Actually, fires are a natural part of the ecological cycle, and their role is not just destructive, but also creative. That's why the "let it burn" policy is fundamentally a good one, even if it sometimes causes fires on the scale of the 1988 Yellowstone fire. Let's look at what happened after the '88 fire.

First, vegetation. As you might imagine, scorched areas were in time colonized by new plants. As a matter of fact, the plant life in Yellowstone became more diverse, because the fire created an opportunity for certain plants that could not grow otherwise. For example: areas where the trees had been destroyed by the fire could now be taken over by smaller plants that needed open, unshaded space to grow. And another example: seeds of certain plant species won't germinate unless they're exposed to very high levels of heat, so those plants started appearing after the fire as well.

It's a similar story with the animals. Not only did their populations recover, but the fire also created new opportunities. For instance, the small plants that replaced trees after the fire created an ideal habitat for certain small animals like rabbits or hares; and when the rabbits and hares started thriving, so did some predators that depended on them for food. So, certain food chains actually became stronger after the fire than they were before.

And last, fires like the '88 Yellowstone fire would be a problem for tourism if they happened every year; but they don't. It was a very unusual combination of factors that year—low rainfall, unusually strong winds, accumulation of dry undergrowth—that caused the fire to be so massive. This combination has not occurred since—and Yellowstone as not seen such fires since 1988. Visitors came back to the park the next year and each year after that.