Non-native tree species in Irish forests
Humans have a pioneering history of introducing exotic plants and animals to discover and test their benefits to society. In the past when humans have travelled and settled in new countries they have taken much of their own local knowledge, skills, plants and animals with them. Humans have also been pioneering in returning from their travels with a variety of new and exotic resources to their homeland. These newly introduced plants would often prove to be useful in society for their cultivation, range of practical uses and appealing aesthetics.
Many of the foods we eat today are non-native to Ireland. Vegetables were only first cultivated in Ireland around the 8th century. Before this much of the diet was made up of berries, leaves, roots and fungi. In modern Ireland, a typical dinner can be made up of many non-native introduced foods. A dinner plate of Irish grown food consisting of Beef (e.g. Charolais cattle, native to France), Carrots (originated in Turkey), Broccoli (originally from the Mediterranean) and Potatoes (introduced from South America) with a glass of milk (Friesian cattle, native to Holland) shows us the benefits of these plant and animal introductions.
Along with the introduction of vegetables, many other plant species were also introduced in vast amounts, these include: flowers, herbs, ornamental plants, fruits and trees. Not all were suitable or had the capacity to grow in Irish climatic conditions. However in some cases, introduced plants were found to be even more productive in their new environment than in their native range. Many of these have played a huge role in providing food, shelter, clothing, medicines, paper, improving soils, environment and adding favourable aesthetic features enhancing the landscape.
Introduction of tree species
The depletion of forests in Ireland from approximately 80% of the land area (2500 B.C.) to 1% (start of the 20th century) has been largely due to the exploitation of timber, competition from agricultural enterprises and the development of human settlements. Much of the expansion of the forest area in Ireland since then (currently 11% forest cover) has been with forests of non-native tree species. The main objectives of these forests have been to develop Irish grown timber that can be used for construction, furniture or energy production, resulting in much less reliance on wood imports.
The introduction of broadleaf tree species such as Beech and Sycamore has provided quality timber which has found favour in many uses including for furniture and veneer. These tree species are also aesthetically pleasing and may be used for ornamental planting, shelter and hedging. There have also been a number of conifer tree species introduced to Ireland such as Sitka spruce and lodgepole pine, which provide a host of benefits when sustainably managed. Sustainable forestry must satisfy the needs of three key pillars: Economic, Societal and Environmental. In terms of economy, wood production provides a contribution to sustainable forest management by creating jobs, providing income for farm forest owners, funding forest management activities and providing a source of bioenergy. With only three native conifer tree species (Scots pine, Juniper and Yew), Scots pine is the only conifer that can produce a uniform clear section of useable timber for construction purposes. Therefore with a requirement for wood that is produced from a sustainably managed forest, the introduction of fast growing (productive) conifers fulfils many of the objectives including a renewable and environmentally friendly resource.
Addressing climate challenges
It is widely accepted that increasing levels of atmospheric carbon dioxide (CO2) are consequently changing the Earth’s climate. In order to avoid any irreversible changes in climate, appropriate measures are required to mitigate and sequester these elevated levels of CO2. One of the key measures recognised as having a vital role to play is sustainable forestry. Along with the oceans and soils, forests are a major component of the global carbon cycle. Current and future forests offer a major contribution to the mitigation of greenhouse gas emissions. Through absorbing CO2 from the atmosphere, forests provide storage of this in plant biomass, deadwood and harvested wood product pools. This CO2 is taken up during photosynthesis and stored as biomass accumulates. Trees absorbing CO2 from the atmosphere and transferring it into the biomass provides a cost effective and practical method for removing large volumes of greenhouse gases from the atmosphere.
One of the most efficient forest types of storing this carbon is predominantly conifer forests. The fast growing nature of conifer trees provides an efficient method of sequestering atmospheric CO2, through on site forest emissions removals (absorbing CO2), removals through harvested wood products (carbon storage within timber) and emission avoidance by substitution of fossil fuel energy (e.g. using wood instead of oil). Non-native conifer species can be highly efficient in a number of ways: Fast production of construction grade timber, long-term carbon storage (use of timber in construction projects), highly productive on poor fertility marginal soils (unsuitable for many broadleaf species) and the displacement of alternative energy intensive products (e.g. concrete, steel). There are many factors though which can influence the carbon sequestration of current and future forests. Some of these include site conditions (previous land-use), forest management activities (harvesting type, frequency of management, fertiliser), productivity of the forest (tree species, mixtures, age), changes in climate, nitrogen deposition or the threat of pest or diseases to forests. Irish forests have removed 3.6 million tonnes of CO2 equivalent from the atmosphere and have the potential (through future forest planting) to remove much more.
New forest creation
The establishment of our future forests is supported by the Department of Agriculture, Food and the Marine through the Afforestation Grant and Premium Scheme. These schemes provide a range of planting options and forest types designed to accommodate a variety of sustainable timber production and ecological objectives. These can range from commercial timber production, Native Woodland Establishment, Agroforestry to Forestry for Fibre, depending on factors such as landowners objectives and site or soil suitability. Teagasc have been at the forefront when providing research and plant material options (tree seed choice) for native and non-native tree species. Recent research projects in Teagasc include: Ash resistance to ash dieback (Development of ash tree genetic resources with resistance to ash dieback and breeding technologies), Irish Birch and Alder Improvement (Improving the genetic quality of our native broadleaf species, birch and alder for forests), Tree improvement (Provenance selection in Sitka spruce, Oak and Beech), Potential of Minor Conifer Species (Investigating the range of conifer species available for commercial forestry on marginal agricultural land in Ireland), Transformation of Sitka spruce to CCF (Adopting forest management that retains a forest cover at all times) and many others.
Forests have a major role to play in the global carbon cycle and appropriate management of forests is crucial to aid in efforts to mitigate the effects of climate change. Ireland has the potential to play a significant role in mitigating climate change through the management of current forest and the establishment of new forests. These new forests can embrace the positive benefits associated with fast growing non-natives trees to sequester carbon, provide jobs to rural communities, provide income for farmers and create new sheltered habitats for animals and plants.