Retain existing in-field trees
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
Single or scattered trees, particularly mature or veteran trees, may provide important roosting and foraging habitat for bats in open agricultural landscapes. Existing trees in both arable and grassland fields should be retained and protected. This may include avoiding use of pesticides, fencing off trees to prevent damage by livestock, and leaving an uncultivated buffer around each tree. For studies that may carry out this intervention alongside other interventions to benefit bats on farmland, see ‘Introduce agri-environment schemes’. For studies that relate to retaining remnant forest or woodland, see ‘Retain remnant forest or woodland on agricultural land’.
Supporting evidence from individual studies
A replicated study in 2002 of 24 agricultural sites in southeastern Australia (Lumsden & Bennett 2005) found that paddocks with scattered trees had higher activity for four bat species than paddocks without trees, but no difference was found for six other bat species/species groups. Average bat activity was significantly higher in paddocks with high, moderate and low densities of scattered trees than treeless paddocks for Gould’s wattled bat Chalinolobus gouldii (scattered trees: 6–7 bat passes; treeless paddocks: 1 bat pass), chocolate wattled bat Chalinolobus morio (scattered trees: 2–4 bat passes; treeless paddocks: 0.3 bat passes), and little forest bat Vespadelus vulturnus (scattered trees: 14–36 bat passes; treeless paddocks: 2 bat passes). For the western broad-nosed bat Scotorepens balstoni, the difference was only significant between paddocks with a high density of scattered trees (average 1 bat pass) and treeless paddocks (average 0.1 bat passes). There was no significant difference between paddocks with scattered trees and treeless paddocks for the activity of six other bat species or species groups (see the original reference for detailed results for each species). Two sites were sampled in three different study areas for treeless paddocks and for each of three densities of scattered trees (high: 10–34 trees/ha; moderate: 1–9 trees/ha; low: <1 tree/ha). Each of 24 sites was sampled with a bat detector for four nights in January–April 2002.Study and other actions tested
A replicated, site comparison study in 2007–2008 at 63 agricultural sites in New South Wales, Australia (Fischer et al 2010) found that grazed pasture with scattered trees had higher bat activity and more bat species than grazed pasture without trees. Overall bat activity was higher at sites with 1–2 trees (average 40 bat passes/night), 3–5 trees (average 330 bat passes/night) and >6 trees (average 95–380 bat passes/night) than at treeless sites (average 2 bat passes/night). More bat species were recorded at sites with 1–2 trees (5 species), 3–5 trees (7 species) and >6 trees (6–8 species) than at treeless sites (2 species). All of 63 sites (2 ha) were in grazed pasture with no trees or scattered trees (either 1–2, 3–5 or >6 trees/site). The number of sites for each treatment are not reported. Each of 63 sites was surveyed with two bat detectors on four nights in November–December 2007/2008 and in February–March 2008.Study and other actions tested