For many thousands of years, certain plants have evolved to tolerate and actually encourage fire. Pyrophytic plants, such as Australian Eucalypts, don’t merely withstand fast-moving blazes, but they require them for their survival, as their cones release seeds after the fire’s heat melts their resin. In other words, to resprout, fire is the essential ingredient for healthy pyrophytic plants.
Highly flammable eucalyptus oil sits in the trees’ crowns and remains in the fallen leaves. The bark and branches that seasonally fall to the ground combine with the oil to create the perfect tinder, which decimates native habitats. And the eucalyptus continues its process of growth and regrowth amongst the destruction, sprouting fire-germinated seeds that rise from the ashes.
Eucalyptus is loved widely for its beautiful aroma, its medicinal properties, and for offering food and shelter to koalas, who feed ingeniously on the tree. But recent events could threaten how we perceive eucalyptus. The heartbreaking 2019-20 Australian bushfires—a catastrophe that immolated 18.6 million hectares—brought the eucalyptus tree’s future into serious question.
Just as the catastrophic bushfires raise important questions for eucalyptus, so too do they raise important questions for us. How will Australia have to change as it grapples with wildfires and the climate crisis? Is there a better way to farm this plant that won’t rely on such volatile conditions?
Down Under Enterprises grows, produces, exports, and markets traceable and sustainable native Australian essential oils and botanicals. They farm eucalyptus using a conventional ‘organic in conversion’ method, extracting it through steam distillation. Produced from eucalyptus kochii trees indigenous to Western Australia, their oil is pure and unfractionated.
Unlike monoculture farming, the eucalyptus kochii trees grow in harmony with other crops to maintain a healthy ecosystem. Eucalyptus defines the Australian landscape and its history. But this isn’t so in foreign ecosystems, where it becomes a risk to the soil, local wildlife, and water supply—which Phillip Prather, the Head of Operations at Down Under Enterprises, says was the case with the devastating blazes in California.
“When eucalyptus hits a different environment, it essentially becomes a noxious weed,” Prather says.
Prather explains that eucalypts have a protective mechanism that enables them to react to fire and stimulates epicormic growth. (This latter process occurs when buds that sit beneath the bark resprout after crown damage.) Other trees don’t have this protective mechanism, and it’s this adaptive survival function that negates competition from other trees such as pines.
“We’ve seen the epicormic growth in eucalyptus plantations since the recent bushfires, whereas the pine that was planted had to be cut down and started all over again,” Prather adds.
One of the most popular tree types that produces oil, eucalyptus radiata, was decimated during the Australian bushfires. This will require replanting to bring stocks back. While eucalyptus can handle a quickly passing flash fire, the recent bushfires were so hot, trees were burned all the way through.
“Even eucalyptus didn’t survive the intensity of those fires.”
Prather and his team only use fire in the production of their essential oils to create their distilling steam.
“Fire is going to burn the leaves and that’s what we need to produce essential oils. We don’t use fire to refresh the trees and we do our best to avoid putting carbon into the atmosphere. What we rely on is cop-picked growth.
“Our trees are propagated from seeds to produce seedlings, which are planted and ready for cutting within two to three years. Eucalyptus is really good at tapping the groundwater. An arborist we work with, Dan Wildy, found the taproots go down 26 meters. Eucalyptus is amazing at tapping the water table.”
During the 1990s, the Western Australian coastal wheat belt was decimated after farmers deforested the area. This caused the water table to rise. The ocean air carried salts which filtered down into the depths of the water table. When the table started rising, the salt came with it, drastically increasing the salinity of the environment.
“The other part of Dan Wildy’s research was to look at what happens to tap and surface roots when you cut the tree and encourage the cop-picked growth. The plant has an adaptive response and it sheds its surface roots and it starts drawing water back deep again,” Prather adds.
“Now, we work with farmers to coppicing-cut all trees, encouraging the tap roots downwards and preventing the surface from taking the moisture.”
As for the daily use of fire in essential oil production, Prather says it doesn’t work in the lifecycle, but it is sometimes leveraged in fuelling the biomass.
“After the trees are cut down, they get shredded, going into a holding bin. We put steam into the bin that goes up through leaves and out through the top port. The oil from sacks in the leaves that the steam has exhumed then condenses back into liquid when the temperature is reduced. The oil sits on the top and the water on the bottom.”
“Once the leftover leaf matter dries out, it can be used to fire the boiler to produce steam for additional oil production. The biomass can also be put back into compost mixture and spread out across the fields as organic fertilizer.”
Australia is one of the most biodiverse places on earth. Ancient and adaptable, the eucalyptus trees are a fascinating part of the Australian landscape. Down Under Enterprises offers an encouraging example of how farmers are adopting new strategies for this historic plant.
But this is just one example.
One researcher is imagining a fascinating future for eucalyptus—turning Australia’s gum leaves into low-carbon, renewable jet engine fuel. According to Carsten Kulheim, who works at the Australian National University, eucalyptus oil is rich in compounds stronger than those found in ethanol fuels. The compound, monoterpenes, can be converted into a very high energy fuel.
Kulheim and his co-researcher, David Kainer, believe Eucalypts are capable of producing five percent of the world’s demand for energy, with minimal ecological impact. While the current literature is light, using eucalyptus plantations to support renewable fuels is an exciting prospect.
Eucalyptus trees are ancient, intelligent, and somewhat mystical to those who learn their characteristics. The fire-adaptive trait might be just one aspect of their iterative life.
The future of this pyrophytic species is up for grabs. As much as anything, the eucalypts face an existential dilemma much like our own: How to survive the climate crisis without exacerbating its effects, and how to live when the system that sustains it may also decimate it.