Does fencing for forest regeneration pay? The short answer is "yes"--if you want a diverse and sustainable forest resource in the future. Pennsylvania's hardwood forests usually regenerate naturally after a harvest. Normally, stump or root sprouts, small seedlings and saplings, and stored seed provide the ingredients that determine the composition of the next forest. Therefore, before harvesting, you should consider the quantity, quality, and species of advanced regeneration, and the potential impact of deer browsing--perhaps the single most important factor limiting regeneration across the Commonwealth. Deer prefer to browse seedlings, saplings, and sprouts of the most valuable timber species. Recognizing and addressing a browsing problem before harvesting is critical to the successful establishment of a forest stand for the future.
If deer density is currently high or if your forest has had high deer density in the past, there may be insufficient regeneration to successfully replace trees taken in harvest (Marquis and Brenneman 1981, Jones et al. 1993). Evaluating the species composition and quantity of advanced regeneration provides one indicator of deer density. Three signs of deer damage are undesirable plant species, lack of desirable understory vegetation, or a conspicuous browse line. An unfortunate but true observation is that deer tend to prefer timber species as browse and ignore less desirable species such as striped maple, beech, and ferns. If the stand is deplete of understory vegetation, and if this depletion has been caused by deer, you may need to take measures to create advanced regeneration (understory vegetation) before a harvest, especially if your plans call for a harvest intensity that moves the stand toward regeneration.
Perhaps the most visual method of identifying a deer problem is the browse line--the tree height a deer can reach to find twigs and leaves. Vegetation missing from the lower part of trees and shrubs indicates a deer problem. Deer also eat wildflowers--the absence of some and the overabundance of others may indicate a possible deer problem. The Pennsylvania Bureau of Forestry and the Pennsylvania Game Commission have data on deer populations for your county and can help you determine whether deer are a problem.
The most effective and economical way to control and prevent deer damage is hunting. A successful deer harvesting program can minimize deer damage and foster regeneration. Along with hunting, and depending on the site, regeneration may require herbicide use to suppress unwanted grasses, ferns, and woody plants that interfere with the establishment of desirable plants. Various deer damage control methods such as repellents, tree shelters (tubes), trapping and transferring deer, or fertility control are either very expensive or unproven in Pennsylvania forests. If one is regenerating or planting trees on only a few acres, then tree shelters may prove more cost effective than fencing, but some studies suggest that shelters may inhibit growth, harbor pests, and increase diseases.¹ Other than state-regulated hunting, fencing may be the next best option for regenerating desirable tree and plant species.
¹Economic analysis shows that on five acres or less, planting 400 trees per acre, tree shelters cost less than a fence--assuming the tubes cost $2 apiece and the fence costs $2 per linear foot installed. For more than five acres, a fence becomes more cost effective. For more detail on concerns about growth rates and mortality in tree shelters, see Forest Finance 6.
For numerous reasons, private forest landowners are reluctant to fence. Fences may reduce access landowners enjoy. Fences also may be visually unpleasant and detrimental to aesthetic values. Costs, however, most likely have the greatest effect on decisions to fence. One way to rationalize fencing costs is as an up-front investment to ensure a future forest that provides a sustainable flow of timber, wildlife, and other benefits. Excessive deer browsing can create a future forest with little or no valuable timber, devoid of aesthetically pleasing and ecologically important shrubs, herbs, and wildflowers normally found in Pennsylvania's diverse forests.
Questions to consider before Fencing
When considering a fence, ask yourself the following questions:
What effect does deer browsing have on forest values?
Two types of forest values are lost to deer overbrowsing. One is the lost value of future timber products, if deer damage or destroy them at a young age. Obtaining revenues from timber or other products requires long-term commitments that often may extend beyond the owner's lifetime.
Landowners also enjoy other values such as improved wildlife habitat, recreation, and biodiversity. These so-called "amenity values" are difficult to price, but most people recognize them as important forest benefits. By assessing their objectives, landowners will determine how important these values are. In so doing, they may discover that they need to take steps to control deer browsing to achieve certain objectives.
How much does deer fencing cost?
Fencing costs depend on the type of fence, length needed, and site and installation conditions. Various fences are designed specifically to exclude deer. Most popular are high-tensile electric and woven wire fences. Table 1 compares these two fence types. Another fence type becoming more popular is the plastic variety. It is similar to the woven wire--a tightly interwoven mesh.
Table 1. Comparison of high-tensile electric wire fencing to woven wire fencing.
|Recommended height||Six to nine strands: 5-7 feet||8 feet|
|Costs (installed per linear foot)||$1.00-$1.50||$1.50-$2.50|
|Installation||Fewer posts and bracing||Requires more posts|
|Deer behavior||Learn to ignore it||More effective at keeping deer out|
|Weather||Problems with grounding - dry soils, snow||No problem|
|Topography||Better on flatter terrain||No problem|
|Human contact||Make sure fence is well posted to prevent shock||No problem|
The type you choose depends on several factors and ultimately on your preference. No fence excludes all deer. Deer learn how to get through, over, or under fences. In fact, having a few deer inside a fence is potentially beneficial if the fenced area is large enough since their selective browsing can reduce competition among some plant or tree species. Working with a knowledgeable resource professional is essential when dealing with these types of issues.
A fence has done its job when the regeneration is successful and out of reach of deer. This may require 5 to 10 years. Based solely on installation cost, the electric tensile wire fence is cheaper. It also, in principle, is reusable, perhaps an important factor if you are harvesting different areas every 5 to 10 years. You can finish establishing regeneration on one section, remove the fence, and reuse it in another section. The woven wire fence, although salvageable as scrap, is not readily reusable because of the difficulty in maneuvering it from one place to another.
