Sustainability of reduced-impact logging in the Eastern Amazon

Abstract

Damage caused by reduced-impact logging (RIL) was assessed in 18 plots 1 ha each in a terra firme rain forest of Eastern Amazon (Brazil, Paragominas). Mean logging intensity was 6 trees ha −1 and the resulting commercial volume 21 m 3 ha −1. On average, logging damage affected 16% of the original stand while skidtrails occupied 7% (661 m 2 ha −1) of forest soil area. Canopy openness doubled to a mean of 11%. Of the variables studied, “number of trees harvested or felled per plot” gave the best correlation to “proportion of damaged or destroyed trees”. Damage to each diameter class was distributed in accordance with relative abundance of trees (dbh ≥ 20 cm) in the original population before logging, suggesting that all diameter classes were affected equally. The sustainability of timber management applying RIL was evaluated through the calculation of the recovery level of commercial trees in three different scenarios. In the most optimistic scenario (growth rate of 5 mm year −1 and 1% annual mortality), after 30 years, only 50% of the commercial stand would recover, provoking a drastic reduction of the harvesting intensity at the second felling cycle. Within a 30-year felling cycle (i.e. the legal felling cycle duration in the Brazilian Amazon) and even under RIL systems, the present logging intensity occurring in the study area (6 trees ha −1) is not compatible with sustainable yield production on a long-term basis. For the study area, only the implementation of silvicultural treatment ensuring that the remaining potential crop trees grow at 4–5 mm year −1 would guarantee a logging intensity of 3–4 trees ha −1 (10–14 m 3 ha −1) 40 years after the first harvest. This study showed that in the Amazon, RIL alone is clearly not sufficient to achieve sustainable forest management. More sophisticated silvicultural systems must be urgently elaborated and implemented to ensure that the forest will still be sustainably managed on a long-term basis. This issue is particularly important in the case of Brazil as a new law allowing the creation of 500,000 km 2 of forest concessions by 2010 has been recently approved by the congress.