Natural Regeneration and Secondary Forests

Abstract

The easiest way of reforesting degraded lands is to take advantage of the capacity of many disturbed areas to recover unaided. The forests originating in this way are often referred to as secondary forests and these now cover large areas across the Asia-Pacific region. Many seemingly pristine forests are actually mosaics of undisturbed primary forest with patches of secondary forest of various ages arising from past shifting cultivation or natural disturbances. Indeed, some of these should be referred to as tertiary or quaternary forests because they have been disturbed on many occasions. It is difficult to make precise measures of the amount of secondary forest because of definitional problems (see below) and difficulties in mapping these forests using remote sensing technologies. However, de Jong et al. (2001) quote global estimates ranging from 340 to 600 million hectares and ITTO 2002) suggest secondary forests represent roughly 60% of the area now defined as tropical forests. In some countries the area of secondary forest far exceeds the area of undisturbed primary forest (Brown and Lugo 1990). In the Philippines, for example, secondary forests and brush-lands are thought to cover more than five million hectares while primary forests cover only 2.9 million hectares (Lasco et al. 2001).