The forestry industry in British Columbia (BC) is facing increasing scrutiny and shifting forest management objectives. Despite its operational efficiency, conventional clearcutting has received growing criticism for its adverse environmental impacts. Dispersed retention harvesting, a form of variable retention first proposed by American forester Jerry Franklin (1997), has been promoted as a more environmentally friendly and socially acceptable approach. Although early trials suggested that retention harvesting increases operational costs only modestly, it has gained little popularity. In this study, we tested dispersed retention harvesting in coastal BC at two retention levels (10% and 30%) using both a conventional whole-tree (WT) system and a less common cut-to-length (CTL) system. Productivity and costs were evaluated using automated machine data collection supplemented by a time study. Results from the cost analysis were then used in an economic analysis to compare the profitability of conventional clearcutting and dispersed retention systems. A residual stand damage assessment was also conducted to examine how damage occurrence varied by harvesting system and retention level. Lower productivity and higher costs were observed in the high-retention stands than in the low-retention stands. The CTL system was more cost-effective than the WT system in tree-to-truck operations; however, the economic analysis indicated a much lower net present value (NPV) for CTL because of lower log value and higher secondary transportation costs. Clearcutting consistently yielded the highest NPV, followed by a shelterwood system in which the initially retained trees are harvested after understory establishment. Retention systems produced the lowest economic returns, and profitability was negatively correlated with retention level. Uncertainty in stand development predictions remains a key limitation to robust economic analysis. Residual stand damage was significantly lower in blocks harvested using the CTL system than in those harvested using the WT system. However, only a small proportion of residual trees were severely damaged. Windthrow remains the primary driver of post-harvest stand structure change. We conclude that retention harvesting is operationally feasible in coastal BC, but it is less economically competitive than conventional clearcutting or the shelterwood system.
Shaojie Huang (Thu,) studied this question.