Optimal Sustainable Harvest Models for a Nigerian Tropical Rain Forest

A tree population growth matrix was used to investigate sustainable harvest models for a Nigerian tropical rain forest. Harvesting rates were simulated with cutting cycles of lengths ranging from 18–108 years under selective and non-selective loggings. In selective logging, a cutting cycle of 18 years with an exploitation rate of 30% produced 0·41 m2/ha, while a cutting cycle of 54 years using an 80% harvesting rate produced 1·10 m2/ha. The maximum sustainable harvest of 1·89 m2/ha was produced under a cutting cycle of 90 years with an exploitation rate of 100% of all merchantable trees. In non-selective logging, sustainable harvests increased with cutting cycles. A cutting cycle of 18 years produced 2·06 m2/ha with a 20% harvesting rate, while a cutting cycle of 54 years with a 40% exploitation rate produced 2·24 m2/ha. The maximum harvest of 5·47 m2/ha was produced under a cutting cycle of 108 years. The short cutting cycles of between 18 years and 72 years would only support fractional removal of merchantable trees, while the long cutting cycles of 90 years and over would support 100% removal of all merchantable trees. It was concluded that, currently, the rain forest was being over-exploited by as much as 20–50%.