From little trees, climate resilience grows

Bush Heritage acknowledges the Traditional Owners of the places in which this podcast was recorded and in which we live, work and play. We recognise the enduring relationships they have with their lands and waters and pay our deepest respects to elders past and present.

00:17 Garry McDonald: OK, everyone buckled up?

Yep, Yep. Let's go.

00:25 Eliza Herbert: There's no feeling like the anticipation you get when you're heading from the city to the bush, each bend, taking you further away from industrial outskirts on the city's edge and closer to tree-lined vistas and big skies. 

Today, that's exactly what we are doing. We are driving from Melbourne to a big, beautiful patch of bushland right in the middle of Victoria. But this isn't a day trip just for fun. We're heading out to assess the health of some very important trees – Grey Box and Yellow Box eucalypts. These two species form the eucalypt backbone of a nature reserve of great ecological and cultural significance. 

But they’re under threat from climate change and are now the focus of a great experiment, which scientists hope will lead to more resilient woodlands for future generations. This is Big Sky Country, a podcast by Bush Heritage Australia. I'm your host, Eliza Herbert, and today we are talking about trees.

01:50 Garry McDonald: Trees are incredible. They're such a central feature of our landscapes. They are the lungs of our landscapes. They generate oxygen, they take in carbon dioxide, they provide habitat, they provide shade. They are there - some trees have been there for hundreds of years. They could tell more stories than a whole community of us could tell. They are a remarkable thing.

02:15 Eliza Herbert: But before we get to the trees, let's talk about where we are going. Nardoo Hills - a 1,2107 hectare nature reserve on the lands of the Dja Dja Wurrung people of the Kulin nation.

02:26 Harley Douglas: My name is Harley Douglas and I am a Djarra man. I have grown up fully on Dja Dja Wurrung Country, born and live here now.

02:36 Eliza Herbert: The Dja Dja Wurrung Traditional Owners have walked this country for many thousands of years. It was their supermarket and their classroom, and signs of their enduring custodianship are found across the landscape. Harley is a project manager with Dja Dja Wurrung Enterprises and has been working closely with Bush Heritage on a number of projects at Nardoo Hills.

02:56 Harley Douglas: There's a lot of cool things at Nardoo Hills. There's a lot of cultural heritage. There's scar trees. I think we identified a ring tree last time I was there, and clay balls as well, which were instruments used to help cook. And there's also a natural soak as well, which was very significant to our people in those, sort of dry areas that would have prolonged droughts.

03:18 Eliza Herbert: When you stand atop some of the high points at Nardoo Hills, you see undulating slopes with Wedge-tailed eagles soaring above and robins flitting in the breeze. It’s a beautiful part of the world. A refuge for plants and animals in an area that has undergone great disruption.

03:34 Harley Douglas: The main species of animal that you'd see there is Guri, the kangaroo, Guri means kangaroo in Djarra. But there should be Emus everywhere in that landscape. But because farming is so intensive they've been run off the land. Barramul is the word for Emu.

03:51 Eliza Herbert: Since European settlement, more than half of Victoria's native vegetation has been lost to land clearing. When Bush Heritage purchased Nardoo Hills over 15 years ago, the goal was to safeguard what was left of the temperate woodlands - Australia's most threatened wooded ecosystems. And to continue to provide habitat for native species, including birds, reptiles, insects and arboreal mammals that depend on them. 

But since then a new problem emerged, one that threatened to upend this delicately balanced ecosystem. Trees at Nardoo Hills began to die.

04:24 Garry McDonald: The Reserve Manager began to notice right back in 2008 and certainly in 2014, some of the the really significant trees - old trees, began to die, or the at least the canopy collapsed and died.

Eliza Herbert: That's doctor Garry MacDonald, an entomologist and researcher with the University of Melbourne.

Garry MacDonald: And I remember standing here five years ago, my first view of landscape, and there were just basically a whole lot of white sticks sticking out of the ground.  

Eliza Herbert: When Gary heard about these trees, he started volunteering with Bush heritage in an effort to understand what exactly was happening.

05:00 Garry MacDonald: We've lost a lot of trees and among them, most notably we've lost a whole lot of big, old mature trees that contain the hollows for birds and reptiles and all the twisting and turning bark creates habitat for all sorts of organisms. So that's kind of being lost as we speak.

