Wetlands,
Biodiversity and Salt
Frogs
Overview
Non-riverine wetlands are particularly
important habitat for local and regional
biodiversity. The successful management of
these ecosystems relies on understanding
changes in wetland function and biodiversity in
response to a range of threatening processes.
Non-riverine wetlands also provide a range of
ecosystem services and often constitute a
major source of surface water in a region.
There is limited understanding of many of the
processes, such as secondary salinisation, that
threaten non-riverine wetlands and their
biodiversity. An important and charismatic
inhabitant of fresh wetlands is the frog fauna,
a group of taxa that appears to be negatively
affected by secondary salinisation. Frogs are
commonly thought of as indicators of the
health of the environment and, accordingly,
may act as ‘sentinel’ species for secondary
salinisation. Studying frogs and their response
to changes in salinity may help us to better
understand wetland ecosystems and the
threats posed to them.
August 2006
We described changes in frog diversity in nonriverine wetlands along a salinity gradient in
the Wimmera region – an area that is
threatened by secondary salinisation. This
information was collected to allow us to better
understand the threat that increasing salinity
poses to frog biodiversity.
Findings
• Six species were detected during the study
(Table 1).
• Wetland salinity did not appear to limit
amphibian occupancy up to around 3000
EC or about 6% seawater (Figure 1). Note,
EC = µS/cm @25 ºC.
• Amphibian biodiversity declined rapidly
between 3000 and 6000 EC or about 6% to
12% seawater (Figure 2).
• We failed to detect any amphibians in
wetlands beyond 6000 EC or about 12%
seawater (Figure 1).
Table 1: Species detected in the survey of the
Wimmera wetlands
Brown Treefrog, Litoria ewingii
Photo: Michael Smith
Aims
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
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 humaninduced changes in salinity will seriously
threaten the frog diversity in the study
region.
• 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
Photo: Michael Smith
Figure 1: Changes in frog species number with
increasing salinity. Dotted lines represent the 95%
credible intervals. Conductivity has been log
transformed and was measured as EC.
Growling Grass Frog, Litoria raniformis.
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 michael.smith@dse.vic.gov.au, Arthur Rylah Institute, Department of
Sustainability and Environment, PO Box 137, Heidelberg 3084.
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the Wetlands, Biodiversity and Salt project can be found by following ‘Research Themes’ to ‘Salinity and Climate change’