Report 2 Stage II July 2000 IMPACTS OF ROADS & POWERLINES ON THE WET TROPICS OF QUEENSLAND WORLD HERITAGE AREA Miriam Goosem Steve Turton Wet Tropics Management Authority and Rainforest CRC James Cook University, Cairns Campus IMPACTS OF ROADS AND POWERLINES Terms of Reference Roads and Power Lines Project To examine the impacts of roads and powerlines on the fauna and flora of the Wet Tropics and to determine the effects of road closure and restricted use on native fauna and flora. Through the Wet Tropics Plan a number of roads and tracks have been closed or have restricted access because of their potential impact on fauna and flora. This project will monitor the impacts of road/track closure/opening on the native fauna and flora and the spread of exotic weeds and other pest organisms. It will look at the damage to roads/tracks caused by increased use. In summary this project will provide: 1) An assessment of the impact of road/track closure/opening on the Wet Tropics 2) An assessment of road/track damage through increased or decreased use 3) Indicators of impacts of road opening/closure for future monitoring. Outcomes for WTMA: • Increased knowledge base for decision-making on roads and tracks in the Wet Tropics • Improved decision-making for permits and road management and usage (Ref: Contract No. 420) Acronyms DNR Department of Natural Resources EPA Environmental Protection Agency (formerly the Department of Environment and Heritage) GIS Geographic Information System Rainforest CRC Cooperative Research Centre for Tropical Rainforest Ecology & Management TESAG School of Tropical Environmental Studies and Geography, James Cook University QPWS Queensland Parks and Wildlife Service (formerly the Department of Environment and Heritage) WTMA Wet Tropics Management Authority WTQWHA Wet Tropics of Queensland World Heritage Area WTMP Wet Tropics Management Plan i IMPACTS OF ROADS AND POWERLINES Acknowledgments Many people have made contributions to the roads and powerlines project: We would especially like to thank the Wet Tropics Management Authority and Rainforest CRC for their financial contributions. Special thanks also for the additional funding received from the Department of Natural Resources and the Environmental Protection Agency and Queensland Parks and Wildlife Service. The Wet Tropics Management Authority, Environmental Protection Agency and the Department of Natural Resources all supplied in kind support. We are especially grateful to Dr Steve Goosem and Mr Terry Webb of the Wet Tropics Management Authority, who provided significant input to this project. Additionally, Wet Tropics Management Authority personnel provided: (1) GIS support - access to spatial databases and professional advice; (2) Access to library facilities, reports and data sets; (3) Loan of traffic counters; and (4) Project consultation and professional advice from both scientific and planning staff. In kind support from the Department of Natural Resources and the Environmental Protection Agency and the Queensland Parks and Wildlife Service was in the form of: (1) Professional advice from management, research, permit and on-site staff; (2) Information with respect to DNR counters; and (3) Access to library facilities, reports and data sets. The School of Tropical Environment Studies and Geography and the Rainforest CRC, James Cook University, Cairns Campus, provided infrastructure, both academic and technical advice, and equipment and administrative assistance where required. We would also like to thank Sharon Marks, Bachelor of Applied Science Honours student (TESAG), Susan Siegenthaler, Bachelor of Science Honours student (TESAG), Glenys Diprose, Bachelor of Science Honours student (Earth Sciences) and Nigel Weston, Master of Applied Science student (TESAG) for their contributions and hard work. We acknowledge the contributions and extend our thanks to our research assistants Tara Day, Sharon Marks and Susan Siegenthaler. Tara Day has been responsible for much of the final editing and compilation of this report. Many people from research, tourism and management backgrounds generously contributed their professional knowledge to the collation of data for the arboreal road crossing questionnaire. Their contributions are gratefully acknowledged. Dr Miriam Goosem (Post-Doctoral Research Fellow, Principal Researcher) Dr Steve Turton (Associate Professor of Geography, Principal Researcher) ii IMPACTS OF ROADS AND POWERLINES Contents Page Terms of Reference i Acronyms i Acknowledgments ii Executive Summary v Section 1: The Effect of Canopy Closure and Road Verge Habitat on Small Mammal Community Composition and Movements 1 Summary 2 1.1 Introduction 2 1.2 Methods 4 1.3 Results 6 1.4 Discussion 15 1.5 Conclusions 18 1.6 Management Implications 18 1.7 Future Research 18 Section 2: Edge Effects of Roads and Powerline Clearings on Microclimate 19 Summary 20 2.1 Introduction 20 2.2 Methods 22 2.3 Results 27 2.4 Discussion 41 2.5 Conclusions 42 2.6 Management Implications 43 Section 3: Edge Effects of Roads and Powerline Clearings on Rainforest Vegetation 45 Summary 46 3.1 Introduction 