The primary objective of the study reported in this thesis was to compare the ecological impacts of conventional (CNV) logging practices and reduced impact logging (RIL) techniques in Vanuatu. In Vanuatu, CNV logging techniques use ground-based machinery and are characterised by a fixed minimum diameter cutting limit, minimal environmental protection measures, poor logging planning, low levels of supervision and indiscriminate tree felling and machine use. By contrast, RIL techniques also use ground-based machinery but are characterised by appropriate logging planning, ecologically based silvicultural prescriptions, compliance with environmental protection guidelines and controlled machine use.
The methodology involved detailed data collection of the pre-logging and post-logging conditions on two similar sites of lowland tropical forest on north-east Efate, central Vanuatu. Systematic point sampling techniques, using optical prisms, on a grid pattern were used to determine pre-logging and post-logging stand compositions (stocking levels, diameter distribution, basal area and tree volume). In addition, visual post-logging assessments were made to determine the level of tree damage (in terms of causes, extent and severity) and the levels of soil and canopy disturbance.
Detailed analysis of the two logging systems showed that the poor planning, inadequate supervision, undisciplined machinery use and poor quality control measures associated with the CNV logging operation, degraded the residual forest, caused excessive soil disturbance, increased cutting cycle lengths and predisposed the regenerating forest to weed invasion.
Whereas CNV operations damaged 62% of all residual trees >1 cm dbhob in the post-logging stand, RIL techniques restricted damage to 19% of residual trees. Importantly from the perspective of the next harvest, CNV operations damaged 46% and 36% of all individuals in the post-logged stand >10cm dbhob and >40cm dbhob respectively; whereas RIL operations damaged 13% and 9% respectively. RIL techniques were shown to protect the advanced sapling and pole-sized individuals that would provide the stocking for subsequent harvests.
The RIL technique also reduced canopy disturbance from 67% down to 28%. The excessive gaps produced in the CNV operation benefited the non-commercial pioneer species to the detriment of commercial species and predisposed the forest to invasion by the climax community forming vine Merremia spp. RIL operations by contrast provided conditions for the regeneration of a balance of commercial and non-commercial tree species and for reduced vine invasion.
Importantly for the protection of forest soil and water values, compared to CNV logging, RIL techniques reduced soil disturbance from 22% to 9% of the ground surface area. Moreover, in the RIL post-logging stands, exposed soil on skid tracks incorporated leaf litter and were located away from watercourses and other sensitive areas of the forest, thus reducing the potential for off-site pollution.
In summary, the application of RIL techniques reduced ecological damage and therefore enhanced the potential for sustainable production forestry. Observations made during the studies suggest that RIL reduces the length of the cutting cycle and improves the economic returns of the logging operation.
Notwithstanding the clear benefits of RIL, CNV is universally used in the laissez-faire forest management systems commonly observed in developing countries. In addition to demonstrating the benefits of RIL for sustainable production forestry in Vanuatu, work reported in this thesis:
• highlights the individual elements of RIL;
• details the relative impacts of RIL practices and counterpart CNV practices;
• identifies silvicultural and logging support systems that would strengthen RIL in Vanuatu; and
• discusses the broader institutional, educational, commercial and market reforms needed to ensure uptake of RIL techniques in Vanuatu.