Ecological effects of small-scale cutting of Philippine mangrove forests

Small-scale wood harvesting is one of the most ubiquitous forms of resource-use in the tropics, yet ecologists have barely studied it. This paper examines the effects of small-scale woodcutting on forest structure, composition and regeneration of mangrove forests in the Philippines. Information for the study was obtained through the application of extensive bio-ecological assessments of forests and interviews of forest users. Cut mangrove forests were characterized by smaller trees, less basal area and more canopy gaps. At least two-thirds of all canopy gaps were caused by cutting. In spite of these dramatic structural effects, there was little demographic evidence to suggest that significant changes to current species composition are occurring, although this may, in part, reflect that some species have already been eliminated from study areas by past cutting. Among common species, Rhizophora mucronata was the only one that appeared to be negatively impacted from cutting in terms of its relative abundance. Although abundance varied, seedlings of all common species measured were taller in canopy and/or expanded gap compared to understory, with Sonneratia spp. showing the greatest and Avicennia marina the least response. The particular success of A. marina in cut forests may be explained by the ability of its seedlings to better persist in the understory and thereby exploit gaps when these are created by cutting. Among common mangrove species, all but R. mucronata appear to be regenerating well in cut forests: Sonneratia sp., A. marina and R. apiculata regenerate well by coppice regrowth into the abundant small canopy gaps found in uncut and especially cut forests. Findings from this study highlight the significance of small-scale cutting disturbance and coppice regeneration as biotic factors in mangrove ecology.