More info: White-tailed deer are the largest herbivorous animals in New Jersey, and studies show they can have a tremendous impact on their habitat.
Even at low densities, herbivores such as deer can change the composition of a forest by eliminating their own preferred food plants. Deer at high densities also impact other forest wildlife. In some cases, white-tailed deer have eliminated the required nesting cover of certain woodland birds. Excessive browsing by deer may allow exotic plants to invade forests, forcing native species to compete for survival.
When the population is in healthy numbers, deer help increase diversity in the ecosystem. As they feed on the dominant plants in the habitat, they create space for less competitive plants to have a chance.