Yellowstone National Park, with its plentiful food and wide-open spaces, is an ideal habitat for wolves. For many years, though, wolves were banned from the park. The U.S. government thought wolves did more harm than good. Fortunately, the government rethought its decision, and the ban was lifted. Returning wolves to Yellowstone was the right decision for several reasons. In the early 1900s, the U.S. government started a program to control predators in Yellowstone National Park. The government believed wolves and other predators destroyed other park wildlife. Farmers and ranchers supported the program. They said wolves threatened their livestock. To control predators, hunters killed them. By 1926, the last Yellowstone wolf pack had been killed. For decades after that, only a few solitary wolves were sighted. In the 1960s, scientists began to focus on protecting nature rather than controlling it. They wanted to bring wolves back to Yellowstone. Many years later, it happened. By late 2014, there were 104 wolves at the park. As scientists have long realized, wolves improve biodiversity. Biodiversity is the number of species in an ecosystem, or environment. A healthy ecosystem has many different species. When wolves disappeared from Yellowstone, other animals were affected. Elk, wolves' favorite food, multiplied. Elk eat willow trees. Soon, the elk were eating more and more trees. Beavers use willows to make their homes, called dams. Because the elk ate so many trees, beavers didn't have enough wood to build dams. Beavers began to disappear from the park. Then the wolves returned. They began to eat elk. Willows grew back. Beavers returned to the park. As a result, biodiversity improved. Daniel Licht is one of many scientists who believe wolves help Yellowstone. "We have these ecosystems that are in dire need of wolves," said Licht. He thinks wolves should be returned to other habitats, too. "The pros, the benefits, would far outweigh the negatives," he said. Bringing wolves back to Yellowstone has helped in another way. Wolves bring ecotourists to the park. Ecotourists are people who travel to see nature. Ecotourists come from around the world to see Yellowstone's wolves. A 2006 study found that ecotourists spend millions of dollars in and around the park area each year. Some of that money goes to restaurants and hotels. In other words, wolves help people pay their bills. That's a good thing! The return of wolves has been important for a third reason. It has helped prove that wolves and people can live together in peace. No wolf has attacked a human at Yellowstone. And studies show that only a tiny percent of livestock die from wolf attacks. The "big, bad wolf" is a myth. Wolves belong at Yellowstone. Now that they're back, nature is in balance. Tourism is up, too. Predators such as wolves always bring some dangers. However, the good they do far outweighs the risks. Welcome back, wolves!