Tree protection systems against deer in forest areas

Deer browsing is a major challenge for forest regeneration and biodiversity conservation. These herbivores, in search of food, can cause significant damage to young trees, compromising their growth and survival. Protecting trees from deer is therefore a priority for forest owners and managers of natural areas.

Understanding Deer Behavior

Before considering protection systems, it is essential to understand deer behavior and the factors that influence their food choices. Deer are opportunistic herbivores that feed on various plants, including young tree shoots. Their diet varies according to the season and the availability of resources.

Factors Influencing Browsing

• Deer Population Density: A high deer population density puts increased pressure on food resources, increasing the risk of browsing. For example, in areas where the deer population has experienced a significant increase, such as in the forests of the Gaspésie region of Quebec, browsing of young trees has increased significantly in recent years.
• Food Availability: When food is scarce, deer are more likely to feed on trees. In winter, when snow covers the ground and makes it difficult to access herbaceous plants, deer turn to trees for food.
• Attractiveness of Tree Species: Some trees, such as young oaks and maples, are particularly attractive to deer due to their high nutrient content. For example, red oak is a species highly prized by deer, which explains why it is often the target of browsing.
• Weather Conditions: Cold and snow can push deer to feed on trees to maintain their health. When temperatures are low, deer need to consume more food to maintain their energy levels.

Impact of Browsing on Forest Regeneration

Deer browsing can have significant negative consequences on forest regeneration, impacting the composition and structure of forests.

• Defoliation: The loss of leaves and buds weakens young trees, making them vulnerable to diseases and pests. For example, a young red maple whose leaves have been browsed by a deer may be more likely to contract a fungal disease.
• Mortality of Young Seedlings: Excessive browsing can lead to the death of young trees before they reach adulthood. The mortality of young seedlings is particularly high when browsing is carried out on very young trees, as they are more vulnerable to damage.
• Modification of Floristic Composition: Deer can favor the growth of certain tree species at the expense of others, thereby altering the composition and structure of forests. For example, excessive browsing of young red oaks can favor the growth of sugar maples, as the latter are less attractive to deer.

Different Tree Protection Systems Against Deer

To protect trees from deer browsing, forest owners can turn to different protection systems. These systems can be classified into three main categories: physical protection, chemical protection, and alternative methods.

Physical Protection

Physical protection consists of creating physical barriers to prevent deer from accessing trees. Fences, sleeves, and individual cages are examples of physical protection.

Fences

Fences are an effective and widely used means of protecting trees from deer. They prevent deer from accessing the protected area, providing lasting protection. Several types of fences are available, each with its own advantages and disadvantages.

• Nets: Nets are lightweight, easy to install, and relatively inexpensive. They are often used to protect young trees on small areas. However, they can be fragile and require regular maintenance, as they can be damaged by tree branches or by wild animals.
• Wire Meshes: Wire meshes are more resistant than nets and offer more durable protection. They are generally used to protect tree plantations on larger areas. However, they are heavier and more expensive than nets and require more complex installation.
• Panels: Panels are robust and durable, providing reliable long-term protection. They are often used to create fences around sensitive areas or to protect large trees. However, they are heavier and more expensive to install than other types of fences.
• Electric Fences: Electric fences are an effective deterrent for deer, preventing them from approaching the trees. They are relatively inexpensive to install and maintain, but they require regular maintenance to ensure their effectiveness. Electric fences must be properly installed and maintained to be effective.

Sleeves and Individual Cages

Sleeves and individual cages provide targeted protection to young trees, protecting them from browsing. They are generally made of plastic, metal, or biodegradable materials. The choice of material depends on the desired lifespan and the available budget.

• Effectiveness: Sleeves and individual cages are very effective at protecting young trees from browsing, especially when used to protect small trees. They offer complete and effective protection, but their cost can be high, especially if many trees need to be protected.
• Limitations: Sleeves and individual cages must be installed individually for each tree, which can be time-consuming and labor-intensive, especially if many plantations need to be protected. They can also be damaged by wild animals or by extreme weather conditions.
• Lifespan: Sleeves and cages can last for several years, but they must be replaced in case of degradation or damage. Biodegradable materials have a shorter lifespan than plastic or metal materials, but they have the advantage of being more environmentally friendly.

Individual Protection Using Natural Materials

Natural materials can also be used to protect young trees from deer browsing. This approach is often more economical and more environmentally friendly than traditional protection methods. However, it is generally less effective and durable.

• Branches: Branches can be used to create a barrier around the tree, protecting it from deer browsing. This method is simple and inexpensive, but it is less effective than other physical protection methods and may require regular maintenance.
• Leaves: Leaves can be used to cover the trunk of the tree, protecting it from deer browsing. This method is inexpensive, but it is less effective than other physical protection methods and may require regular maintenance. The effectiveness of this method depends on the density of the leaves and the ability of deer to cross them.
• Natural Textiles: Natural textiles, such as jute or hemp, can be used to wrap the trunk of the tree, protecting it from deer browsing. This method is relatively inexpensive and more environmentally friendly than plastic-based protection methods, but it is less effective than other physical protection methods and may require regular maintenance.

