The cost of carbon retention by reduced impact logging

Reduced impact logging (RIL) is one means of reducing the carbon emissions held responsible for global warming. It may also reduce other adverse logging effects. A study of RIL effects was carried out in tropical rain forest in Sabah, Malaysia, as a joint venture between a major Sabah forest management company and a North American coal burning electrical utility. It sought to determine the extent to which RIL would reduce carbon dioxide emissions in comparison with conventional logging (CL). CL practice in Sabah is based on area control and managed through a system of annual coupes, controlled by diameter limit (all trees of >60 cm dbh -diameter at breast height - are felled); skidding is usually with bulldozers, about 40-70% of residual trees are damaged, and 117-30% of the logged area is traversed by bulldozers and left as open spaces. RIL prohibits logging in environmentally vulnerable areas, maps and plans the harvest area, skid trails and landings, carries out additional operations (such as tree marking, pre-felling vine cutting, and restoration of skid trails and landings), and undertakes all operations more carefully. Using RIL there was a 44% reduction of area logged within a tract, 22% reduction in timber yield per logged hectare, and 18% increase in cost per cubic metre logged compared with CL. Estimated timber yield at the next harvest was 31% higher following RIL. Compared with unlogged forest, RIL damaged rattans, wildlife, and soil and water quality values less than did CL. However, the environmental benefits of RIL per area of forest logged are considerably compromised by the greater logging area required for a given timber yield. Using RIL in place of CL had a net cost per unit area at all rates of discount. Per cubic metre of timber logged, RIL was beneficial without discounting, but had a net cost at a 2% discount rate and higher. The overall cost of the superior carbon retention in RIL varied with both discount rate and level of analysis, from a negative price to more than US$ 50 per metric tonne at a 10% discount rate. RIL appears most cost-effective on a per cubic metre logged basis at low discount rates. However, at commonly applied discount rates (4% and above) the carbon price of RIL exceeds most published estimates for carbon prices.