听一分钟英文：Population-人口（在线收听）

The world’s population is getting bigger and bigger. There’s a population explosion in some countries. I’m not sure if this is good or bad. The Earth can only support a limited number of people. One day, the world’s population will be too big to feed everyone. When that happens, we’ll have food wars and water wars. Many years ago, the population was controlled by famines, a shorter lifespan, disease and other natural causes. We are richer now and so we can control how long we live. This is already causing problems in some countries. Japan, for example, has almost more retired people than working people. This means workers can’t make enough money to look after old people.