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Cleaning up in Maningrida after Cyclone Monica: African mahogany
trees were vulnerable to the force of winds.
Photo: Deb Bisa
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ECOLOGIST Greg Calvert is keen to hear from people regarding
tree loss and resilience during Cyclones Monica and Larry. Greg is
planning a book on cyclones and trees, how to minimise damage to
house and property through good plant selection and gardening
practices.
The book will list good tree and plant choices for urban gardens
in northern Australia and those which are not so good. The choices
will be based on information collected from several cyclones
including Tracy, Althea, Charlie, Justin and Tessi as well as the
latest two.
The projected book will also discuss ecological impacts of
cyclones; how cyclones contribute to the structure, dominance and
diversity of different ecosystems, and the land management
challenges presented by cyclones.
Greg, who is currently based at Jabiru, has conducted a recent
survey of around 400 fallen trees around the township. Jabiru
sufferred the last dying gasp of Monica, so it was around a
Category 3 by the time it hit. It still had the energy to lay waste
to most of the town’s shallow-rooted African mahogany, as
well as numerous black wattles and river red gums.
Many tropical towns and cities are assessing the cyclone
resistance of future plantings in the wake of these
cyclones,” Greg said. “The aim is to minimise damage
caused by falling trees while at the same time acknowledging the
value of some resistant trees in preventing damage—by
catching flying debris and acting as wind breaks.”
As far as good species goes, research is showing plants that
have evolved in high-energy environments, such as those that grow
along the edges of fast-flowing rivers and streams tend to be very
resilient towards cyclones.
“These plants are subjected to battering by floods and
tend to have very strong root systems and seem flexible enough to
move and bend,” explained Greg. “Also there are species
that will sacrifice small branches which reduces their wind
resistance; some trees will lose their entire crown, which is not a
bad sacrifice if you get to keep your roots in the
ground.”
Species choice is just one element though; trees can also be
made vulnerable due to poor garden management such as shallow
watering or factors such as termite damage.
“For every one of these trees that you see doing well, you
also see examples of where they’ve gone horribly
wrong!” said Greg. “It’s a risk assessment that
everybody needs to make on their own houses. With some trees the
consequences are high.”
