Forests Protection and Health

Forests are subject to numerous threats that can potentially damage their health. Non-living factors such as strong winds and fires can devastate forests while living factors such as insect pests, diseases and animal damage can seriously undermine their health and productivity. Forest protection is therefore a primary objective of effective forest management to ensure their continued sustainability. Outlined below are some of the most common threats that impact on Ireland’s forests (Forestry Focus, n.d.):

Windthrow

Ireland's location on the periphery Western Europe and at the edge of the Atlantic Ocean results in it experiencing some of the windiest and wettest weather in Europe. Irish forests are regularly impacted by high winds and when these are accompanied by heavy rainfall, forest stability can become threatened. Windthrow, of all the potential damaging agents, is perhaps the largest threat to forests and economic forestry nationally.

Fires

Ireland does not experience the large scale forest fires that are prevalent in drier regions. Its mild moist climate ensures that prolonged droughts are very rare. Whilst fires in mature forests seldom occur, younger plantations are vulnerable to fire especially during late spring and early summer when dead ground vegetation accumulated during the previous season begins to dry out. Burning gorse and heather on hills to provide new growth for livestock also poses a major threat to forests. These fires can often get out of control, particularly during dry and windy weather, and affect plantations. Approximately 450 ha of forest are lost to fire each year in Ireland.

Frost Damage

In Irish forests frosts that occur at the end of spring and start of autumn are the most damaging. Young trees are prone to frost damage from the early seedling stage until they reach a height of approximately 1.5 – 2 metres. Trees come into leaf in spring when they have experienced a certain accumulated temperature. This process ensures that warm days do not force the trees to come into growth too early in the season. Native species are generally well adapted to the climatic conditions in Ireland and, with their growth and dormancy cycles synchronised with the seasons, they tend to avoid unfavourable weather conditions. Exotic or non-native species, however, are adapted to climatic conditions that occur in their native habitat. Moving them to Ireland may alter their growth pattern leaving them vulnerable to damage from frosts and winter weather.

Insect Pests

Irish forests are recognised under the European Union Plant Health Directive 77/93/EEC as being amongst the healthiest in Europe, with relatively few serious forest pests or diseases. This is mainly due to Ireland’s island status, the relative newness of forest estates, and the enforcement of forest plant health regulations. However, species composition of Ireland’s largely ‘man-made’ forests, which are comprised mainly of exotic conifers, makes them increasingly vulnerable to introduced harmful organisms. To date there have been few outbreaks of destructive insect pests from abroad but the increasing transportation of forest plants and wood products (e.g. logs, sawn timber, pallets, packing wood) between countries increases the risk of potentially very damaging forest pests and diseases spreading to Ireland.

Diseases

Ireland has relatively few diseases that affect European mainland forests. Its island status, its location on the periphery of Europe, and the fact that most of our forests have been established over the past 70-80 years on bare land with introduced non-native tree species, has helped to ensure our forests are largely disease free. While there are many fungal organisms present in Irish forests few cause economic damage. This situation may change in the future with the increased movement of people and plant materials, but perhaps more serious are the impacts of climate change which may generate more favourable conditions for the spread of diseases.

Animal Damage

Newly established forestry plantations are particularly vulnerable to damage by livestock and wild animals. The primary problems are caused by animals that prefer to browse on the shoots of young plants i.e. sheep, deer, rabbits, hares and occasionally wild goats. Animal damage can result in stunted, forked and dead trees causing failure of a plantation, which is costly to replace. Cattle can graze on young trees but can also cause significant damage by trampling.

Deer can cause serious damage to young plantations but they can also affect trees in mature plantations. For instance, bark stripping of tree trunks is a common occurrence where deer numbers are high. Similarly, the grey squirrel can also cause severe damage to broadleaved plantations through stripping bark on branches and main stems. The spread of the grey squirrel is a serious concern to both foresters and nature conservationists, and research is ongoing to assess the spread of species to improve strategies for effective control of animals.

Invasive Species

Invasive non-native species introduced into Ireland are of increasing concern to ecologists, land managers and fishery biologists. Introduced species and genetic material can have a significant impact on biodiversity in forests. When non-native species become invasive they can transform ecosystems, and threaten native and endangered species. The number of alien species that currently impact Irish forests are relatively few but their impact can be significant locally.

Climate Change

In the coming century, climate change in Ireland is predicted to result in warmer, drier summers in the south and east, and wetter winters and more intense storms with higher wind speeds. The frequency of extreme climatic events is also expected to increase. Each of these effects are likely to have an impact on our forests and will create many challenges for Irish forestry.