Do young eucalypt plantations benefit bats in an intensive agricultural landscape?

Abstract

Context Environmental benefits of timber plantations have been a major selling point for land use change from previously cleared farmland, but data concerning the response of biodiversity are scarce. Aims We investigated the use of young (4–11 years old) timber plantations by bats in comparison with other vegetation classes in a highly cleared and productive agricultural landscape in north-west New South Wales (NSW), Australia. Methods Initially, we recorded activity in paddocks before plantation establishment, and then four to six years after establishment. We compared activity within young eucalypt plantations with surrounding paddocks and remnant woodland. We also radio-tracked four different bat species to investigate how roosting and foraging was apportioned into different habitats. Key results The ultrasonic survey of bats found that the young plantations were typically used by 7–8 species and activity averaged 87 passes per night. Activity within plantations was similar to treeless paddocks, and approximately six times less than in small remnants. The very high activity levels and feeding buzzes in small remnants was significantly related to rich, basalt soil (which was used as a proxy for invertebrate biomass) on agricultural plains. Total activity and species richness was correlated positively with the number of remnant trees on the site, but neither plantation area nor shape influenced bat activity. Plantations were not used preferentially by radio-tracked bats at night compared with their availability in the local landscape (13–14% bat use, 17% available). No bat roosts were located within the plantations. Most bat roosts were in tree hollows, which were absent in the plantations. Decorticating bark was abundant in eucalypt plantations, but only Nyctophilus geoffroyi was observed beneath bark and only in remnant trees outside of plantations. Conclusions Young eucalypt plantations have limited value for bats, and this is comparable to previous studies on more environmentally focussed plantings. Implications The value of plantations for bats would be improved by retaining remnant trees, both in the surrounding landscape and within plantations. We also recommend varying tree densities to increase the diversity of animal species using plantations.