Chronic disturbance, a principal cause of environmental degradation in developing countries

Impact of human action is being felt in all ecosystems. Traditionally, urban landscapes and agricultural fields have been considered to be dominated by humans, but human alteration has also been substantial in tropical forests. The common forms of acute forest disturbance are ones that involve logging selectively or clear-cutting, allowing forest to regenerate by natural means. In contrast to the acute forms of disturbance, the chronic form of disturbance, which is subtle and slowly creeping, but equally destructive, is a much less-recognized problem. In the chronic form of disturbance people remove only a small fraction of forest biomass at a given time, generally as head-loads of firewood, or in the form of fodder, leaf litter and other non-timber forest products (NTFPs). The problem with the chronic form of forest disturbance is that plants or ecosystems often do not get time to recover adequately, because the human onslaught never stops, and can cause adverse changes in the forest, even if rates of biomass removal are within the carrying capacity of the forest. In a similar fashion, the cumulative effects of low but chronic exposure to air pollution are now cause for concern all over the planet (Pitelka 1994). In the case of chronic forest disturbance, the effect somewhat resembles that of persistent insect herbivory at a moderate scale. Fuelwood, which is still the main source of cooking energy in most developing countries, is reported to be in under supply for 1.4 thousand million people, and these may rise to 2.5 thousand million by 2010 (Food and Agriculture Organization 1994). Therefore, more areas are likely to come under regimes of chronic disturbance in the next century.