Text and photo from a Humane Society of the United States (HSUS) article found here:
"A Yale Forestry School study of 120 study plots in six Connecticut towns across western Connecticut found that deer density is not a leading factor in tree regeneration decline or loss of plant diversity."
"It is easy to blame deer for problems with forest growth, but these many other factors contribute to these: Acid rain, insects, disease, forest fragmentation, pollution, loss of soil fertility, browsing by other animals, invasive plant species, parasitic organisms, climatic and weather extremes and development. Forest growth in deer "exclosures" (small areas fenced to exclude deer) is often pointed to as proof of deer impacts on forests, yet we must be mindful that these protected areas show us what a patch of forest might look like without any deer. Such a state is no more "natural" than deer presence in great numbers."
"We may want to see more biodiversity in certain areas because we saw it there in the past. Yet nature is not static; a forest floor carpeted with wild flowers can rapidly transition to another state as a result of forest succession. Certain plant species are shaded out as trees mature and the forest canopy closes. Later successional stages are, by their very nature, less diverse. We shouldn’t blame deer for every change."