[CDU eNews] -TROPICAL SAVANNAS UNDER THREAT

[Peter.Hurt at cdu.edu.au]

Tropical savannas under threat

Drought, fire and overkill have forged the Australian landscape for more
than 40,000 years - but the recent spread of African grasses, such as gamba
grass, could radically alter it even further.

That's the warning from Professor David Bowman, Director of the Key Centre
for Tropical Wildlife Management at Charles Darwin University.

Professor Bowman said these grasses, including gamba grass, para grass,
mission grass and buffalo grass, were invading large areas of the Top End,
wiping out native grasses and shrubs.

"These grasses can produce up to four times the fuel load of native grasses
and represent a serious threat to our traditional ecosystem," Professor
Bowman said today.

"The irony is that this continent has been shaped by fire and the native
grasses and shrubs have developed a remarkable tolerance to it. However,
these weeds build up such huge fuel loads that they cause terrible fires
that are able to outstrip the resilience of our native acacias and
eucalypts.

"This is truly an issue of national concern because it involves the
potential transformation of vast tracts of the continent from an Australian
landscape into an African savanna. It has serious implications for
Indigenous communities, tourism and graziers."

Professor Bowman will put the latest 'invasion' into historical perspective
tomorrow (Friday) when he delivers a seminar at the university.

"The onset of the monsoon climate millions of years ago enabled the flora
and fauna to adapt to the climatic extremes of tropical wet and arid dry
seasons.  Lightning fires became so common the flora developed remarkable
adaptation to recover from this disturbance.  Through the process of
evolution these 'extreme' conditions eventually became 'normal' for the
plants and animals."

However, Professor Bowman believes the colonisation of Australia by humans
40,000 to 50,000 years ago changed fire patterns and, combined with hunting
pressure, contributed to the extinction of many large marsupials.

"The big guys simply couldn't adapt to the changes wrought by humans.
Eventually the system settled down - until the environmental upheavals
caused by the last 200 years of settlement.

"Those that survived the Aboriginal impact have since suffered greatly from
the chronic ecological impacts that followed European settlement, such as
the introduction of predators, stock and changed fire regimes, particularly
the African grasses that have triggered a new grass-fire cycle."

Professor Bowman's lecture, entitled Extreme evolution and adaptive shock -
the forging of the Australian biota by drought, fire and overkill, will be
given in Room 22.01 on the Casuarina campus of Charles Darwin University at
12 noon on Friday, May 13.

Professor Bowman is available for interview.

Peter Hurt
Media Manager
Charles Darwin University
Tel: 08 8946 6019 or 0438 466 439

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