On Tuesday, January 6, I attended the Harrisburg conference entitled "The Challenge of Overabundant Deer in Pennsylvania." It was quite a turnout with 460 attendees from 170 organizations. They had to turn 20 people away. That alone tells you what an issue the deer population in this state has become. Why all this attention to the deer population?
The overabundance of deer is considered to be the major ecological problem in Pennsylvania. The herd has reached a size that is double what biologists feel the state can safely support. In different terms, the deer are at a population level that is more than twice the carrying capacity. It is believed the state can support a herd of 600,000 in good health. That's the carrying capacity - 600,000. Anything beyond that begins to destroy the range. The herd at the beginning of the fall season in 2003 was somewhere around 1.6 million by the best estimates give or take a hundred thousand. What are the consequences of a deer herd so far out of balance with the land?
It will come as a surprise to many people that our forests in Pennsylvania are dying due to deer browsing. This is not an easy thing to recognize. Dr. Gary Alt, the former state bear biologist, who is now assigned to manage the deer herd, with a Ph.D in wildlife ecology, openly admitted at the conference he did not notice the damage to the forest until one of the land managers in the Game Commission pointed it out to him. If deer damage to the forest is so subtle that it can escape the attention of a Ph.D in wildlife ecology, there is little chance that the general public will recognize it. Indeed, this deterioration of our forests has escaped notice of landowners, hunters and nature lovers alike. Once you know what to look for, the damage to our forests is clearly evident, but convincing the public that the damage is there and should be halted might be more challenging than controlling the herd size itself.
Forest injury can be very subtle and every woods is different with varying degrees of damage. One has to consciously look to notice the lack of tree seedlings in the understory and only a few shrubs. The absence of wildflowers is all too obvious except where the deer can't reach them - on steep slopes and cliffs. Most of our native shrubs are gone except those the deer do not like to eat, such as spicebush. The understory in many woods is nearly a pure stand of spicebush. Viburnum, hobblebush, hazelnut, buffalo-nut, huckleberry, winterberry holly, etc. are usually absent.
As the understory becomes over grazed the stage is set for ferns to spread without competition. Once ferns get established, their massive root systems keep other plants from germinating, particularly tree seedlings. This is a repetitive scene in many parts of the state. The Allegheny National Forest is over-run with fern. Likewise, ferns are widespread and dense in many areas of Forbes State Forest. Hay-scented fern at Fern-cliff Peninsula in Ohiopyle State Park has replaced buffalo-nut in the past decade and the wildflowers in the woods have disappeared. The exciting botanical field trips to Fern-cliff Peninsula in the 1980's are a thing of the past.
People see the ferns, which are luxuriant and beautiful, and think this is normal. Foresters have even received letters from the public complimenting them on their fine stewardship when in fact the forest is dying. When the standing timber is gone, there is nothing to replace it. It will take years to regenerate the forest.
Some woods are in a slightly different situation. There is some tree regeneration, but only those species that deer don't like to eat. Deer are very selective feeders until they reach starvation, then they eat anything. Oak, hickory and sugar maple forests are being replaced with birch, black cherry, locust, striped ample and sassafras. These species, with the exception of black cherry, have little commercial value and there will be no mast crops to provide food for deer, turkey, bear or squirrel. Acorns, hickory and beech nuts are the mainstay of much of our forest wildlife.
Overbrowsing the woods also seems to pave the way for invasive species. As the deer herd in our state grew, invasive plant species began penetrating our woodlands. Multi-flora rose and Japanese knotweed are the two most serious invaders. Garlic mustard, privet hedge, and Japanese barberry are other species that are also well established and outcompeting native plants.
Proof that excessive deer browsing is related to invasive species came from Fox Chapel. Biologists erected deer fencing around the trillium beds that had all but disappeared from deer herbivory. Not only did the trillium return, but the garlic mustard that had replaced them got pushed out.
Deer also compete with many other forms of wild life that depend on the forest understory for cover. As a result populations of ruffed grouse, ovenbirds, rabbits, wood thrush and Kentucky warblers are down.
Deer lovers should take note that this over-browsing of the range is harmful to the deer themselves. Their food supply grows smaller each year as unpalatable and invasive species move in to replace the plants that are more nourishing for deer. They are not finding enough to eat when they feed on the poisonous plants around your house such as rhododendron, azalea and yew.
The solution is to reduce the size of the herd, but this is no easy matter, particularly in the suburbs. The next essay on this subject will discuss the possibilities.
