Impact of Forest Management on Species Richness: Global Meta-Analysis and Economic Trade-Offs

Abstract

Forests managed for timber have an important role to play in conserving global biodiversity. We evaluated the most common timber production systems worldwide in terms of their impact on local species richness by conducting a categorical meta-analysis. We reviewed 287 published studies containing 1008 comparisons of species richness in managed and unmanaged forests and derived management, taxon, and continent specific effect sizes. We show that in terms of local species richness loss, forest management types can be ranked, from best to worse, as follows: selection and retention systems, reduced impact logging, conventional selective logging, clear-cutting, agroforestry, timber plantations, fuelwood plantations. Next, we calculated the economic profitability in terms of the net present value of timber harvesting from 10 hypothetical wood-producing Forest Management Units (FMU) from around the globe. The ranking of management types is altered when the species loss per unit profit generated from the FMU is considered. This is due to differences in yield, timber species prices, rotation cycle length and production costs. We thus conclude that it would be erroneous to dismiss or prioritize timber production regimes, based solely on their ranking of alpha diversity impacts.

Figure 1. Changes in species richness of different taxonomic groups in response to ten most common forest management regimes.

Points represent mean response ratios and lines 95% confidence intervals. The top left panel shows responses for all taxa combined. The management regimes under which timber production is the main goal are showed in black, and non-timber regimes in blue. Horizontal red line signifies no change in species richness. An asterisk designates response ratios based on five or fewer comparisons. Numbers close to the x-axis are the numbers of comparisons. See also Supplementary Table S2 online.

Figure 2. Biodiversity-economic trade offs for ten hypothetical forest management units (FMU), described in the table at the bottom.

The top panel shows Net Present Value per hectare, assuming 75 years of management, and 10% discount rate. The central panel shows fraction of regional species lost when half of the original 10,000 ha of natural forest is subjected to forest management. The bottom panel shows the fraction of species lost per net profit, combining information from the two upper panels. See also Supplementary Table S5 online. *signifies FMUs for which production costs are specified in USD/ha, instead of USD/m³.