A number of aspects of our environmental situation are similar to the bacteria's situation in this story.

For example, the human population of the world has doubled twice in the past hundred years. Energy consumption is doubling about four times faster than that, and the number of automobiles in the world is doubling ten times faster than population.

These are just a few examples. Any time you hear that something is increasing by a percentage -- say, 5% per year -- that means it's growing exponentially.