Wetlands, Biodiversity and Salt

Frogs August 2006

Overview We described changes in frog diversity in non- Non-riverine wetlands are particularly riverine wetlands along a salinity gradient in important habitat for local and regional the Wimmera region – an area that is biodiversity. The successful management of threatened by secondary salinisation. This these ecosystems relies on understanding information was collected to allow us to better changes in wetland function and biodiversity in understand the threat that increasing salinity response to a range of threatening processes. poses to frog biodiversity. Non-riverine wetlands also provide a range of ecosystem services and often constitute a Findings major source of surface water in a region. • Six species were detected during the study There is limited understanding of many of the (Table 1). processes, such as secondary salinisation, that • Wetland salinity did not appear to limit threaten non-riverine wetlands and their amphibian occupancy up to around 3000 biodiversity. An important and charismatic EC or about 6% seawater (Figure 1). Note, inhabitant of fresh wetlands is the frog fauna, EC = µS/cm @25 ºC. a group of taxa that appears to be negatively • affected by secondary salinisation. Frogs are Amphibian biodiversity declined rapidly commonly thought of as indicators of the between 3000 and 6000 EC or about 6% to health of the environment and, accordingly, 12% seawater (Figure 2). may act as ‘sentinel’ species for secondary • We failed to detect any amphibians in salinisation. Studying frogs and their response wetlands beyond 6000 EC or about 12% to changes in salinity may help us to better seawater (Figure 1). understand wetland ecosystems and the threats posed to them. Table 1 : Species detected in the survey of the Wimmera wetlands

Common name Scientific name

Brown Treefrog Litoria ewingii

Common Eastern Froglet Crinia signifera

Mallee Spadefoot Toad Neobatrachus sudelli

Pobblebonk Limnodynastes dumerilii

Spotted Marsh Frog Limnodynastes tasmaniensis

Striped Marsh Frog Limnodynastes peronii Brown Treefrog, Litoria ewingii Photo: Michael Smith

Aims A Victorian Government initiative Mallee Spadefoot Toad, Neobatrachus sudelli Photo: Michael Smith

Implications • Salinities above about 6000 EC are likely to be toxic to the study species. • Secondary salinisation of wetlands regularly exceeds 6000 EC, indicating that human- induced changes in salinity will seriously Figure 1 : Changes in frog species number with increasing salinity. Dotted lines represent the 95% threaten the frog diversity in the study credible intervals. Conductivity has been log region. transformed and was measured as EC. • Frogs are a charismatic fauna that produce easily recognisable acoustic signals and, accordingly, may be well suited to act as ‘sentinel’ species for secondary salinisation. • Some frog species are more susceptible to changes in salinity than others.

Spotted marsh frog, Limnodynastes tasmaniensis Growling Grass Frog, Litoria raniformis. Photo: Michael Smith Photo: Nick Clemann

Published by the Victorian Government Department of Sustainability and Environment Melbourne, August 2006 © The State of Victoria Department of Sustainability and Environment 2006 This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968 . Authorised by the Victorian Government, 8 Nicholson Street, East Melbourne. ISBN 1 74152 567 5 For more information contact the DSE Customer Service Centre 136 186 or Dr Michael Smith on (03) 9450 8612 or [email protected], Arthur Rylah Institute, Department of Sustainability and Environment, PO Box 137, Heidelberg 3084.

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