

Posted August 03, 2018 14:20:44

As parts of the country face the toughest drought in people's lifetimes, tree species that can assist in water and soil management have a renewed purpose.

Need to raise your water table, stabilise your soil or grow an alternate fodder source in arid conditions?

There is a tree — or grass — for that.

Fran Bodkin, a Dharawal elder who has degrees in environmental science, geomorphology and climatology, wrote the Encyclopedia Botanica by hand when pregnant and confined to bed rest.

She said farmland could be stabilised naturally to help it cope with a changing climate, and it was as simple as planting a few trees.

Using tree teamwork to find balance

Trees are sophisticated pieces of engineering, purpose-built for their habitat.

But they work best as a team and can be destructive if planted as a single species.

"One of the things that really bugs me is when we plant only one [species of] gumtree," Ms Bodkin said.

"It gives them no support because our ecosystems grew up with each other for millions and millions of years and they have learnt to support each other.

"We separate them out and expect them to do the same thing that the [former multi-species] community did. They need each other."

An ecosystem, by definition, is about balance. In times of severe weather stress, this balance is especially effective at protecting and even encouraging natural resources such as water and soil.

It is possible for anyone to re-establish this balance.

Ms Bodkin lists three native trees that people experiencing drought could plant now and in time, the trees would raise their water table, improve soil quality, encourage insect and bird populations, and provide fodder for stock.

"The Eucalyptus populneus in company with the Geijera. There's Brachychiton populneus too," she said.

If you get those three — the Geijera, the Eupcaplytus populneaus and the Brachychiton growing near [them] — it's really good.

"The Brachychiton brings the water up, the eucalyptus attracts the good insects and birds in, and the Geijera provides the fruit for the birds.

"They are all native to west of the [Blue] Mountains except the Brachychiton. It grows everywhere."

Drought-busting species to plant right now

When planted together, these species will improve the soil, increase the ground water system, and improve air quality.

The water tree

The Brachychiton populneus, or kurrajong tree, is a natural water bottle.

The species raises the water table and brings moisture to neighbouring tree roots.

Its branches can also be cut down and used as fodder for sheep and cattle in times of drought — its leaves and branches have exceptional moisture content, which is valuable to stock in the dry.

"The brachi would provide the water for us too when we were travelling, from the branches and the roots," Ms Bodkin said.

"If you take it from the trunk the water leaks out, but if you take it from the end branches or the end roots, you're fine and the tree survives."

The pollinator

Eucalyptus populnea, or poplar box, is a eucalypt species native to eastern Australia.

Its blossoms attract insects and birds, boosting pollination and, incidentally, honey production.

Its broad leaves reflect sunlight off soil and stock during dry times.

The cooling agent

The Geijera, commonly called the wilga or native willow, is shrub-like.

"A nice tree to sit under and have a picnic," Ms Bodkin said.

It has moist leaves and is a cooling tree for stock. Sheep can graze under the tree and create their own shade canopies.

The wilga thrives in semi-arid conditions — so much so it will not flower if grown in shade.

The soil warrior

Themeda, or kangaroo grass, is a native grass that is edible to humans and excellent fodder for cattle and sheep.

Themeda binds distressed soils together, preventing topsoil blowing off in drought-related winds.

It can also restore soil quality, but its greatest trick is wild — Themeda produces a hormone that can get rid of weeds.

The support crew


Another soil star is the casuarina. Its thick needle litter allows soils to retain their moisture, prevents soil erosion and supresses weed species.

"As a genre, they grow right across Australia, so you can always get a casuarina that fits in a particular spot," Ms Bodkin said.

"The casuarinas are very, very good. They are beautiful little homes for the bugs in the soil."

Acacia aneura

Mulga wattle's wide root systems hold distressed soil together and prevents erosion.

Extremely drought-tolerant, the mulga's seeds and flowers are edible.

Bursaria spinosa

"Bursaria, its little name is spinosa, is a plant that is necessary for eucalyptus," Ms Bodkin said.

"It helps the eucalyptus to survive."

A small, thorny and not especially scenic shrub, spinosa grows at the base of eucalypts, attracting a beetle that preys on cut leaf moth larvae, as well as aerating the soil.

Cut leaf moth larvae eat eucalypt root tips, killing the tree.

While prickly, the plant is edible to stock and the leaves are a natural sunblock when rubbed on the skin.

Returning to cultural land management

The impact of moving away from a cultural land management system such as that proposed by Ms Bodkin was seen in Greece recently.

Greece used a cultural land management system that ensured the land was fertile and fireproof for thousands of years.

But recent wildfires there demonstrated the might of misplaced trees species and abandoned land management.

University of Tasmania environmental change biology professor David Bowman has studied Australian evergreens, such as eucalyptus and acacias, to understand how they withstand Australia's climate extremes.

He also studies cultural land management practices and the impact they can have in the face of climate change.

"There was a particular system that worked in the Mediterranean," Professor Bowman said

"They used sheep and goats and had vineyards and clearings. It was traditional and it was a cultural landscape."

But the recent fires were facilitated by the mighty gum growing as a single species being used out of context.

"[Eucalypts] have created all sorts of problems [in Greece]," Professor Bowman said.

"[They have] increased the flammability of the landscape and affected water supplies because they are so thirsty.

"People hate them because they damage river flows, stream flows and create highly flammable landscapes.

"It's not lost on Chileans and people from the Mediterranean, from Portugal and Spain, how dangerous eucalyptus plantations are."

Professor Bowman believes a return to traditional land management practices is inevitable.

"What's happened in Greece really highlights that things are really out of whack now. So a bigger issue, not just about Australia, is looking at cultural systems that work."

Topics: environmental-impact, environmental-management, indigenous-culture, drought, rural, nundle-2340, currabubula-2342, tamworth-2340, denman-2328, coonabarabran-2357, pooncarie-2648, menindee-2879, avoca-2577, aramac-4726, merriwa-2329, cassilis-2329, broken-hill-2880, orange-2800, bega-2550, port-macquarie-2444, coffs-harbour-2450, armidale-2350, wagga-wagga-2650, dubbo-2830, sydney-2000, university-of-western-sydney-2560, mount-isa-4825, toowoomba-4350, coober-pedy-5723, cleve-5640