An antidote to despair

Published 17 Sep 2019 

Rather than lose hope when eucalypts started dying in central Victoria, Bush Heritage scientists came up with an innovative solution using future climate scenarios.

Bush Heritage volunteer Dr Garry McDonald. Photo Kate Thorburn.
Bush Heritage volunteer Dr Garry McDonald. Photo Kate Thorburn.
In the middle of a cleared paddock on a cold and foggy winter morning, Dr Garry McDonald and several Bush Heritage staff huddle together to run through their game plan one last time. Then, tray by tray, they start unloading their precious cargo from the backs of their white utes.

The trays are filled with Grey Box and Yellow Box seedlings that have been germinated from seeds collected at different locations (known as provenances) across south eastern Australia.

After being carefully cleaned, the seeds were cultivated in a nursery until big enough for planting here on Nardoo Hills Reserve, where large tracts of woodland have suffered mass dieback.

Dr Matt Appleby with a tray full of seedlings. Photo Amelia Caddy.
Dr Matt Appleby with a tray full of seedlings. Photo Amelia Caddy.
The team – led by Garry, a Bush Heritage volunteer and University of Melbourne researcher, and Dr Matt Appleby, Bush Heritage’s senior ecologist for the South East – will plant over 9000 of these seedlings before the week is done.

The revegetation is both refreshingly proactive and mind-blowingly complex. The cleared paddock has been divided into 18 blocks, half of which will be planted with Yellow Box and half with Grey Box. Each block is divided into 25 plots, and those plots are split further according to the different provenances.

Ensuring that the seedlings go in the right plots is a logistical nightmare. But it’s necessary because this planting is going to form the basis of a long-term experiment that will hopefully see scientists revisiting the plots regularly for decades to come.

Nardoo Hills is a 1207-hectare Bush Heritage reserve located about a three-hour drive north of Melbourne.

Dja Dja Wurrung people refer to parts of this area as upside-down country – a reference to the gold rush of the mid-1800s that saw waterways diverted, woodlands cleared, and huge quantities of earth upended.

The Kara Kara-Wedderburn region, where Nardoo Hills is located, is one of the few parts of central Victoria that still retains large tracts of uncleared woodlands, and it's a refuge for many species as a result. But today there's another, more insidious threat to woodlands in the Kara Kara–Wedderburn region, and possibly farther afield: climate change.

Dieback on Nardoo Hills (in foreground). Photo Amelia Caddy.
Dieback on Nardoo Hills (in foreground). Photo Amelia Caddy.
Over the past five to 10 years, about 100 hectares of Grey Box and Yellow Box trees – almost 10% of the reserve – have collapsed.

The dieback events followed long heatwaves such as the two periods of five consecutive days over 40 degrees in January and February 2014. Combined with low rainfall, these heatwaves were too much for the Nardoo trees, which have adapted to a less extreme climate.

"It's heartbreaking to look at," says Garry. "Now, when you stand on top of the hills and look north, you just see a mass of dead, dying or very stressed trees."

The cumulative losses sparked an urgent need to act; without new habitat soon, many woodland birds, insects and other animals at Nardoo Hills would suffer. But it made little sense to condemn more trees to the same fate. Instead, Garry and the team used climate modelling to pinpoint regions with climates analogous to the hotter, drier climate that is predicted for Nardoo Hills in 30-70 years’ time, based on two different emissions scenarios.

They cross-referenced this list with records of Grey Box and Yellow Box populations and set about collecting seed from areas such as Fifield, Junee and Narrandera, in central-western NSW, as well as locally.

“Our hope is that the different provenance seedlings will grow and cross pollinate with the local provenance trees to generate maybe tens of thousands of new seedlings that are more robust and resilient in the face of a harsher climate,” says Garry.

With the seedlings lined up next to each other in the cleared paddock at Nardoo Hills, their genetic diversity is obvious; the different provenances vary greatly in size and appearance from one another.

As the seedlings grow, Bush Heritage and other scientists will closely monitor their growth and survival rates. The data will be made publicly available to inform future climate-related revegetation projects as Australia’s climatic zones shift and other dieback events inevitably occur.

Having spent over two years looking at future climate scenarios in preparation for this project, one could forgive Garry for despairing at the crisis we find ourselves in. But he says quite the opposite has occurred.

“The nice thing about this project is that, rather than sitting back and watching the environment unravel, I’m actually taking tangible actions to protect against those impacts.”

Bush Heritage acknowledges the support of its volunteers and project partners, environmental not-for-profit Greenfleet and the Aborline Nursery in Hamilton, Victoria.

Creating a climate resilient woodland

1 Climate change scenarios for Nardoo Hills

We came up with three future scenarios for Nardoo Hills – ranging from a slightly warmer SCENARIO 1 to a much hotter and wetter SCENARIO 3 – based on a range of emissions pathways and time periods.

Average maximum temperature

Average annual rainfall

CURRENT 2019
23.2°C
470mm

Target species for revegetation:

Grey Box
Eucalyptus microcarpa

Yellow Box
Eucalyptus melliodora

SCENARIO 1* 2050 RCP 4.5
24.4°C
475mm

Similar provenances:

Mathoura (NSW)

Junee (NSW)

SCENARIO 2* 2090 RCP 4.5
25.2°C
451mm

Similar provenances:

Quorn (SA)

Narrandera (NSW)

SCENARIO 3* 2090 RCP 8.5
26.0°C
521mm

Similar provenances:

Fifield (NSW)

Condobolin (NSW)

What are RCPs?

‘Representative Concentration Pathways’ are the four greenhouse gas concentration projections used in the IPCC’s fifth assessment report: RCP 2.6, 4.5, 6 and 8.5. They cover a range of emissions scenarios.

RCP 8.5 is the most dire and what we would likely see from a ‘business as usual’ approach.

RCP 2.6 is the most ambitious, and would require strong and urgent action.

* These climate scenarios are based on CSIRO/BoM Climates Futures models. Visit climatechangeinaustralia.gov.au for more information.

A map showing the sources of our seed stock.

2 Sourcing seed from different climates

Grey Box and Yellow Box seeds of different provenances were collected, where possible, from regions with climates similar to the three future scenarios outlined above. Seeds from the local Nardoo Hills area were also collected.

3 Future proofing through cross pollination

Each provenance will be adapted to cope with a different temperature range and rainfall. Our hope is that, in decades to come, cross breeding will produce a far more genetically diverse and resilient woodland.

Grey Box provenances
Temperature and rainfall adaptations

Grey Box provenances graphic

Yellow Box provenances
Temperature and rainfall adaptations

Yellow Box provenances graphic
more resilient woodland