Author: AE van Wyk ~ Department of Botany,University of Pretoria
( Article Type: Explanation )
Afforestation refers to the establishment of commercial tree crops by purposeful planting on land previously not used for tree crops, e.g. the establishment of monocultures of pines, eucalypts or wattles in areas of primary grassland in South Africa. The resultant tree stand usually consists of a single species (monoculture), referred to as a plantation. In contrast, reforestation is the replanting of trees on previously forested land. In practice, however, the terms afforestation and reforestation are often used interchangeably, resulting in considerable confusion as to the precise nature of a tree-planting activity. This is particularly the case in areas where natural forest is being harvested commercially, as in many temperate parts of the northern hemisphere, followed by selective replanting with one or a few (but not all) of the species originally present in the forest.
The impoverished tree stand thus established through so-called reforestation approaches a plantation rather than a true natural forest. Reforestation also refers to the establishment of a new commercial tree crop on land from which a planted tree crop had been harvested, regardless of the type of natural vegetation that originally existed in the area. Because of the widespread misuse of these terms to hide environmentally destructive activities, it is essential to establish whether the particular tree planting activity is for commercial purposes (establishment of a plantation) or the restoration of a natural forest for non-commercial purposes following damage or degradation (rather rarely attempted because of its non-commercial nature). Deforestation, on the other hand, is the destructive process of clearing a natural forest.
Commercial afforestation rather than deforestation is a cause of major environmental degradation and social problems in many parts of the world. Effects of large-scale monoculture tree plantations, especially on grassland biodiversity, can be disastrous. Negative impacts are aggravated by the uncontrolled spread of alien trees beyond the plantation, by bush encroachment due to inappropriate management of grassland enclaves within plantation areas and by changes in the local hydrology. Although tree plantations are often promoted as environmentally friendly under the pretence that they are ‘forests’, in many parts of the world these plantings are seen as green wastelands from a biodiversity point of view. A clear distinction should therefore be made between the concepts ‘forest’ and ‘plantation’. Forests are complex, self-regenerating natural ecosystems rich in biodiversity; plantations are artificial plantings of a tree crop.
South Africa already has more than 1.5 million hectares of alien tree plantations, mostly composed of eucalypts, pines and wattles. Timber companies are, however, increasingly acknowledging the negative effects of afforestation and are attempting to lessen the negative impact by setting aside land (still negligible, it must be said) for conservation purposes.