Monarch butterflies are found all over the world, from the Americas to Australia and India. However, none of them travel as far as the monarchs of North America. Every autumn, millions of monarchs fly up to 4,800 kilometers from Canada and the United States to Mexico. There, the insects spend the winter in trees in the mountains. In the spring, their offspring travel back north, stopping along the way to eat and reproduce. This yearly migration is one of the most impressive in the animal kingdom, but its future is uncertain. Recently, fewer butterflies have survived their trips. People are killing milkweed plants  — monarch’s main source of food  — to make room for crops and lawns. Storms are destroying trees where monarchs spend the winter. Fortunately, over the past 60 years, thousands of people have been helping these incredible insects.