Even-aged and uneven-aged forestry: Ecological and economic aspects
NEWS | 2012-06-13
Even-aged forestry is considered by many to promote a high timber yield, while uneven-aged forestry is seen as less detrimental to the natural values of forests. Three Finnish reviewers have now investigated the scientific support for such views.
The methods used in Swedish forestry have long been under intense debate. Even-aged forest management, which involves simultaneous harvesting of entire stands, has been highly prevalent in Sweden for half a century. Proponents of this method usually maintain that its efficiency and high timber yield makes it economically superior. On the other hand, supporters of selective felling and other forms of uneven-aged forest management point out that alternative methods of this kind can preserve natural values that clear-cutting would eliminate.Using a systematic approach, three researchers at Helsinki University in Finland have now investigated what the scientific literature has to say about the ecological and economic consequences of various felling methods. They have reviewed studies of forestry in the central and northern parts of Fennoscandia and adjacent parts of Russia.
Seven studies of the ecological effects of forestry focused on invertebrates. It emerged that such fauna is generally less disturbed by selective felling than by clear-cutting. Felling can affect animals not only directly, but also indirectly through its impact on vegetation. Only two studies compared vegetation changes after different kinds of felling, but both indicated that selective felling impacts less on undergrowth than clear-cutting, at least in the short term.
Not clear whether even-aged forestry
results in superior growth and economic performance
Studies of timber growth in forests under various kinds of management have obtained mixed results. According to six studies, uneven-aged forest stands grow more slowly than even-aged stands; but five other studies came to the opposite conclusion.
Seven studies compared different kinds of forest management in terms of economic performance. Two of these studies found that economic output was highest in even-aged forests; but according to two others, it was highest in uneven-aged forests. In the remaining studies, outcomes were dependent on, for example, climatic conditions, interest rates or the original characteristics of the forest stand.
The Finnish researchers conclude that the studies reviewed offer no straightforward support for the view that uneven-aged forestry is characterised by inferior economic performance.
This review of forest management systems, already available online, will appear in a forthcoming issue of Ambio, a journal published by the Royal Swedish Academy of Sciences.