05:26 Eliza Herbert: And you know, being out here, you can hear the leaves rustle, there's a really beautiful sound to being in the Bush. But I have heard that, hypothetically, if you put your ear up to a tree, you could hear the sound of it dying.

Garry: Yes. Well, look, sadly, there is truth in that. True physiologists tell us that the process that leads to the canopy death is that the tubes - the Xylem, that draw up moisture from the ground into the leaves to keep the leaves cool and keep the tree living. Those tubes break under enormous vapor pressure strain - when the canopy of the tree is under extraordinary pressure and the root system is struggling to find water. A bit like, you can imagine, you know, sucking through a straw and a glass. This straw sucks in and it collapses on itself. Well, so does the Xylem feeding these leaves. But, of course, it doesn't have that elasticity about it. It doesn't spring back, and they crack. And although I haven't heard it, physiologists tell us that you can hear the popping of the Xylem under these extraordinary conditions.

06:41 Eliza Herbert: Another way of looking at this phenomenon is like when you go for a big run, your body's water content drops and you become thirsty and dehydrated. If you don't get water, you enter a state of stress. To most of us listening, the thought of not finding a drink is unimaginable. But to these trees it's a very real future reality. What got scientists worried was that this wasn't a one-off event.

07:12 Dr Kate Fitzherbert: The reason that we got the die back was due to the climatic conditions and these are just going to intensify over time. We've been watching small changes happening in the landscape, but now we're starting to see these much more profound changes.

07:29 Eliza Herbert: Dr Kate Fitzherbert, leads Bush Heritage’s science team. She’s been working closely with CSIRO and the Bureau of Meteorology to understand how climate change could impact landscapes across Australia throughout the next century. This includes looking at things like what temperatures, rainfall, fire conditions and extreme weather events are predicted. And it's all based on the best data we have about what different emission scenarios could lead to. 

If you're anything like me, thinking about our future under climate change can be anxiety inducing. This type of modelling was something I had never heard of, but it gave me great comfort to know that Australia's leading scientists were on the job.

08:08 Kate: Understanding the impacts of climate change for us, is critically important, because if we're going to adapt to the impacts of climate change, we're going to manage for climate change, we have to understand what those changes are going to be.

08:22 Eliza Herbert: What they found was that climate modelling for Nardoo Hills predicts an alarming scenario. It is likely to experience hotter temperatures, more extended periods of hot days and less rainfall, particularly during winter and spring.

08:36 Kate: Which is a critical time not only for agricultural production, but also for natural systems where they're gearing up for that big Spring growth, and it’s the driver of all that productivity for the year. So as we lose some of that rainfall, the numbers of days get hotter, the whole systems are going to start going under stress.

09:00 Eliza: So if ecosystem function was to be restored for the reserve, then Bush Heritage had to consider replacing trees into the landscape. And, more importantly, it had to think really carefully about the genetic potential of those trees it was going to replace. 

That's where Gary comes in. Working with Bush Heritage staff Gary developed a unique experiment, based on the climate modelling, to plant over 11,000 carefully selected seedlings at Nardoo Hills, a process known as climate-adjusted provenancing.

09:28 Garry: So we go to those areas that are already as hot and dry as Nardoo will be. And if the records tell us that there are Yellow Box of Grey Box in those environments - the two species that we're most concerned about here - then we've collected seed from those trees and we've introduced them into an experiment, where we can track individual mother trees and those regional groups of trees we call provenances.

10:00 Eliza: Seedlings were grown from seed collected from 4 different areas, from mid North, SA and Central NSW, where Yellow Box and Grey Box have already adapted to the hotter, harsher environments that Nardoo Hills is predicted to be like in 50 to 70 years when the trees reach maturity.

10:16 Garry: And we compare them in a big, what we call a randomised block design, so we can see how the different mother trees and provenances behave in different parts of the landscape.

10:30 Eliza: It’s these seedlings that we’re checking on at the reserve today. Unlike many field experiments, this one is designed to persist and be monitored for many decades, allowing the trees to pollinate, bear fruit and produce several generations of trees with increasing fitness against ever more severe climates. 

As part of this monitoring each tree was tagged with its own unique label, which details its provenance, which helps to understand whether the climate-adjusted provenances do better under future conditions than the trees from the local provenance.

10:59 Eliza: Gary, what are you doing right now?

11:01 Garry: Oh, look I'm just... we’re replacing some of the labels on plants that have... in this case birds have chewed away at the label. So we're just... once they naw away at the QR code, they're not readable. So, as long as the cockatoos don't play havoc with them, which is what they're doing.

