2. Resources and Vegetation Systems

Forests and the major vegetation zones of the world

Climatic conditions in the world vary from cold (polar areas) to hot (tropical climates with heavy rainfall) to very dry and hot deserts (that are able to maintain only a minimal amount of plant life). Climatic factors (mainly temperature, precipitation or water availability) determine the distribution of the major forms of natural vegetation in the world. The world vegetation zones are called biomes meaning that major vegetation types extend over large areas in different parts of the world.

The significant diversity of forest resources or forest ecosystems is due their presence in a wide range of environments. This extends from the hot and humid tropics to the margins of the deserts and the arctic tundra communities. Within each vegetation zone there is a wide variety of local climatic, topographic and soil conditions. Certain tree species adapt to different ecological circumstances. Human influences can also impact the forest ecosystem, largely in the form of the introduction of exotic species and by the creation of forest plantations. This can often be very productive but is considered to be a simplified ecosystem.

In looking at the map of the biomes of the world (Figure F2) one can see almost half are characterized by forest vegetation. Many other biomes may also include some kind of forest cover or trees but they are not seen as the dominate natural vegetation. One should note that the names of biomes refer particularly to the dominant natural vegetation and land use (which may vary greatly). Thus, the role of forests in the landscape may be much smaller than originally thought. (i.e., due to past expansion of agriculture and deforestation). Biomes where forests thrive poorly or not at all for lack of sufficient temperature (polar ice, arctic tundra), nutrients (rocky areas) or water (deserts) are also hard places for human beings to live. Consequently, in those parts of the world where forests grow well, living conditions are also suitable for people and for industries. This means that forests have had to make room for agriculture, grazing, rural and urban settlements and other human activities (i.e., infrastructure).

Figure F2: The biomes of the world (FAO)

If we compare the map of world biomes at the European level (Figure F3) to the same area in the map of forest cover in Europe (Figure F5) we can see significant differences, and we have to remember that not all areas in Europe have forest cover or were forests in the past. 


Figure F3: Map of world biomes at European level (FAO)

Figure F5: Forest map of Europe (Schuck et al 2002) 1

Forest resources.  Besides ecosystems, forests are a valuable resource for people and society. In many cases, the terms forest, forest ecosystem and forest resource may mean almost the same thing, but the latter emphasizes more than just the ecosystem concept (i.e., the usefulness of forests for people). The term is also used when investigating the great number of forests and the changes that occur in them over the course of time. The concept of resource is also useful when classifying forests with regards to their availability for use by human. One may refer to available or economic forest resources, marginal forest resources and non-economic or non-commercial resources (these are without value either due to quality, small size or inaccessibility for some industrial or other forest use resource).

The measurement of the amount and characteristics of forests (forest resources) is called forest inventory or forest resource assessment. For this purpose a precise and clear definition of forest is important. In the most recent Global Forest Resource Assessment (FAO 2005), the term forest has been given the following definition: land spanning more than 0.5 hectares with trees higher than 5 meters and a canopy cover of more than 10 percent, or trees able to reach these thresholds in situ. It does not include land that is predominantly under agricultural or urban land use.2

Earlier two canopy cover criteria were used in world-wide forest resource assessments:  a 10% criteria was applied to forests located in"developing" countries and for "developed" countries it was 20%. The 10% percent criteria is now adopted everywhere.  

There are two other major land categories defined by FRA 2005:

1. "Other wooded land" means land not classified as a forest, spanning more than 0.5 hectares, with trees higher than 5 m and a canopy cover of 5-10 percent or trees that are able to reach these thresholds in situ; or with a combined cover of shrubs, bushes and trees above 10%. It does not include land that is predominantly under agricultural or urban land use.

2. "Other land" means all land that is not classified as a forest or other wooded land. It includes agricultural land, meadows and pastures, built-up areas and barren land.

However, areas classified under the subcategory 'other land with tree cover' also includes "other land with tree cover". This land is classified as other land (other than a forest or other wooded land), spanning more than 0.5 hectares with a canopy cover of more than 10% of trees being able to reach a height of 5 m at maturity. It includes groups and scattered trees in agricultural landscapes, parks, gardens and those surrounding buildings; provided that the area, height and canopy cover criteria are met. This includes tree plantations established mainly for purposes other than wood (such as fruit orchards).

When not regarded as forests or other wooded lands, the "trees outside forests" (TOF) (which may or may not meet all the criteria of other land with tree cover) provide many similar benefits as forest trees do and their contribution nowadays is being increasingly recognized.

Learn more about specific terms and concepts for forests - forest ecosystems and forest resources - are complementary to each other and provide reasons and possibilities to examine the special features of forests (FOR3), forest resources in global land use (FOR4), the quantitative characteristics of forest resources (FOR5) and the multitude of forest benefits (FOR6).  

FOOTNOTE 1: The names given to world biomes may differ in different contexts (i.e., the subtropical dry forest has also been called the Mediterranean forest, meaning it has roughly the same area).

FOOTNOTE 2: The definition includes bamboo, palm and other woody species.

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