NARRATION
This may look like the ambush and kidnap of one of our national icons.

NARRATION
But without human intervention, this species may be in serious trouble.
Koalas in Gunnedah are the lucky ones. A couple of decades ago, local farmers like John Lemon planted thousands of trees to fight salinity.

John Lemon
With a bit of help, I've planted nearly every tree down there and I made sure they were koala friendly as well.
NARRATION
Gunnedah is now known as the Koala capital of the world, but habitat loss remains their greatest threat.

Dr Paul Willis
So this tree's in the middle of nowhere, where's it come from?

Dr Dan Lunney
It's walked across the paddock, through the grass to get into this tree and what's surprising is they don't mind crossing a kilometre of paddock, or even two, to cross to a line of trees on the other side. Remarkable isn't it

Dr Paul Willis
yeah

NARRATION
By tracking the koalas to see which trees they prefer, Dr Dan Lunney hopes to provide critical data for future plantings.

Dr Paul Willis
So what do these collars do?

Dr Dan Lunney
Inside the collar we've got a global positioning system and in the global positioning system we've got a recorder and it tells us where the koala is every four hours, 24 hours a day for the next 6 months.
It's energetically expensive to walk across a paddock, it's dangerous to walk across an area where there could be dogs or across a road where there could be cars.

NARRATION
So why do they? In a koala's world, a leaf is not a leaf. Some trees are good for eating, others have high moisture content and bushier trees provide shade on a hot day.Finding out which trees koalas use at night is crucial because this is when they select trees for eating...and when they are most often fatally injured.

Dr Dan Lunney
This is a river red gum and this one is only ten years old which is remarkable - and we know it's a koala tree because we've been able to track it to here - scratch marks - and the other line of evidence is distinctive koala droppings.

Dr Paul Willis
That's solid evidence.

NARRATION
Dan now has two years worth of data to help guide future planting... but his biggest insight into koala survival took him completely by surprise.

Dr Dan Lunney
In 2009 it was a very dry year. There was a heatwave in November, followed by another heatwave in December

John Lemon
For about 8 days the temperatures were well and truly above…thirty five degrees centigrade and the radiant heat from the ground was just horrific...almost every koala was on the ground, at the base of the tree, just exhausted. We came across a koala and we misted it...and the poor little thing just stuck its claws into the back of my hand to make sure that I wouldn't take the water away…. ...

Dr Dan Lunney
So we think the heatwave killed about a quarter of the Koalas in Gunnedah in a couple of weeks.

Dr Paul Willis
Koalas get most of their moisture from the gum leaves that they eat so as heatwaves increase in duration and frequency due to climate change, koalas are going to find it more difficult to survive - but there's another battle looming.

NARRATION
Dr Ian Wallis has been looking at why koalas prefer some gum leaves over others.

Dr Ian Wallis
They're an extremely poor food source, extremely poor. They've got very low concentrations of nutrients in them and that's matched with high concentrations of toxin.
What we're doing here is we're mimicking what's happening in the koala. We've got the leaf in the bag and we've got digestive enzymes in the two beakers and we're looking at how many nutrients the koala would get from the sample of leaves.

NARRATION
Nutrient and toxin levels vary greatly between trees, revealing why koalas are such fussy eaters. Climate change will make them even fussier.

Dr Paul Willis
As carbon dioxide levels rise in the atmosphere, koalas are going to find that their food gets less nutritious and more toxic.

NARRATION
Plants use a protein called rubisco to collect carbon dioxide. With more and more carbon dioxide availble, those protein levels are expected to drop.

Dr Ian Wallis
So that means the nutrient concentration is going to go down in the leaves but at the same time, the toxin concentration is going to go up. We've done experiments where we do push up the CO₂ concentrations and what happens is the carbon-based defences like tannins increase in concentration and both of these things are bad for koalas.

Dr Dan Lunney
They will have to be more selective about which leaves they choose, from which trees. They will have to walk more often, the more often they walk, the more exposed they will be to predation by dogs, being hit by cars.

NARRATION
It's a frightening future for koalas - but with better placement of more nutritious trees koalas may have a hope.

Dr Paul Willis
This is Kate. She's a mummy Koala and she, quite literally, has the next generation in her pouch, but that's a future that we hold in our hands. Good luck.

Story Contacts

Dr Dan Lunney
Senior Principal Research Scientist
Department of Environment, Climate Change and Water, NSW

John Lemon
Natural Resource Project Officer
Department of Environment, Climate Change and Water, NSW

Dr Ian Wallis
Ecologist
Australian National University

Related Info

Koalas and climate change

NSW Koala Recovery Plan

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