A race against time is underway to save a unique rainforest tree species, Rhodamnia zombi, from becoming a true 'zombie tree' and disappearing forever. This species, identified just as it began its potential demise, is facing a deadly fungal disease known as myrtle rust. The disease infects new growth, preventing the tree from maturing and reproducing naturally in the wild. Field surveys revealed a dire situation, with some trees already lost and none of the remaining population producing flowers or fruit.
The disease's impact is profound. It arrived in Australia from overseas in 2010 and has since spread rapidly through native forests. Professor Rod Fensham, a botanist at the University of Queensland, describes it as a race against time. He emphasizes the tree's dire situation: "If you can't grow or reproduce, your chances of survival are slim."
Rhodamnia zombi, found in Queensland's Burnett region rainforests, is characterized by its large dark green leaves, shaggy bark, and hairy white flowers. Professor Fensham notes, "It's a challenging situation across its range. If the tree can't build up energy reserves, it eventually gives up. And without the ability to produce seed, the next generation has no hope either."
Myrtle rust has proven to be a formidable foe, with many native plants struggling to tolerate it. Rhodamnia zombi is one of 17 species classified as facing extinction due to this disease. Professor Fensham warns that without intervention, these species could disappear within decades. He reflects on the profound nature of such a loss: "For something that has evolved over millions of years to vanish within a generation is a tragedy. It's a stench, but also an extraordinary phenomenon to witness."
The path to survival for Rhodamnia zombi lies in resistance. Some close relatives of the species show natural tolerance to myrtle rust, giving scientists hope that resistance genes may be present in the genome. However, Professor Fensham highlights the challenge: "The problem is that this evolutionary process cannot occur in the wild because the trees are no longer producing seed."
To combat this, scientists have partnered with specialist nurseries to grow clean cuttings in protected conditions. The goal is to keep the plants disease-free long enough for them to flower and produce seed, allowing the next generation to be tested for tolerance. Professor Fensham describes it as a rare opportunity to witness evolution in real time.
On Queensland's Sunshine Coast, Barung Landcare is one of the groups leading the charge to keep Rhodamnia zombi alive. Horticulturist Alexandra Hayes-Hatten and conservation trainee Milo Wakeman-Bateman collect cuttings from wild populations and propagate them in controlled environments. In the nursery, the shoots are carefully trimmed, treated with rooting hormone, and monitored for any signs of infection.
"It's a delicate balance," says Ms. Hayes-Hatten, "but some are doing remarkably well." For her, the work is both daunting and inspiring. "Learning about a species that could potentially become extinct in an instant is scary. But we have the people and resources, so we must step up and take action."
Nursery specialists in Lismore and Townsville have also joined the rescue efforts. The long-term hope is to identify resistant individuals and reintroduce them to the forests where Rhodamnia zombi once thrived.
Professor Fensham acknowledges the ambitious nature of this goal: "These trees need time and space away from constant exposure to myrtle rust to express any resistance. Left alone, Rhodamnia zombi will remain what we've named it—living dead."
The battle to save Rhodamnia zombi is a testament to the dedication of scientists and conservationists, who are working tirelessly to prevent the loss of this unique species and ensure its survival for future generations.
