Although beautiful animals, deer are an ugly problem at Saint John's Abbey Arboretum since there are no natural predators to keep their population in check. The overpopulation in the forest has devastated ground layer plants and oak regeneration.
In the prairie, the plant diversity inside a 4-year old deer exclosure is nearly 3 times greater than outside the fence. Several deer exclosures set up throughout the Arboretum have produced similar results.
Deer prefer certain rare wildflowers and trees over others much like we prefer pizza over liver. The result is an unhealthy and less diverse ecosystem.