As more and more land is used for growing crops and grazing animals in Mexico, more trees are cut down, even in the mountainous state of Michoacan, where the monarchs migrate in the winter months. They hibernate in oyamel fir trees and, with increased cutting of these trees, monarchs have no place to spend the winter. Causes and Processes of Deforestation shows that deforestation has been taking place and has been tracked since the 1850's. There are several interrelated causes including increased population, agriculture cattle raising, and over consumption in the more developed parts of North America.
People living in the area live by exploiting the forests.
They sell the wood and use the cleared land for raising crops. It is very difficult to protect the forests in the face of these forces but also important. Deforestation threatens the wintering sites for monarchs and the corridors through which they pass as they migrate between Mexico and Canada. Monarch butterflies are just one species. This is the greatest source of genetic diversity on earth.