.
Stewardship means acting as a careful caretaker, not an owner who uses things up. Governments, companies, communities and each person share it. Many local and Indigenous communities have long practised stewardship, like sacred groves in India that protect forest patches.
Spatial technologies for sustainability
- Remote sensing: satellites photograph Earth again and again, so we can see forest loss, crop health, floods and ice melt.
- GIS (Geographic Information System): puts many map layers — land use, roads, rivers, population — on top of each other to answer questions like “Where should a new park or bus route go?”
- GPS: finds exact positions on the ground, used for tracking animals, mapping trees or planning deliveries with less fuel.
These tools help us measure change, plan sustainable spaces and check whether policies work.
Try it: your own footprint
For one week, keep a tally: how many times did you walk, cycle or take a bus versus go by car? How many plastic items did you throw away? How many meals had meat? Predict first which habit makes your footprint biggest. Then pick one change and try it the next week. In the 3D, set cutting just above growing and see how long the forest takes to vanish.
Key formulas and definitions
- Sustainable use: rate of use ≤ rate of renewal
- Three pillars: environment + society + economy
- Ecological footprint ÷ biocapacity > 1 ⇒ overshoot (today ≈ 1.7 Earths)
- Renewable: forests, water, sun, wind · Non-renewable: coal, oil, gas, ores
- Circular economy: reduce → reuse → repair → recycle
- SDGs: 17 goals agreed in 2015 for 2030
Worked examples
1. A forest has 1,000 trees and grows 50 new trees a year. Is cutting 80 trees a year sustainable?
No. 80 cut > 50 grown, so the forest loses about 30 trees a year. It would take about 1,000 ÷ 30 ≈ 33 years to disappear (sooner, as fewer trees make fewer seeds).
2. A town plans a factory by the river. Check it against the three pillars.
Economy: it brings jobs (good). Society: workers need safe conditions and the town clean water. Environment: waste must be treated before it reaches the river. Only if all three are met is it sustainable.
3. Why is recycling aluminium cans a sustainable choice?
Aluminium ore is non-renewable. Recycling uses about 5% of the energy of making new metal and saves ore and landfill space.
4. Explain how inequality affects sustainability, with one example.
Rich groups use far more resources, but poor groups often suffer the damage, such as living near polluted rivers or flood zones. Fair solutions ask big users to cut more and help poorer places develop cleanly.
5. How could GIS help a city choose where to plant a new urban forest?
Stack layers: temperature (hot spots), population density, free land, and air pollution. The best site is hot, crowded, polluted and has free land.
Common mistakes
- Thinking sustainability is only about the environment. It also needs fairness and a working economy.
- Saying renewable resources can never run out. Forests, fish and groundwater run out if we use them faster than they renew.
- Blaming only population size. How much each person uses (and who uses most) matters just as much.
- Treating recycling as the first step. Reducing and reusing save more than recycling.