Australia's most
endangered snake might need burning
Tuesday, March 24,
2009
Conserving Australia's most
endangered snake might mean lighting more bush fires, ecologists
have proposed.
The last remaining populations of broad-headed snakes are being
threatened by encroaching woodland that is destroying their
habitat, a study by scientists from the University of Sydney and
Stanford University (USA) has shown.
"Broad-headed snakes are only found living in small pockets within
200 km of Sydney, and those small communities are fast becoming
extinct or increasingly more rare," said Professor Rick Shine from
the School of Biological Sciences at the University of Sydney,
co-author on the new paper published online in British Ecological
Society's Journal of Applied Ecology.
As part of a 17-year study investigating causal factors in the
decline of the colourful broad-headed snake, Professor Shine and
colleague Dr Jonathan Webb, also from the University of Sydney,
with Rob Pringle and Mindy Syfert of Stanford University, examined
trends in habitat availability of Australia's most endangered
snake.
Using historical and current images of Morton National Park, 160 km
south of Sydney, the research team compared aerial photographs
taken in the 1940s and 1970s with satellite images taken in 2006 to
ascertain the relative coverage of vegetation and bare sandstone in
each year.
"The results indicate that the amount of bare sandstone, which is
critical habitat for broad-headed snakes and their prey, has
decreased steadily over the past 65 years," Professor Shine
said.
The study also showed that total vegetation cover in Morton
National Park – an area currently inhabited by broad-headed snakes
– has increased over the same 65-year interval.
"The reason for the proliferation of vegetation is not known. In
other parts of Australia, vegetation thickening has been attributed
to altered Aboriginal fire regimes or to 20th-century climatic
change," said Professor Shine.
Dr Jonathan Webb believes increased plant cover may be a problem
for this endangered species due to the increased shading conferred
by the vegetation.
"Prior studies have shown that broad-headed snakes require sunny,
hot-rocks for shelter. Shaded rocks do not reach sufficiently high
temperatures for the snakes to hunt their lizard prey effectively
in the evenings," he said.
"The trend is clear – as the vegetation cover increases, the
snakes' available habitat decreases. Our results indicate that
active management is required if the nation's most endangered snake
species is to be saved from extinction," Dr Webb said.
Such management might take several forms, say the study's authors.
Regular, controlled burns might open up the forest canopy and
prevent tree seedling establishment on the westerly rock
escarpments favoured by the reptiles. Alternatively, if controlled
burns are deemed too expensive or too dangerous to implement, then
foresters might clear overhanging vegetation in areas known to be
important to the snakes.
Although broad-headed snakes would benefit from controlled burns,
the extreme risks of bushfires in Australia must be weighed against
the expected gains.
"As with all decisions in environmental management, the decision
should be made on the basis of the best available information about
the likely costs and benefits of the different strategies. This
includes the potential collateral impacts upon other species of
concern," warns Professor Shine.
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Wiley-Blackwell
Thanks to Wiley-Blackwell for this
article.