46 3.2 Methods 48 3.3 Results 50 3.4 Discussion 61 3.5 Conclusions 63 3.6 Management Implications 63 iii IMPACTS OF ROADS AND POWERLINES Section 4: Geochemical Impacts on Roadside Soils in the Wet Tropics of Queensland World Heritage Area as a Result of Transport Activities 65 Summary 66 4.1 Introduction 66 4.2 Methods 68 4.3 Results 72 4.4 Discussion 79 4.5 Conclusions 80 4.6 Recommendations 81 4.7 Management Implications 81 4.8 Future Research 81 Section 5: Vehicular Noise Disturbance in Rainforest 83 Summary 84 5.1 Introduction 84 5.2 Materials and Methods 85 5.3 Results 88 5.4 Discussion 92 5.5 Conclusions 93 5.6 Recommendations 94 Section 6: Evaluation of Overpasses as Crossing Routes for Arboreal Species 95 Summary 96 6.1 Introduction 96 6.2 Methods 98 6.3 Preliminary Results 101 6.4 Discussion 103 6.5 Management Implications 104 Section 7: Road Crossings by Arboreal Mammal Species Questionnaire 105 Summary 106 7.1 Introduction 106 7.2 Methodology 107 7.3 Results 108 7.4 Discussion 110 7.5 Conclusions 116 7.6 Recommendations 116 7.7 Management Implications 117 References 119 Appendices Section 2 Appendix: Edge Effects of Roads and Powerline Clearings on Rainforest Microclimate A2-1 Section 3 Appendix: Edge Effects of Roads and Powerline Clearings on Rainforest Vegetation A3-1 Section 4 Appendix: Geochemical Impacts on Roadside Soils in the Wet Tropics of Queensland World Heritage Area as a Result of Transport Activities A4-1 Section 7 Appendix: Species Habitat and Distribution and Road Crossing Summaries A7-1 iv IMPACTS OF ROADS AND POWERLINES Executive Summary Section 1: The Effect of Canopy Closure and Road Verge Habitat on Small Mammal Community Composition and Movements Research Objective The objective of this study was to examine the effects of narrow rainforest roads on small mammal community composition and movements with the following aims: • To determine whether edge effects in small mammal community composition differ between areas where there are no roads (forest interior), along narrow roads where rainforest canopy closure is maintained and along narrow roads with wide grassy and woody weed verges; • To determine to what degree small mammal movements are inhibited by a narrow rainforest road with canopy closure or with a wide grassy and woody weed verge; and • To determine whether small mammal species alien to the rainforest habitat are able to penetrate areas where there are no roads (forest interior), where rainforest canopy closure is maintained or where a wide grassy and woody weed verge is present. Key Findings • Grassland and feral small mammals can intrude along the grassy and woody weed verges of a narrow road traversing rainforest. These species existed even where short lengths of road with canopy closure subdivided the grassy verge habitat. However they failed to penetrate the rainforest interior and were not resident at the road edge where canopy closure was maintained. • Rainforest small mammals were not excluded from a narrow grassy and woody weed verge either by the alien habitat or by the presence of grassland small mammals, possibly due to the proximity of woody weeds which appeared to be favourable, though not ideal, habitat for rainforest species. However rainforest species abundance was halved in comparison to that of the adjacent forest edge and interior. • Small mammal community composition at the edge was altered adjacent to a narrow road with a grassy verge, with generalist species increasing and a concomitant reduction in a more specialist rainforest species. However, where canopy closure was maintained and there was little obvious disturbance to the understorey and ground layers, small mammal communities were comparable to the forest interior with the exception of a probable reduction in abundances of less common species. • The narrow road caused inhibition of crossing movements of several small mammal species, regardless of the clearing type (grassy and woody weed verge or closed canopy) in comparison with the forest interior. Movements of a larger species were unaffected by a road with canopy closure. Recommendations • Maintenance of canopy closure to prevent intrusions into rainforest of small mammals alien to rainforest habitats and reduce edge effects in small mammal community composition. Management Implications • A grassy and woody weed verge allows penetration of small mammals alien to the rainforest environment, but these species do not penetrate the forest interior or where canopy closure is maintained over the road. • Canopy closure also reduces edge changes in small mammal community composition in comparison to rainforest edges adjacent to grassy and woody weed verges. • The presence of the road is the primary factor causing inhibition of road crossing movements by rainforest small mammals, irrespective of whether the clearing has canopy closure or grassy and woody weed verges. Further Research • It is hoped to continue this study in the vicinity of the Maalan Road, to examine the success rate of rehabilitation strategies and the effects of weed control undertaken by management agencies.