11:26 Eliza: In a project of this scale, there's many things to consider. One of them is all the things that can go wrong.

11:32 Garry: Well, as anyone who's ever undertaken an experiment in the field would know, there’s always challenges. And actually climate weather's probably always the number one. So, we cracked a corker. We designed all this experiment. We started collecting seed in 2017, we designed it in 2018. We propagated the seed in 2019, we planted in mid-2019 and spring 2019 we didn't receive a single drop of rain. And by early summer 2019, many of our trees had died. So it was a major setback.

But it was only the the first of two plantings. We did another planting last year, 2020. And, I have to say, we did lose a lot of plants, but there's still enough statistical power in the experiment to draw conclusions about both the provenances and probably, possibly, the influence of individual mother trees within each provenance comparison.

12:41 Eliza: Another important thing to consider is the people power. The project is a partnership between carbon offset of Green Fleet, Arborline Nursery, and countless volunteers like Haley, who is out with us tagging seedlings today.

12:55 Hayley: Today we're putting labels on some of the plants that missed out on labelling beforehand, whether it be because they've miraculously survived, when we thought they were dead or labels have been taken off the plants by birds or roos, things like that. We're putting them back on.

13:11 Eliza: And why is the labelling important?

13:14 Hayley: So, we need to be able to track the provenance of the individual plants - where they've come from originally. We need to be able to track the mother plant that they were collected from. Yeah, just being able to track them.

Eliza: And another thing to consider with the success of this project over the next 50 to 70 years is the continued health of the landscape at large and the people within it.

13:38 Harley: We need people in the landscape to look after it. The position of a lot of Djarra people in climate change is that we've adapted to the climate and lived within it. Obviously within the last couple of 100 years this has been exacerbated and sped up at quite a frightening pace. And that's why projects like the ones Bush Heritage are managing and a lot of the work that Dja Dja Wurrung and Djandak are delivering are so important to changing ourselves within the landscape, but also connecting people to those landscapes. 

Because the landscapes aren't good to anyone if we're just putting a fence around it. We need people to be interacting with things and understanding why it's important to protect and preserve it. We need people to become more familiar and intimate with the nature and their surroundings, and then that way it can be passed on intergenerationally and taught in in a much more meaningful way.

14:42 Eliza: So we've got a moon above us now. It's nearing the end of the day and we're standing near some of your favourite trees. Can you describe these trees for us?

14:51 Garry: Well, they're beautiful trees, they’re about 1/2 a meter tall on average, a bit taller. Almost without exception they are all thriving. They’re looking terrific. They've got some terrific growth on them, a bit of branching. Yeah. And just sort of loving it really. Just terrific.

15:13 Eliza: According to Gary, we have a window of time in which to experiment with different ideas to cope with climate change. This project is still very much in its infancy. There's still a lot of unknown variables, but ideally the trees will pollinate in 10, maybe 15 years’ time and the project will create a blueprint for other land managers to follow.

15:32 Garry: The climate scenario is a bit bleak, but I think it's uplifting to think that we can do things to enable, at least our reserves and the surrounding landscapes, to have better tools to cope with those more extreme climates that are coming.

15:46 Eliza: But for the moment, to be honest, it's just really nice being out here on Dja Dja Wurrung Country with habitat like this that still exists, with people dedicated to making a difference.

15:57 Garry: I mean, what a privilege to be on a reserve that is really a remnant of the bush that we all love. And it is magic – it is absolutely magic to be among the trees. I'm a great lover of trees. But of course, there's the birds and the animals and the insects that are totally dependent on these trees, they're all around us. At different times of day the birds come in full chorus. And what a privilege to be sitting quietly among this biodiversity and and taking it all in.

16:36 Eliza: Big Sky Country is a podcast by Bush Heritage Australia - a conservation not-for-profit that buys and manages land and partners with Aboriginal people to protect our irreplaceable landscapes and magnificent native species forever. To learn more about our work, sign up to our newsletter or follow us on social media via the links in the show notes.

Special thanks to Gary MacDonald, Harley Douglas, Dr. Kate Fitzherbert, Hayley Syme, and Justin McCann. This episode was produced by myself, Eliza, Herbert, and Kate Thorburn with advice from From Liz Keane. The theme music is Invertebrate City by the Orb Weavers and audio was mixed and mastered by Mitch Ansell.