Cars and other motor vehicles use oil to power them. Oil is a natural resource - a substance that the Earth produces naturally. We pump oil out of the ground using enormous machines, turn it into petrol and sell it at garages. Over one-third of the world's oil production every year is burned in the engines of motor vehicles. However, if we keep on using this natural fuel as much as we do now, it will eventually run out. Because it is an important part of the Earth, this would cause a lot of damage to the environment.

If we all rode bikes, this would obviously help. However, a lot of people make a lot of money from making and selling petrol, oil and cars. If we all rode bicycles, they would all lose their jobs. Think of all the people who work in garages selling cars and petrol, and all the people who work in factories making cars. What would they do if we all rode bikes?

Most of the oil in the world comes from countries in Asia like Saudi Arabia and Kuwait. If we all rode bikes, we wouldn't need their oil any more. What would the people who produce oil in these countries do then? How would they earn a living?

So while using less oil would be good for the environment, using none at all would mean that a lot of people would lose their jobs. Which is worse? Damaging the environment or lots of people losing their jobs? It's not easy to decide, is it?

There are other problems with everyone riding bikes. Have a look at Ups and downs to find out more.