Action: Use selective or reduced impact logging instead of conventional logging
- Three studies evaluated the effects of using selective or reduced impact logging instead of conventional logging on bat populations. Two studies were in the Neotropics and one study was in Italy.
COMMUNITY RESPONSE (1 STUDY)
- Richness/diversity (1 study): One replicated, controlled, site comparison study in Trinidad found that the composition of bat species differed between selectively logged and conventionally logged forest.
POPULATION RESPONSE (2 STUDIES)
- Abundance (2 studies): A review of 41 studies in the Neotropics found that reduced impact logging had a significantly smaller effect on bat abundance than conventional logging. One replicated, site comparison study in Italy found greater bat activity (relative abundance) at two of three sites that used selective logging techniques to open up the forest canopy rather than leaving the canopy intact.
USAGE (0 STUDIES)
Selective logging is the removal of selected trees within a forest based on criteria such as diameter, height or species. Remaining trees are left in the stand, as opposed to clearcutting where all trees are felled.
Reduced impact logging is a sustainable harvesting and management method that aims to minimize ecological disturbance. It involves selective logging as well as other practices such as directional tree felling, stream buffer zones, constructing roads, trails and landings to minimum widths, and methods to extract timber with minimal damage. One study on reduced impact logging has been included but the effects of selective logging cannot be separated from the other interventions used.
Supporting evidence from individual studies
A replicated, controlled, site comparison study in 2001–2002 of six tropical forest sites in Victoria-Mayaro Forest Reserve, Trinidad (Clarke et al 2005) found that the composition of bat species differed between selectively logged forest, continuously logged forest and undisturbed forest. Significantly fewer fruit-eating and gleaning animal-eating bat species were captured in selectively logged forest (fruit-eating: 352 bats of nine species; animal-eating: 25 bats of seven species) than in continuously logged forest (fruit-eating: 958 bats of 13 species; animal-eating: 52 bats of eight species). In undisturbed forest, significantly fewer fruit-eating bats (282 bats of 10 species) and more animal-eating bats (71 bats of nine species) were captured than in either type of logged forest. In total, 38 bat species were captured (see original reference for data for individual species). Two sites were surveyed in each of three forest types: selectively logged forest (4–8 selected trees/ha felled in blocks of 150–300 ha), continuously logged forest (trees continuously felled creating an open canopy with fruit plants growing below) and undisturbed forest. At each of six sites, bats were captured at five sampling points using mist nets and harp traps for six hours from sunset on two nights in 2001–2002.
A review in 2014 of 41 logging studies in the Neotropics (Bicknell et al 2014) found that reduced impact logging had a smaller effect on bat abundance than conventional logging, even when conventional logging used similar harvesting intensities as reduced impact logging (≤30 m3/ha). The average effect sizes were significantly lower for reduced impact logging than for conventional logging (data reported as statistical model results). Effect sizes were calculated from a meta-analysis of all available studies (n = 41) and included multiple species-level comparisons for each logging method (reduced impact logging: 88 comparisons, all conventional logging: 139 comparisons; conventional logging with harvesting intensity ≤30 m3/ha; 84 comparisons). All 41 studies used selective logging alongside other interventions typical of reduced-impact logging such as directional felling, winching of logs and careful planning of logging roads.
A replicated, site comparison study in 2014 in three mixed forest sites across Italy (Cistrone et al 2015) found that ‘innovative’ selective logging resulted in greater bat activity than ‘traditional’ selective logging at two of three sites. Two sites had greater bat activity in ‘innovatively’ logged forest than ‘traditionally’ logged and unlogged forest (data reported as results of statistical models). One site had similar bat activity in ‘innovatively’ and ‘traditionally’ logged forest but significantly lower bat activity in unlogged forest (data reported as results of statistical models). Nine bat species were recorded in total (see original reference for data for individual species). In the ‘innovatively’ logged forest, trees were selectively retained (40–80 trees/ha) according to their shape, dominance, position and quality, and adjacent trees were cut to create openings. In the ‘traditionally’ logged forest, understorey trees were selectively thinned every 20–30 years and the canopy left intact. Unlogged forest had not been logged for >20 years. At each of three sites, three plots (3–6 ha) were surveyed for each of three treatments (‘innovatively’ logged, ‘traditionally’ logged, unlogged). Each plot was surveyed three times in June–September 2014 for two consecutive nights. Bat detectors recorded bat activity for eight hours from 30 minutes before sunset.
- Clarke F.M., Pio D.V. & Racey P.A. (2005) A comparison of logging systems and bat diversity in the Neotropics. Conservation Biology, 19, 1194-1204
- Bicknell J.E., Struebig M.J., Edwards D.P. & Davies Z.G. (2014) Improved timber harvest techniques maintain biodiversity in tropical forests. Conservation Biology, 19, R1119-R1120
- Cistrone L., Altea T., Matteucci G., Posillico M., De Cinti B. & Russo D. (2015) The effect of thinning on bat activity in Italian high forests: the LIFE+ "ManFor C.BD." experience. Hystrix, the Italian Journal of Mammalogy, 26, 125-131