Fragmentation is a severe threat to tropical rainforests.
However the habitat loss and less extensive fragmentation
caused by roads can also be a threat, not only through allowing access to remote areas, but also through a suite of insidious associated impacts. These include abiotic and biotic edge effects adjacent to road clearings, the disturbance impacts caused by vehicle operation, invasions by weeds, feral and alien fauna and disease, and faunal mortality from vehicle collisions. In combination, these can create a significant barrier to movements of rainforest biota. Impacts can be ameliorated through clever road design and sustainable vehicle operation.

Fragmentation impacts caused by roads through rainforests

We investigated the use of inexpensive aerial bridges (rope canopy bridges) above roads and a highway by arboreal mammals in the Wet Tropics of Queensland, Australia Three rope bridge designs were trialed, including a single rope, ladder-like bridges and tunnel-shaped bridges Nine mammal species were recorded using canopy bridges, including five species or subspecies endemic to the Wet Tropics and three species listed as rare under State nature conservation legislation Most of these species suffer severely from either the fragmentation or mortality impacts caused by roads Over 50 crossings above a 15-m-wide tourist road were observed on an elevated ladder-like bridge Longer (~40 m) rope bridges were used on several occasions by four species Our observations suggest that canopy bridges can assist rare arboreal mammals to cross roads in the Wet Tropics, thereby reducing both the risk of road-kill and the potential for subpopulation isolation Further research is required to ascertain the level of benefit afforded by canopy bridges for arboreal mammal populations It is likely that rope canopy bridges will have broad application for a range of arboreal mammal species

Using canopy bridges to link habitat for arboreal mammals: successful trials in the Wet Tropics of Queensland

Within the expanding city of Brisbane in south-east Queensland, numerous fragments of native and regrowth vegetation are scattered across the largely urbanised landscape. These fragments provide refuge to a great diversity of native wildlife, and, provide residents with the opportunity to experience nature on their doorstep. To assess the diversity and abundance of this wildlife, recent changes in these parameters, and the value of wildlife and bushland fragments to residents of Brisbane, a questionnaire survey was distributed to 300 households each located adjacent to one of 38 urban bushland fragments. A total of 172 surveys (57%) were returned, producing 768 records of 83 fauna species, dominated by birds and mammals; bandicoots were widely reported from the 38 fragments. Several historical records provided evidence of recent local extinctions within fragments, highlighting the continuing declines in various species of native wildlife within Brisbane. Several human-wildlife conflicts were identified, but overall residents were tolerant of such conflicts. Bandicoots were disliked by a small minority (3%) of residents owing to the holes they dig in lawns and gardens in search of food. and their potential as vectors of ticks. Most respondents expressed ail appreciation for the presence of native wildlife (96%) and bushland fragments (97%) in their local area, emphasising the importance of incorporating human dimension values into the management of this urban biodiversity.

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A community-based wildlife survey: the knowledge and attitudes of residents of suburban Brisbane, with a focus on bandicoots

are published by the School of Economics, University of Queensland, 4072, Australia, as follow up to the Australian Centre for International Agricultural Research Project 40 of which Professor Clem Tisdell was the Project Leader. Views expressed in these working papers are those of their authors and not necessarily of any of the organisations associated with the Project. They should not be reproduced in whole or in part without the written permission of the Project Leader. It is planned to publish contributions to this series over the next few years. Research for ACIAR project 40,

Economics, ecology and the environment

The effects of roads on wildlife behaviour and ecological function are poorly known in arid Australia. The most obvious impact is roadkill from wildlife-vehicle collisions. Therefore we collected statistics on kangaroo-vehicle collisions, investigated the causal factors of these collisions, and related roadkill mortality to the population structure, size and distribution of four kangaroo species in two intensive six month studies during and following drought. The research was conducted along a 21.2 km sealed section of the Silver City Highway between Broken Hill and Tibooburra that passes through the University of New South Wales (NSW) Arid Zone Research Station at ‘Fowlers Gap’ in north-western NSW. The rate of roadkill was higher during drought (20.8 roadkills month-1) than non-drought (2.6 roadkills month-1). Affected species were red kangaroos (Macropus rufus), euros (Macropus robustus erubescens), western grey kangaroos (Macropus fuliginosus) and eastern grey kangaroos (Macropus giganteus). During drought, M. fuliginosus and M. giganteus were killed in lower proportions than their proportion in the source population, otherwise species were killed in proportion to their density along the road. There were no sex biases but male M. r. erubescens were much more likely to be beside the road than females and thus were killed more often during drought. The majority of roadkills were young individuals around 2 years old. Curves and stockraces along the road significantly increased the likelihood of roadkills. Likewise the frequency of roadkills was a function of the kangaroo population density along the road, night time traffic volume, low rainfall and higher vegetation cover and greenness along the road relative to surrounding areas. We evaluate the relationships between these causal factors and kangaroovehicle collisions, and discuss the possible effects of these collisions on kangaroo population structure under drought and post-drought conditions.

Kangaroo-vehicle collisions in Australia's sheep rangelands, during and following drought periods.

Lumholtz's Tree-kangaroo Dendrofagus lumholtzi is endemic to the rainforests of north Queensland, Australia. Most records of D. lumholtzi are from upland forests on the Atherton Tablelands, an area -extensively cleared for agriculture. In 1997, residents of the Tablelands formed the Tree Kangaroo and Mammal Group Inc. (TKMG) with the aim of promoting the conservation of the species. The first project of TKMG was an intensive community-based survey of the
distribution of D. fumholtzi. Residents of all postal districts encompassing areas of upland rainforest within the range of D. lumholtzi were sent a written questionnaire seeking details of tree-kangaroo sightings. The Malanda postal district was surveyed in 1998 while all other postal districts were surveyed in 1999. In total, 10 122 questionnaires were distributed in the survey. Nearly BOO responses were received to the survey, providing 2 36B Sighting records of D. lumholtzi. Of these, 367 records were of dead tree-kangaroos, mostly road-kills." The survey has provided a much more comprehensive account of the distribution of the species than was previously available. Most records of D. lumholtz; obtained in the survey were from upland forests between Atherton and Ravenshoe, particularly remnant forests in the central and western Tablelands. Although the survey methodology is biased towards areas frequented by humans, these patterns are consistent with independent surveys. The conservation of D. lumholtzi on the Tablelands would benefit from the protection of remnant forests, the restoration of habitat and a reduction in the incidence of road-kills and dog attacks on tree-kangaroos.

B. Stirn

Papers

Community survey of the distribution of Lumholtz's Tree-kangaroo on the Atherton Tablelands, north-east Queensland