Background. At least a fifth of tropical forests have been logged in the recent past. This practice is an important source of timber but there are concerns about its long-sustainability and impacts on biodiversity and carbon storage. However, there is wide variation in the impacts of logging, making generalisation, and thus policy implementation, difficult. Recent syntheses of animal biodiversity have indicated that differences in logging intensity – the volume of wood removed per hectare – may help explain some of these differences. In addition there have been suggestions that reduced impact logging (RIL) may reduce some of the negative effects of logging.
Methods. We aimed to test these hypotheses using meta-analyses to explore differences in the impacts of logging on (1) residual tree damage, (2) aboveground biomass and (3) tree species richness. To do this we used a mixture of unweighted mixed models and weighted meta-regression
Results. Our results indicate that RIL may reduce residual tree damage when compared to conventional methods, but that at higher logging intensities this effect is negated. Changes in aboveground biomass were negatively related to logging intensity, but any effect of RIL was obscured by it being carried out at relatively low intensities. Tree richness appeared to initially increase at low intensities but was reduced at higher intensities.
Discussion. Our results give only weak support to the hypothesis that RIL reduces the negative impacts of logging on tree damage, and do not support suggestions that RIL reduces loss of biomass or species richness. However, we do not think this is because there is no difference between the impacts of RIL and conventional logging but rather that better evidence is needed to assess these differences. We suggest that studies that take account of plot-level differences in logging intensity are likely to provide a solution to this knowledge gap.