Chemical Protection

Chemical protection involves using chemical products to repel deer from trees. This approach can be effective in the short term, but it has significant drawbacks.

Repellents

Repellents are products that give off an unpleasant odor or taste to deer, thus deterring them from feeding on trees. They are generally applied to the trunk of the tree or on the ground. Repellents can be odor-based, taste-based, or contact-based. The effectiveness of repellents varies depending on weather conditions, deer habits, and frequency of application.

• Odor-based Repellents: They use strong odors, such as garlic, chili pepper, or peppermint oil, to repel deer. Their effectiveness may vary depending on weather conditions and deer habits. The odor may also be perceptible to humans, which may be a drawback.
• Taste-based Repellents: They use bitter or irritating products to discourage deer from eating leaves and shoots. Their effect is generally temporary and they must be reapplied regularly. They can be difficult to apply and their effectiveness may vary depending on the type of tree and the size of the deer.
• Contact Repellents: They use chemicals that repel deer when they come into contact with them. They are often used to create a barrier around trees. They may be more effective than odor-based or taste-based repellents, but they can be harmful to the environment and human health.

Anti-Herbivores

Anti-herbivores are toxic chemicals that kill deer. They are generally not used in forest areas because they can have negative consequences on the environment and human health. They can also kill other wild animals, such as birds and small mammals, that may feed on the carcasses of dead deer.

Alternative Methods

Alternative methods can be used to reduce deer browsing without resorting to physical or chemical protection. These methods are often more environmentally friendly and can be combined with other protection methods.

Planting Techniques

Some planting techniques can help reduce deer browsing. These techniques aim to create conditions less conducive to browsing or to use tree species less attractive to deer.

• Planting in Dense Groups: Deer tend to avoid dense groups of trees, as they offer less space to move and feed. Planting trees in dense groups can therefore reduce browsing. In addition, trees in dense groups protect each other from wind and cold, which can promote their growth.
• Selection of Browse-Resistant Varieties: Some tree species are more resistant to browsing than others. Choosing browse-resistant varieties can help reduce the risk of damage. For example, white pine is a tree species that is relatively resistant to deer browsing, as its needles are less attractive to them.
• Planting Non-Preferred Trees: It is also possible to plant tree species that are less attractive to deer, such as eastern white cedar or black spruce. These species have a less pleasant taste for deer and are therefore less likely to be browsed.

Deer Population Management

Managing the deer population is an effective way to reduce the browsing pressure on trees. This management can take different forms, such as hunting, capture, and sterilization.

• Hunting: Hunting is a traditional way to regulate the deer population. It must be practiced responsibly and controlled to avoid disrupting the balance of the ecosystem. Hunting can be an effective solution for reducing browsing pressure, but it can be controversial and require rigorous management.
• Capture and Sterilization: Capture and sterilization of deer are non-lethal methods of population regulation. Deer are captured, sterilized, and released back into the wild. This method is less controversial than hunting, but it is more expensive and less effective at quickly reducing the deer population.
• Habitat Reduction: It is also possible to reduce the habitat of deer by modifying the vegetation or creating areas less conducive to their presence. This method can be effective in the long term, but it can be difficult to implement and require significant management efforts.

Choosing the Appropriate Protection System

The choice of the appropriate protection system depends on several factors, such as the type of tree to be protected, the size of the trees, the planting density, the budget, and the desired environmental impact. It is important to evaluate the advantages and disadvantages of each system before making a choice.

For example, fences are effective at protecting trees from browsing, but they are expensive and can have a visual impact on the environment. Individual sleeves are more effective at protecting small trees, but they are more expensive and take longer to install than fences. Repellents can be a more economical solution, but their effectiveness is limited and they must be reapplied regularly.

It is also important to take into account the practical aspects of the installation and maintenance of protection systems. Fences and individual sleeves require regular maintenance to ensure their effectiveness. Repellents must be reapplied regularly, which can be tedious. Alternative methods, such as planting techniques and deer population management, also require ongoing management efforts.

Innovation and Research

Research and development efforts are underway to develop more effective and sustainable protection systems. New materials and technologies are being developed, as well as machine learning techniques to better understand deer behavior and adapt protection systems accordingly.

Research on natural repellents and biodegradable protection methods is also a major area of interest. Research is underway to develop plant-based repellents and biodegradable materials for sleeves and cages.

Protecting trees from deer browsing is an important challenge for biodiversity conservation and sustainable forest management. By implementing effective protection systems and promoting research and innovation, we can contribute to the preservation of our valuable forest ecosystems.