An Australian sheep farmer (we would say “rancher”), Jane Pye, spotted our defense of eucalyptus and got in touch:
“G’day, I stumbled across the SFFA website researching ‘allelopathy’ in eucalypts and was amazed to find so much antipathy towards gum trees over there – like an arboreal cane toad! What I really wanted to know is do you have any evidence of ‘positive allelopathy’ re eucalypts? I live in the Australian outback with areas of dry sclerophyll forest. The commonest eucalypt here (Eucalyptus populnea) is often surrounded by native scrub trees & bushes. Strangely some of these box trees also have other trees growing out of their trunks which I think were planted there by the traditional owners (Aboriginal). These Tree in Trees are found in clusters around the old indigenous campsites, which are in turn found around good natural water catchments or native wells.”
My article debunking the popular myth that eucalyptus is allelopathic was republished by the San Francisco Forest Alliance (SFFA). The myth of allelopathy is that eucalyptus emits a chemical that prevents the germination of other species, eliminating competition with eucalyptus for resources such as water. But Jane’s experience with eucalyptus goes beyond debunking allelopathy in eucalyptus. She has documented many examples of different tree species that have seemingly been planted inside the cavities of eucalyptus trees. The eucalypts are a sheltering host to the guest tree species. Clearly, eucalyptus is not inhospitable to other plant species.
Jane believes that these “trees in trees” were intentionally planted by indigenous Aboriginal “farmers.” She believes that this is one of many techniques that were developed by Aboriginal people to manage the land and vegetation to provide food and cultural implements. She explains on her website:
“After years of admiring and speculating about these scar trees, I have finally gotten around to photographing most of them. I spend many days in the paddocks mustering sheep and some of these trees are like old friends. They are an important link to our Aboriginal past and a reflection on how innovative and resilient these people were. Surviving out here west of Walgett with our unpredictable climate of harsh droughts and random floods is still tough but these people managed their environment and thrived.
“So I dedicate this website to Freddie Walford, an Aboriginal stockman we had who taught us some bush lore and like many of his people, died too young. I will always remember his natural affinity with livestock, his love of polocrosse and his quiet humour and grace. He never spoke much about the scar trees but did say if I was ever to see bones inside an old coolabah [Eucalyptus coolabah], I should go as fast as possible in the opposite direction! This website aims to increase knowledge and record these trees but not to display any pictures or information that is culturally secret or sacred.”
The land management practices of Australian Aborigines were very similar to those of indigenous Californians for much the same reason. These were hunter-gatherer cultures living in similar climates with seasonal drought. They moved around as seasons changed and their diets changed accordingly. Both cultures used fire as one of their primary tools. Periodic fires refreshed the grasses that fed the grazing animals they hunted. The primary grazers in Australia were kangaroos and other marsupials; deer and other ungulates are the original grazers in California.
The land management practices of indigenous people are enjoying a renaissance. A recent study of Aboriginal land management in Australia said, “Indigenous agency and governance is driving innovations in land management worldwide that provide more equitable solutions and strategic approaches to looking after the lands, waters and all living things, particularly in the face of climate change.”
Such intentional burns are now seen as a way to keep the brushy fuels that carry fire to a minimum, reducing wildfire hazards. Cal Fire’s new “Wildfire and Forest Resilience Plan” and the Governor’s recent annual budget proposal tell us that more prescribed burns are planned in California to reduce fuel loads and fire hazards: “CAL FIRE will expand its fuels reduction and prescribed fire programs to treat up to 100,000 acres by 2025, and the California Department of Parks and Recreation and other state agencies will also increase the use of prescribed fire on high risk state lands.”
It has taken hundreds of years to appreciate the value of indigenous land management and its context in their culture. When Europeans arrived in both America and Australia, settlers assumed that their culture was superior to indigenous culture. Early settlers made no attempt to learn from indigenous people, which was the settler’s loss. Indigenous people had learned to live off the land, in most cases without cultivating crops and without domesticated animals. Rather, indigenous people learned what was edible and what had medicinal value. The first European settlement in America, Jamestown, ended quickly with starvation, because the settlers weren’t able to understand what the land offered them. In Australia, knowledge of indigenous land management was also delayed by the cultural taboos of the indigenous people that prohibited the revelation of many of their cultural practices outside their ancestral clans.
Wildfire in Australia
Jane also had some interesting observations about wildfires in Australia that are consistent with our experience in California:
“I’m sorry to hear eucalypt forests are being destroyed over there as they are wonderfully useful trees. We don’t have many fires in inland Australia. It’s more of a coastal / high rainfall problem. We just don’t get the fuel build up as it’s a semi-arid region and we have thousands of merino sheep eating the grass and shrubs. There have been no fires on this property in over a century and probably much longer. We also have efficient native grazers – kangaroos and wallabies and now also goats that are increasingly common as an alternative to sheep.”
This is the strategy that I promote on this website. If we reduce ground fuels that ignite easily, we can prevent most fires from igniting tree canopies that are harder to ignite. Fire travels fast on the ground if given a continuous field of dry grass during the dry season. Grazing animals are a far safer way of reducing these grassy ground fuels than the herbicides that are often used. Herbicides leave a dead, dry thatch on the ground that is very flammable and grazing does not.
“Also we are very used to fire over here and many people regard those foolish enough to build in fire prone areas have only themselves to blame. Some of our small coastal towns are totally surrounded by National park and State forest and only have one road in – that’s why there were so many images of people sheltering on beaches last summer. It’s a hard issue but better hazard reduction burns and more fire fighting aircraft seem to be the way forward here. Also better fire retardant building materials.”
These observations are also consistent with the strategy that makes sense to me. We must learn to live with fire because it is an essential element in Mediterranean ecosystems. We can’t prevent it, but we can work around it with zoning that prevents building in extremely hazardous areas, using fire retardant building materials, and creating safe evacuation routes.
Alerted by Jane, I noticed this woody shrub sprouting from a eucalyptus stump in Stern Grove a few days after I heard from Jane. Clearly, eucalyptus does not retard the growth of other species.
Many thanks to Jane for getting in touch with us. Thanks for her admiration of eucalyptus and Aboriginal culture. I’ve had some lovely email chats with Jane. Perhaps you would like to drop her a line to thank her as well: email@example.com