Definitions – Old-Growth/Primeval/Virgin?

The romantic idea that forests were totally unimpacted by humans until a few centuries ago is a misconception, at least for Europe. When defining a forest like primeval, pristine or virgin, authors have often claimed those forests were never subject to human impact, although this approach may be misleading. Indeed humans have existed for hundreds of thousands of years and had a great potential impact on forest ecosystems at least since they started to use fire, more than 200.000 years ago. Nowadays, indirect impacts, such as the increase in greenhouse gases or in nitrogen deposition, have also become particularly pervasive, with repercussions on forest processes and patterns worldwide. For these reasons, forests totally unimpacted by man are unlikely to exist, although few stands in remote areas may approach this condition.

Several overlapping concepts have been used to describe original, natural or near-natural woodland, and this has been a severe source of misunderstanding.  Terms such as virgin or old-growth forests have sometimes been used ambiguously. Besides, a plethora of other terms were also used, such as natural, pre-settlement, primary, primeval, pristine, relict forests and others, and diversity of languages adds to this complexity.

A Jungle of Words – From: Ancient Forests in the Northern Mediterranean: Neglected High Conservation Value Areas – WWF report – 2013

The Third Expert Meeting on Harmonizing Forest-related Definitions, organized in Rome in January 2005, tackled the problem of the ambiguous use of forest-related definitions in various international processes. The overall goal of this meeting was to improve communication and understanding of forests among stakeholders and to contribute to the harmonization of definitions related to forest resources and management for various purposes.

On the basis of this reasoning, 14 mutually exclusive levels of forest naturalness were proposed in order to incorporate the most logical and generally accepted parts of existing definitions (Buchwald 2005).

Forest Naturalness - The hierarchy of definitions proposed by Buchwald

Forest Naturalness – The hierarchy of definitions proposed by Buchwald

The first work package of FORESTS and CO, focuses on the so-called Primary Forests (which are included in the n10-n5 interval in Buchwald’s scheme). I report here a synthesis of the definitions relevant for this project but I refer the reader to the original paper for more details:

Primary forests (n10-n5): Relatively intact forest areas that have always or at least for the past sixty to eighty years been essentially unmodified by human activity. Human impacts in such forest areas have normally been limited to low levels of hunting, fishing and harvesting of forest products, and, in some cases, to historical or pre-historical low intensity agriculture.

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n10 Ultimate degree of naturalness – Primeval Forest – Forest ecosystems never modified by modern man/civilization even indirectly, where the degree of impact on the ecosystem by indigenous people has not been significantly higher than the impacts of natural wildfire and of large wild animals (e.g. beaver or megaherbivores). The fauna includes a rich host of large animal species and is not significantly affected by human-induced extinctions or changes to animal population densities. Size is landscape-scale. […]

n9 Extremely high degree of naturalness – Virgin Forest – Forest ecosystems virtually unmodified by man, and where the degree of former human impact on the forest – including soil and hydrology – has been only slightly more significant than the impacts of wildfire and animals (e.g. beaver or megaherbivores), and is no longer obvious. Wildlife inhabits the area with a fairly natural density and species composition including large herbivores and carnivores. Size is forest-scale. […]

n8 Very high degree of naturalness – Frontier forest – A frontier forest is an area meeting the following criteria: it is primarily forested and predominantly consists of indigenous tree species. It is big enough to support viable populations of all indigenous species associated with that forest type […] even in the face of the natural disasters – such as hurricanes, fires, and pest or disease outbreaks – that might occur there in a century. It is home to most, if not all, of the other plant and animal species that typically live in this type of forest. Its structure and composition are determined mainly by natural events, though limited human disturbance by traditional activities of the sort that have shaped forests for thousands of years -such as low-density shifting cultivation – may be acceptable. As such, it remains relatively unmanaged by humans, and natural disturbances (such as fire) are permitted to shape much of the forest. In forests where patches of trees of different ages would naturally occur, the landscape exhibits this type of heterogeneity. (Rearranged/shortened from World Ress. Inst.:http://www.wri.org/ffi/lff-eng/).

n7 Very high degree of naturalness – Near-virgin forest – Forest ecosystems (forest scale) untouched long enough to have attained structures, dynamics and species composition similar to virgin forest, even though they may have been significantly modified, e.g. by clearcutting or agriculture at some time in the past. They are distinguished by a mixture in time and space between different seral stages, e.g. between old-growth stages and younger stages. Human impact on the forest structures is not obvious to see. The time necessary in untouched development before this level can be reached depends on how modified the situation was at the start. It is at least several hundred years if the starting point is a plantation-like forest.

n6 High degree of naturalness – Old-growth forest – Ecosystems (stand scale) distinguished by old trees and related structural attributes. Old growth encompasses the later stages of stand development that typically differ from earlier stages in a variety of characteristics which may include tree size, accumulations of large dead woody material, number of canopy layers, species composition, and ecosystem function. The age at which old-growth develops and the specific structural attributes that characterise old-growth will vary widely according to forest type, climate, site conditions, and disturbance regime. […] However, old-growth is typically distinguished from younger growth by several of the following attributes: 1) large trees for species and site, 2) wide variation in tree sizes and spacing, 3) accumulations of large-size dead standing and fallen trees that are high relative to earlier stages, 4) decadence in the form of broken or deformed tops or bole and root decay, 5) multiple canopy layers, and 6) canopy gaps and understory patchiness. Old-growth is not necessarily “virgin” or “primeval.” Old-growth can develop following human disturbance […]

n5 Quite high degree of naturalness – Long untouched forest – Relatively intact forest (stand level) that has been essentially unmodified by human activity for the past sixty to eighty years or for an unknown, but relatively long time. Signs of former human impacts may still be visible, but strongly blurred due to the decades without forestry operations. The time limit depends on how modified the forest was at the starting point. […]

 

Suggested Readings:

Buchwald, E., 2005. A hierarchical terminology for more or less natural forests in relation to sustainable management and biodiversity conservation, Proceedings: Third expert meeting on harmonizing forest-related definitions for use by various stakeholders Food and Agriculture Organization of the United Nations, Rome, 17-19 January 2005.

FAO, 2005. Proceedings: Third Expert Meeting on Harmonizing Forest-related Definitions for Use by Various Stakeholders. Food and Agriculture Organization of the United Nations, Rome.

Mansourian, S., Rossi, M., Vallauri, D., 2013. Ancient Forests in the Northern Mediterranean: Neglected High Conservation Value Areas., Marseille, France, p. 80.

Peterken, G.F., 1996. Natural woodland: ecology and conservation in northern temperate regions, Natural woodland: ecology and conservation in northern temperate regions. Cambridge University Press, Cambridge UK.

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