Climate Change Threat to Australia’s Koalas

By 1990, there was evidence that rising CO2
levels reduce nutrients in plants. So, even while
elevated CO2 levels can speed growth of plants,
the plant-eaters have had to eat more plant
tissue to gain the same nutrition.

This effect is independent of CO2’s capacity to
retain heat that would have escaped into space,
but the combined two effects will plausibly be
greater than either one alone.

The research on CO2 and nutritional content of
plants has continued for these past 18 years, and
now includes implications for domestic livestock,
humans, and wildlife. Evidence based on koala
research is just the latest finding in a
longstanding topic of interest.

“This change will mean eucalypt species with high protein content will become
unbeneficial to the koala as the so-called
“anti-nutrients” such as tannins bind
the protein making it unusable.”

The Sydney Morning Herald (Sydney, Australia)
  May 6, 2008 – 11:49PM

climate change threatens koalas: expert
The koala is under threat from climate change,
according to new research which shows rising
carbon dioxide levels are killing nutrients in
the plants they eat.

Lab tests have revealed that global warming is
stripping the goodness from eucalypt leaves, and
the University of Sydney researchers behind the
study say the koalas that rely on them don’t have
enough time to adapt to the change.

“What currently may be good koala habitat may
well become, over a period of not so many years
at the rate that carbon dioxide concentrations
are rising, very marginal habitat,” lead
researcher Professor Ian Hume said.

“I’m sure we’ll see koalas disappearing from
their current range even though we don’t see any
change in tree species or structure of the

Prof Hume will present new research at a major
science conference in Canberra showing that
increases in CO2 decrease levels of “good”
nutrients and increase toxic nutrients in
eucalypt leaves.

This change will mean eucalypt species with high
protein content will become unbeneficial to the
koala as the so-called “anti-nutrients” such as
tannins bind the protein making it unusable.

“If there is a significant rise in CO2
concentration in the atmosphere, which we’re
already seeing, that’s going to push the ratio of
nutrients to anti-nutrients even lower by
increasing the concentration of these
carbon-based anti-nutrients,” he said.

When asked how long it would take for koalas to
be affected, he said: “I would’ve thought a few
years ago when we first did these experiments
that you might see something in a hundred years.”

“But at the rate at which things are going, I
suspect that we might see changes within our
lifetimes,” Prof Hume said.

He will tell the Academy of Sciences conference
that koalas had “nowhere near enough time” to
adapt to the changes in nutrient content.

They may be forced to travel in search of more
nutrient-rich species, increasing their risk of
being hit by vehicles or eaten by predators, the
researchers warned.

The team believes the eucalypt will also be
affected by rising temperatures, with some so
sensitive to heat that even a one-degree shift
will affect their growth.

The marsupials could be left with less
temperature-sensitive species that are not
suitable for koala feed.

The group studied the four marsupials that eat
eucalypt foliage – koalas, the greater glider,
common ringtail possum, and common brushtail
possum – and found koalas most sensitive to the

© 2008

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