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As native birds continue to lose their homes due to
the spread of the Australia’s cities, scientists are urging city planners
and householders to help save them by planting more Australian
trees.
A world-first study in the Australian national
capital shows that the amount of native trees on suburban streets has a
big effect on the numbers and types of birds in the
area.
“We found that suburbs with more than 30 per cent
native street trees have 11 per cent more bird species of all types than
those with exotic street trees,” say Dr Karen Ikin and Professor David
Lindenmayer from The ARC Centre of Excellence for Environmental Decisions
(CEED) and The Australian National University.
“More birds were also found in nature reserves next
to the suburbs. This shows that how we manage our urban areas has a
significant effect on wildlife in surrounding
locations.”
The researchers surveyed 66 bird species at 40
locations across Canberra and grouped native birds by their tolerance of
urbanisation.
“With the exception of native birds that avoid urban
areas, a significantly higher number of bird species – both feral and
native – were found in suburbs with more than 30 per cent of Eucalyptus
trees,” says Dr Ikin.
“Exotic trees like oak trees, elms and plum trees are
the most popular choices in current street tree plans,” the researchers
say. “While these trees have their benefits, such as providing more sun in
the winter or bushfire protection, our study reveals that they may have a
negative impact on native birdlife.”
Eucalypts, on the other hand, have a crucial role in
maintaining biodiversity, says Dr Ikin: “They provide food, nest sites and
shelter for birds via foliage, flowers, bark, canopy air spaces and leaf
litter.
“Our previous study showed that parks with large
eucalypts – ones with a trunk diameter over a metre – had up to three
times the number of bird species than parks with smaller trees,” she says.
“Along with this research, we now have good science to support the
planting and retention of native trees, especially large ones, in urban
areas.”
“While there are safety risks in keeping big trees, a
lot of wildlife, including endangered animals such as the superb parrot
and the tiger quoll, depend on them,” Prof. Lindenmayer says. “So instead
of removing these old trees, we can prune them, create zones or put up
safety warnings.”
“We can also proactively plan for future large trees,
so that the younger can replace the over-mature ones. In addition, these
trees can be given greater legislative protection,” the researchers say.
“Householders can also make a big difference by planting native shrubs and
trees in their gardens.
“Urbanisation is unavoidable, but our studies show
that there are ways to lessen its negative impact on Australia’s native
wildlife – we just have to think more carefully about how we design our
suburbs,” they say.
“If we want to increase biodiversity in urban areas,
birds are an easy way to start – native street trees can benefit ‘native
favourites’ such as the superb fairy-wren and crimson rosella. We can also
plant more shrubs, keep more tree logs and leaf litter in parks and
private gardens for native birds that currently avoid urban areas, such as
the threatened white-winged triller.
“Research shows that people enjoy seeing and hearing
birds around their home, work and recreational spaces, even if they are
not interested in what the individual species are. So having charismatic
and colourful ‘native favourites’ that ordinary people can recognise can
improve their well-being.”
The team’s paper “The influence of native versus
exotic streetscape vegetation on the spatial distribution of birds in
suburbs and reserves” by Karen Ikin, Emma Knight, David B. Lindenmayer,
Joern Fischer and Adrian D. Manning appears in the journal Diversity
and Distributions. See: http://bit.ly/Wx7ysn
CEED is the Australian Research Council Centre of
Excellence for Environmental Decisions. CEED’s research tackles key gaps
in environmental decision making, monitoring and adaptive
management.
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