Australia Yearbook - 2009-10

Frogs as indicators of aquatic
ecosystem health
Frogs are very sensitive indicators of aquatic
ecosystem health. Frog populations have
decreased significantly over the last 15 years,
with 4 species of frog extinct (including both
the southern and northern gastric-brooding
frogs), 2 critically endangered, 14
endangered, and 12 listed as vulnerable.
While some of this decline may be attributed
to the Chytrid fungus, human impacts are
likely to have exacerbated the problems
frogs are experiencing.
5. NUMBER OF NATIONALLY IMPORTANT
WETLANDS AND NUMBER WITH THREATENED
WATER REGIMES AS AT 2001
State or Territory
New South Wales
Victoria
Queensland
South Australia
Western Australia
Tasmania
Northern Territory
Australia Capital
Territory
External Territories
Total
Total
number
of sites
178
159
181
69
120
89
33
13
9
851
Number of
wetlands
with
threatened
water
regimes
38
57
42
19
51
13
7
4
—
231
— nil or rounded to zero (including null cells)
Source: Davies et al.2001.
Southern Gastric-brooding Frog.
What are the major threats to
biodiversity in Australia?
Human threats to biodiversity in Australia are
numerous. They range from localised impacts
such as clearance and fragmentation of
habitats, unsustainable and destructive use of
resources, and pollution, to impacts on broader
scales, such as the introduction of feral species,
deteriorating water levels and quality and the
consequences of a changing climate. All of
these impacts result from changes to the
environment and the ecosystems which
support biodiversity. Taken collectively, the
cumulative effect of these impacts is a major
threat to Australia's biodiversity.
Loss, fragmentation and
degradation of habitat
One of the most significant factors in
determining the health of ecosystems is the
extent and quality of native vegetation. The
locations where species are declared to be
threatened correlates closely with areas where
native vegetation has been extensively cleared
and in regions where intensive development
has occurred (Figure 7). As urban areas expand,
development continues to encroach on
ecosystems surrounding cities and biodiversity
of these areas is increasingly being degraded or
lost.
Vegetation clearance has both immediate and
longer-term impacts on biodiversity and
ecosystems. A Queensland-based review
estimated that clearing of 1 square kilometre of
woodland results in the deaths of about 3000
individual birds, 20,000 reptiles and 45,000
trees. 13
It is not just the direct loss of vegetation that
has impacts on species. Fragmentation of
ecosystems, where species lose the ability to
move between remaining areas of habitat, has
longer-term impacts on the survival of many
species. Isolation of individuals or groups in a
population leads, over time, to a reduction in
the genetic diversity of the entire population
12 Year Book Australia 2009–10