Winners and losers among mammals and nocturnal birds over 17 years in response to large-scale eucalypt plantation establishment on farmland

Abstract Large-scale plantations established for timber production can dramatically transform landscapes, however little is known about the response of more cryptic components of biodiversity. We report on trends in mammals and nocturnal birds during a 17 year longitudinal study on three large-scale plantations of locally indigenous eucalypts in northern New South Wales, Australia. The study began in a farmland mosaic and has continued to track occupancy after the establishment of eucalypt plantations within the paddock areas. Surveys were undertaken at focal trees located in different classes of remnant vegetation that became embedded within the plantations as well as in the plantation matrix itself. Reference sites were also sampled in adjacent blocks of forest. We recorded nine species of arboreal mammals and eight species of nocturnal birds during focal tree watches, while camera and Elliott traps recorded 19 ground-dwelling taxa. Eleven of these species are listed as threatened. The majority of species were present, but uncommon, at the start of our study in the cleared farmland-remnant vegetation mosaic. Multi-season, multi-scale occupancy analyses revealed most species were stable over time and, among mammals, a large temporal increase was most notable for common brushtail possum Trichosurus vulpecula . A potential decline was only observed for eastern chestnut mouse Pseudomys gracilicaudatus , a trend also evident in other small mammals. Among nocturnal birds, both southern boobook Ninox boobook and Australian owlet nightjar Aegotheles cristatus increased in occupancy over time. Increasers tended to be widespread species with generalist attributes, while stable or decreasing species were more likely to be specialists. Few arboreal mammals or nocturnal birds were recorded in the plantation matrix itself, though some ground mammals (e.g., rufous bettong Aepyprymnus rufescens ) had higher occupancy rates in plantation. Rather, most species were associated with remnant vegetation and old growth elements within plantations and these likely function as a refuge for fauna (potentially during plantation harvest), provide specialised resources such as tree hollows and facilitate the colonisation of plantations. While few negative effects due to change in land-use to plantation were recorded, limited increase in occupancy for most species contrasts with overall positive trends reported previously for diurnal bird species. Low structural complexity and tree species diversity within plantations are likely to limit the number of winners. In the context of a timber plantation, additional management to enhance recovery would best be directed to areas excluded from future harvesting, such as environmental plantings in degraded riparian zones and limiting livestock grazing. The ecosystem implications of increasing populations of generalists such as T. vulpecula remain unclear.