A natural resource is anything found in nature that living things can make use of. Water, air, soil, rock, minerals, forests, animals and plants are all natural resources, and so are coal and petroleum. Everything available in nature is a natural resource, which is why the textbook calls them a gift of nature to living beings.
A resource is not a thing, it is a use
Here is something the word hides. Nothing in nature is born a resource. Sand lay on riverbanks for millions of years being nothing to anybody, until people worked out how to melt it into glass and mix it into concrete. Petroleum sat underground doing nothing at all until engines were invented. A thing becomes a resource on the day somebody finds a use for it, and not before.
This is worth knowing because it explains something that would otherwise be puzzling. The list of natural resources keeps getting longer, not because nature keeps producing new material, but because people keep finding new uses for material that was always there. It also gives a fair warning. A resource nobody values today may be the one a country depends on in fifty years.
The first way of sorting: from living or from non-living
Natural resources can be sorted into biotic and abiotic. Biotic resources come from living things. Forests, crops, animals, fish and all the wood, food, fibre and medicine they give us are biotic. Abiotic resources come from non-living things. Air, water, soil, rock, metals and minerals are abiotic. The test is simple: ask whether it was alive, or came from something that was alive.
Coal and petroleum sit awkwardly in this sorting, and it is worth knowing why rather than being caught out by it. They are grouped with minerals because that is where they are found and how they are dug out. But they were made from living things. Coal is the squashed remains of forests that grew and were buried tens of millions of years ago, and petroleum comes from tiny sea creatures buried in the same way. That is exactly why they are called fossil fuels. A fossil is the trace of something that was once alive.
The second way of sorting is really about a clock
The second sorting is into renewable and non-renewable, and this is the one that matters. Most students memorise the two lists and stop there. Do not stop there, because the lists make no sense until you see what is really being measured.
Take firewood and coal. Firewood is renewable and coal is not. Now ask what firewood and coal are actually made of. Both are the remains of plants. Coal is simply what happens to buried plant matter after tens of millions of years of heat and pressure. They are close relatives, almost the same material. So the difference between renewable and non-renewable is not what the substance is. It is how long nature takes to make another one.
A tree takes twenty or thirty years. Coal takes tens of millions. Same starting material, two completely different clocks, and the clock is what decides the name.
| Resource | How nature replaces it | Roughly how long | Which group |
|---|---|---|---|
| Water | The water cycle. It evaporates, forms cloud, and falls again as rain | Days to weeks | Renewable |
| Air | Green plants take in carbon dioxide and give out oxygen, all the time | Continuous | Renewable |
| Forest | Seeds germinate and trees grow back | 20 to 50 years for useful timber | Renewable |
| Soil | Rock breaks down slowly and dead plants and animals rot into it | Roughly a century for one centimetre | Renewable, but only just |
| Coal | Buried forests squashed under heat and pressure | Tens of millions of years | Non-renewable |
| Petroleum | Tiny sea creatures buried and changed in the same way | Tens of millions of years | Non-renewable |
| Iron and copper ore | Formed inside the Earth by processes we cannot copy or hurry | Hundreds of millions of years | Non-renewable |
Read the third column on its own and the two groups sort themselves. Anything nature can replace inside a human lifetime is renewable. Anything that takes longer than any country can wait is non-renewable. Nobody had to decide the lists. The clock decided them.
Renewable does not mean unlimited
This is the single most misunderstood sentence in the whole unit, so read it slowly. Renewable does not mean you can take as much as you like. It means the resource comes back if you give it time to come back.
Picture a water tank with a tap running into it. As long as you draw out less than the tap puts in, the tank never empties, no matter how many years you keep drawing. Draw out more than the tap gives, and the level starts to fall. It falls slowly at first and you may not notice for a long time, but no tap in the world can save a tank that is being emptied faster than it is filled.
A forest is that tank. Cut it slower than it grows and it lasts forever. Cut it faster and it disappears, and once the soil has washed off the slope it may never return at all. The same is true of fish in a river and of grass on a pasture. This is why the word renewable is a description of speed and not a promise of safety. Hold on to it, because the next topic is about what happens when that speed is ignored.
With a renewable resource, a mistake can be repaired. Stop cutting and a forest grows back, and a village that gives a hillside twenty years can have its trees again. With coal, petroleum or copper there is no such second chance. Every kilogram burnt or used is gone for as long as anybody reading this will be alive, and for a great many generations afterwards. That is the whole reason people work so hard on sunlight, wind and water power. Those three arrive again tomorrow morning whether we use them today or not.
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