Trees and forests are the greatest renewable resource on the planet, provided they are sustainably managed. Forests lose their claim to sustainability when neglected, damaged or overcut and cleared for other uses. The resultant deforestation is a major threat to biodiversity, sustainable timber supply and to the planet’s ability to meet climate change challenges.
Deforestation is still in evidence in tropical forests including the Amazon basin, where clear-cutting combined with deliberate burning, especially in Brazil, is threatening the survival of the region’s forests and communities that depend on this unique ecosystem for their livelihoods.
Most of the overexploitation that threatens tropical forests was also a feature of European forests during the 18th and 19th centuries, until the practice of sustained yield was introduced. Since then, sustained yield has been the guiding principal of silviculture – forest management – throughout Europe.
Sustained yield regulates the felling and regeneration of forests to provide a continuous supply of timber to meet society’s needs. It ensures the equilibrium between timber removed, retained and replanted to maintain the forest continuum.
European forests came under pressure as the demand for timber and food increased from the 17th century. Unsustainable timber harvesting for building, smelting and shipbuilding as well as clearances for agricultural development lasted well into the 19th century.
Sustained yield management was central to the restoration of Europe’s forests, especially from the late 19th century. It was introduced to Ireland in the early 20th century which was centuries too late to restore the Irish forest resource. Sustained yield management did preserve the few remaining woodlands and has remained as the guiding principle in Irish forestry ever since.
How successful it is in Ireland today can be judged by data provided in the National Forest Inventory (NFI). This provides key information on the annual volume increment of Ireland’s forests and the annual felling and natural timber losses (Table 1).
Net annual volume
In Ireland, net annual volume increment (the annual volume increase in forest growth after natural losses) in 2015 was 7.69 million cubic metres while timber felled amounted to 5.01 million cubic metres or 65% of net annual volume. This shows that Ireland harvests 65% of its gross annual forest volume, which is well within the scope of sustained yield.
The volume harvested versus the standing volume compares with Europe’s forests, which remove 73% of the net annual increment, according to the EU publication State of Europe’s Forest.
One of the reasons why the annual volume removed in Irish forests is lower than their European counterparts is the age structure of our forests. An estimated 40% of the national forest estate – State and private – is under 20 years of age.
Many foresters would argue that fellings, both in Ireland and Europe, should be considerably higher to maximise forest yield without jeopardising sustained yield. In theory, optimum sustained yield results in the average net annual forest increment equalling the annual harvested volume.
In practice, annual forest volume increment exceeds volume harvested in most developed countries.
While this may be due to under-utilisation, it does provide a number of safeguards. In the event of exceptionally high timber demand or forest damage due to fire, storm, disease or other agents, the forest contains sufficient wood reserves to ensure future timber supply.
Sustained yield, while still the cornerstone of good forest management practice, has been broadened to include non-wood forestry services such as recreation. This has been happening in Ireland since the 1970s when an open forest policy was adopted by the then Forestry Division, resulting in over 29m annual visits to Irish – mainly Coillte – forests today.
Today, sustained yield has been further broadened to treat the forest as a multipurpose resource. Now known as sustainable forest management (SFM), this more expansive approach includes not only timber production but also non-wood aspects.
SFM is, essentially, the wise stewardship of forests to meet present and future social, economic and environmental objectives. These three pillars of sustainable forest management, are subdivided into their component parts; from climate to forest protection and employment to health and wellbeing.
In aiming to achieve a multipurpose forestry paradigm, SFM also acknowledges the role – and voice – of all relevant stakeholders, including the public, in forest planning.
The forest owner and forester are now required to cater not only for production forestry but for a variety of other ecological and societal needs. Yet, sustained yield remains at the centre of SFM to supply present and future timber needs for construction, design and energy. It also allows tree nurseries, timber processors, manufacturers, renewable energy suppliers and downstream industries to plan well into the future.
Upcoming forestry events
Forestry events over the next few months are likely to feature as webinars until Covid-19 restrictions are relaxed.
The following are some events organised by Teagasc, The Society of Irish Foresters (SIF) and Forest Industries Ireland (FII) in association with the Wood Marketing Federation (WMF) and the Royal Institute of the Architects of Ireland (RIAI) with support from the Department of Agriculture, Food and the Marine.
Links to webinars will be advertised. Also check, www.teagasc.ie/crops/forestry, www.wood.ie and www.societyofirishforesters.ie. The Irish Timber Growers Association will also be featuring a list of webinars to be announced soon in association with the Irish Farmers Journal.
These include forestry as a land use option on the family farm, agroforestry and forest protection.