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Issue: Deer Abundance

White-tailed deer directly affect many aspects of our lives.  Hunters, farmers, foresters, motorists, gardeners, and homeowners are all impacted by deer abundance levels.  This may be through car deer collisions, disease transmission, loss of desirable landscaping, crop damage, or over-browsed woodlands. 

Reducing the impact of deer on forest ecosystems is imperative to sustainable management of our forest resources.  Over-browsing by deer can change the composition of the forest.  The kind of young trees and their abundance is affected by deer.  For example, ecologically and economically important species like oaks are greatly reduced or eliminated from the understory.  If deer are too numerous, mature forests will have no or very few desirable tree seedlings to replace trees that are harvested or die of natural causes.  Research has shown that as many as 85% of forested sites in Pennsylvania that are harvested fail to regenerate a new forest of desirable tree species due to over-browsing by deer.  

Over-abundant deer populations also reduce the diversity of plants and other wildlife species found in the forest.  High levels of browsing by deer can completely remove the shrub and tree seedling layers in a forest.  Many native wildflower species are also preferred deer foods.  These plants are also reduced in abundance or completely eliminated when deer impact is high.  With the loss of the understory tree and shrub layer comes a loss in abundance of many other wildlife species.  Numerous species of birds which nest in the shrub layer or on the forest floor are reduced in abundance when deer populations rise beyond what the habitat can support. 

When deer populations are above the carrying capacity of the land for long periods of time they begin to degrade their habitat.  Under these conditions, forest understories become composed predominantly of plants that deer avoid or prefer not to eat.  Once this happens, the degraded environment supports only a fraction of the biodiversity it once did.

For More Information see the publication  entitled Impacts of White-tailed Deer Overabundance in Forest Ecosystems: An Overview (written by Thomas Rawinski of the U.S. Forest Service, State and private Forestry section).