Newly established forestry plantations are particularly vulnerable to damage by livestock and wild animals. The main problems are caused by animals that like to browse on the shoots of young plants i.e. sheep, deer, rabbits, hares and occasionally wild goats. Damage can result in stunted, forked and dead trees causing failure of a plantation which is costly to replace. Cattle will also browse young trees but can cause serious damage by trampling.
Tree species vary in their susceptibility to browsing. Sitka spruce is perhaps the most resistant of the common species planted in Irish forests, having a vigorous growth habit and strong sharp needles. Other conifers, however, such as Douglas fir and larch are very susceptible. Broadleaved species are all very susceptible and must be protected from the outset.
Depending on the species, young trees can remain susceptible to browsing for many years after planting. Repeated browsing can seriously check growth and it can take many years before trees are robust and tall enough to overcome its effects. One exception is deer damage which can also affect older trees in the thicket and pole stages. Bark stripping is a frequent occurrence where deer numbers are high causing damage to the wood quality in the lower trunk which is the most valuable part of the tree.
Existing walls or hedges are sometimes used when they are available but sheep fencing is the most common method of protecting newly planted trees against animal damage in Irish forests. Other types of fencing increasingly being used are rabbit and deer fences.
Deer fencing is essential in certain parts of the country where deer populations are high such as Wicklow. It is expensive and is only used where high value conifer species such as Douglas fir or broadleaves are to be grown.
While fencing encloses the plantation sometimes trees are individually protected using tree shelters. These are plastic or mesh tubes slipped over the newly planted tree and held in place by a stake. The greenhouse effect within the plastic tubes creates a favourable environment for the trees to grow while at the same time provides physical protection against browsing. The tree shelters come in various sizes and tall tubes (2 metres) are sometimes used to provide protection against deer. Tree shelters are particularly useful where groups of broadleaves are being established in conifer plantations as they give extra protection to these vulnerable species.