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The effectiveness of the multi-spatial scale approach to forest management: A case study of Tasmanian bats

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posted on 2023-05-27, 01:12 authored by Cawthen, L
Sustainable forest management is increasingly being recognised as a key component of biodiversity conservation, as much of the world's terrestrial biodiversity is dependent on forests. Understanding the effectiveness of approaches to forest management and how they are implemented in on-ground in practice is crucial for the ongoing improvement of forest management strategies for biodiversity conservation. This is especially so in Tasmania's dry Eucalypt forests where a range of land management practices, such as timber harvesting, have altered the type, amount and spatial arrangement of mature forest available to fauna. Using Tasmania's hollow-roosting bats as a case study, the overall aim of this thesis is to gather information that can be used to assess the effectiveness of a multi-spatial scale approach to forest management, as applied on the ground in Tasmania. In particular this thesis aims to determine how effectively retained forest habitat provides suitable habitat for hollow-using bats, facilitates recolonisation of harvested areas and thus maintains bat populations in timber production landscapes. Effectiveness monitoring for biodiversity conservation can be hampered by a lack of basic information on the species studied, as was the case in Tasmania. In order to understand the effectiveness of forest management strategies I first had to develop an accurate method for identifying bat calls recorded during bat call surveys. Bat call surveys were used to assess the spatial and temporal variation in bat activity, species richness and assemblages across and between landscapes. I then had to establish baseline data on the basic life history and activity patterns of Tasmanian bats to understand how temporal variation in bat activity is related to changes in the timing and patterns of reproduction. The findings of these studies fill a significant gap in our understanding of Tasmania's bats. Notably, the discovery of the whitestriped freetail bat in Tasmania during these studies highlights the importance of collecting such data and monitoring bat communities. Importantly the information derived from these studies provided the necessary information for using radio-telemetry and bat call surveys to investigate the effectiveness of forest management strategies for bats. The main findings of this thesis were that no single forest retention measure was preferred by all bats or catered for all their habitat requirements (e.g. food, shelter and breeding sites).This is because species and individuals varied in their habitat requirements. Such differences are likely underpinned by variations in their social, physiological and ecological needs. The effectiveness of different forest retention measures for bats also varied between landscapes. In landscapes where mature forest was rare or lost, small patches (<1ha) and large strips (50ha) were used more extensively by bats than in landscapes where mature forest was more abundant. Not all species formed maternal colonies in such patches and strips, instead preferring large patches (>350ha) to breed. All species, however, did show a preference for roost areas, though not always roost sites, in parts of the landscape with the highest availability of hollow-bearing trees. The findings of this thesis indicate that Tasmania's current forest management strategies are effective at providing suitable habitat for bats, facilitating recolonisation of harvested areas and maintaining bat species in the landscape. They also support the multi-spatial scale approach to forest management as applied on the ground in Tasmania as a viable and effective way of conserving bats in Tasmania's timber production forests. A 'one-size-fits-all approach' is unlikely to cater for the habitat requirements of all bats. These findings have important implications for the continued improvement of forest management strategies in humanmodified landscapes and demonstrate that native forest management can be an important part of any biodiversity conservation strategy, provided that habitat is retained into the future at a variety of spatial scales and taking into consideration the broader landscape.

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