Mast seeding has been shown to have both positive and negative effects on ecosystems. An example of this is the white-footed mouse. When a mast seeding event occurs, the population of white-footed mice also increases, which has been shown in turn to increase instances of Lyme disease, since these mice are hosts for ticks, the disease's primary vector. A positive effect of increased white-footed mouse population is that they prey on Gypsy moths, which are a major forest pest in the eastern United States.