The woven wire fence works better than the electric fence at excluding deer. However, as mentioned above, deer sometimes are able to jump over or go under any fence. A higher electric fence, with more strands to narrow the space between wires, may be more effective. Obviously, electric fences deter deer by shocking. The objective is to teach deer to avoid the shock and stay away. If deer learn to ignore the shock, or if there is a power loss or reduction, the electric fence's value drops. It is best to train deer early in the process.
Electric fences require continuous maintenance, which may involve weekly visits (Selders and McAninch 1987). Electric fences also require signage (indicating electrification), careful and specific installation, specialized equipment, and energizers. The options for energizers include plug-in, battery, and solar. Plug-in energizers (if the fence is close to a commercial electric source) are the most economical and require the least maintenance.
Finally, cost depends on the area fenced and the site conditions. The fewer acres you fence, the more expense is attributable to fixed costs. The costs of hauling heavy materials, establishing electrical equipment, and erecting the fence per unit length are usually fixed regardless of the area fenced. Variable fencing costs, including labor and materials, increase as the fenced area increases, but at a decreasing rate. The larger the area, the less it costs per acre protected. (Table 2 shows that doubling the area does not double the length of fencing required.) On average, deer fences in Pennsylvania enclose 20 to 40 acres.
Table 2. Linear feet of fencing required to enclose different square acreages.
|Square acres||Linear feet|
Fencing large areas may not be practical because of the terrain or the difficulty of removing deer from the area before "closing" the fence. Terrain conditions also affect construction costs. An area that needs little site preparation such as clearing obstacles is less expensive to fence. Generally, installers clear the fence perimeter of vegetation and debris before fencing to allow bulldozer, four-wheeler, or skidder travel. Also, this open buffer allows deer to better see the fence and avoid it.
Expect lower costs if the land is relatively flat, the fenced area is relatively square (fewer corners), and trees serve as posts. Your costs will be significantly lower if you self-install the fence. If you use an outside contractor, prepare the contract in writing, showing work specifications and responsibilities of each party.
How do I cover the cost of fencing?
Like any rational investment, fencing costs should return benefits. The benefits from fencing include better wild- life habitat, future timber revenues, and other forest values important to the landowner. However, fencing is a long-term investment--the financial benefits might not happen for many years. If the decision to fence is made purely for future timber revenues, you can use financial tools such as cost-benefit analysis to estimate returns from the investment.
The following example depicts how much future revenue is necessary to make the fencing investment "pay off " at different interest rates. This example uses a 20-acre square fence costing $2.00 per linear foot, installed for $7,468 (3,734 linear feet x $2). On a per-acre basis, the cost is $7,468 ÷ 20 = $373.40. Table 3 shows future timber values needed per acre to offset the upfront fencing costs of $373.40 per acre. This example ignores all future fence maintenance costs. At low interest rates and shorter rotations, less revenue from a future timber harvest pays for the fencing. Longer rotations require more future revenue to make up for the fencing costs. For example, at 80 years with a 6 percent interest rate, you must expect harvest revenue per acre of $39,504 to make the fencing investment pay off.
Table 3. Future timber revenues per acre needed to offset fencing costs of $373.40 per acre, using different discount rates and rotation ages.
|Discount rate||Rotation age (years)|
The revenues in Table 3 are for timber values only. In some cases, landowners look at fencing solely from a financial perspective and reflect on the profitability of the investment. The decision to fence, however, usually involves more than just timber revenues; it includes sustaining a forest that will provide many other benefits.
Paying for the fence is a cost of regenerating a forest. How can a landowner cover this cost? One way is to set aside some of the revenues from a timber harvest. Another way is to take advantage of the federal reforestation deduction and amortization offered to forest landowners. Deer fencing is recognized as a reforestation expense for tax purposes. Taxpayers can elect to deduct up to $10,000 of qualified reforestation expenses in the year it occurs, and amortize qualified expenditures over the $10,000. In the example in the text, the landowner would deduct all $7,468 in the year the fencing was installed.
Landowners want to see a sustainable forest on their land for many reasons other than timber income. Ensuring a future forest after a timber harvest may require an investment in fencing. The benefits of fencing include not only a stand of valuable timber, but also the many other values of a sustainable forest. Fencing is a gift to the future if timber, improved wildlife habitat, plant diversity and other benefits are a landowner's goal. Fencing costs are part of an overall forest management plan. The choice of fence type depends on site conditions, landowner preferences, and costs. The decision to fence should occur early, before the harvest and while the option to establish regeneration is still available. Deciding to harvest without considering regeneration might not produce an outcome that sustains forest values. Once the seed source is gone or deer eliminate regeneration--allowing ferns, grasses, or other vegetation to become established--fencing might be fruitless. Regenerating a forest with significant deer damage might require more expensive remedial action in addition to fences.
- Jones, S. B., D. DeCalesta, and S. E. Chunko. 1993. "Whitetails are Changing our Woodlands." American Forests.
- Marquis, D. A., and R. Brenneman. 1981. The Impact of Deer on Forest Vegetation in Pennsylvania. Forest Service General Technical Report NE-65.
- Selders, A. W., and J. B. McAninch. 1987. High-Tensile Wire Fencing. Ithaca, N.Y.: Northeast Regional Agricultural Engineering Service.
Prepared by Michael Jacobson, associate professor of forest resources.