Forest cover

Forest cover: an indicator of deforestation

The planet’s forests have long been the victims of clearing to make way for agriculture or grazing land. They host considerable biodiversity which is threatened by their disappearance. Tropical forests now cover only 7% of land, yet are home to over half of the world’s living species.

Forest replanting endeavours partly offset deforestation, especially in Asia, however most of these are monocultures, often of exotic species, and host low biodiversity. Deforestation also contributes to greenhouse gas emissions, and thus worsens the greenhouse effect.

The forest cover indicator is the ratio of wooded land area to a country’s total land area. However, there is ambiguity surrounding the term “wooded”, which can be somewhat arbitrary. Depending on the definition used, wooded land on a global level can be assessed at anywhere between 2.4 and 6 billion ha. The benchmark definition is established by the FAO (see above).

At the turn of the millennium, the average world forest cover accounted for 30% of surface area, with higher percentages in South America (50%), Europe, and Russia (46%). Other continents had significantly lower percentages of forest cover: North and Central America (26%), Oceania (23%), Africa (22%), and Asia (18%). Africa, however, is a continent of many contrasts, with large stretches of desert existing alongside lush forest regions (Gabon, Democratic Republic of the Congo).

Deforestation was particularly severe during the last decades of the 20th century, but appears to be slowing slightly since the turn of the millennium. Overall, deforestation is decreasing by 0.2% per year; the rate is greatest in Africa, at 0.8% per year. This decrease may be related to environmental lobbying; however it is most likely owing to the fact that the easiest and most profitable forestry areas have already been harvested.

The forest cover is increasing in some countries, especially in France, due the rural exodus of that country.

Definition of the indicator

The term “forest” is difficult to define. There are no simple criteria to do so, resulting in many different definitions. The FAO definition is based on three main criteria: the area in question must measure a minimum of 0.5 ha, present tree crown cover of at least 10% (to distinguish true forests from areas with trees), and trees must reach a minimum height of 5 m at maturity (to distinguish trees from shrubs).

The advantage of this definition is that it provides a common basis by which to measure forests. However, there are notable exceptions, such as the Russian Taiga, made up of dwarf pine and spruce that measure less than 5 m. Depending on which definition is used, this forest may or may not be counted in the world total, resulting in an astonishing 20% difference in final figures. Similarly, if the area under examination must be at least 20% wooded, as is often the standard in Europe, several forest areas would not be taken into account, such as those already damaged through incipient deforestation.