Stuart Worboys (Laboratory & Technical Support Officer, Australian Tropical Herbarium), Darren Crayn (Director, Australian Tropical Herbarium), Warren Worboys (Curator, Horticulture, Royal Botanic Gardens Cranbourne) and Karen Sommerville (Research Scientist, The Australian PlantBank, Royal Botanic Gardens and Domain Trust)

Queensland’s Wet Tropics conserve one of Australia’s most biologically diverse ecosystems. With its high mountains, fire-free rainforest landscapes, geological diversity and a warm humid climate that has remained stable over geological time, the bioregion preserves a biota that is recognised internationally as representing a living record of major stages in the earth’s evolutionary history.

The Wet Tropics World Heritage Area conserves a significant proportion of the bioregion’s flora and fauna in an area of roughly 900,000 ha. Although not the largest tropical rainforest, nor the most diverse, it is among the most irreplaceable. It has been ranked eighth out of more than 173,000 protected areas worldwide for irreplaceability based on its extraordinary total species diversity, and sixth on the basis of globally threatened species alone. Of World Heritage properties listed for their natural values, it is ranked the second most irreplaceable site globally. Yet although these protected areas are secure, anthropogenic climate change will significantly impact their living inhabitants.

The effects of climate change on fauna has already been documented, with some endemic birds and mammals disappearing from mid altitude forests, and becoming restricted to higher altitude locations. However, the impacts on the bioregion’s endemic mountain flora had received little consideration until a 2015 study by researchers at the Australian Tropical Herbarium. This study predicted a significant decline, or complete wipe-out of available habitat for 19 vascular plant species. This concerning outcome prompted action: firstly, an expert meeting was convened to develop a comprehensive listing of bioregionally endemic mountain flora species; secondly, expeditions were organised to acquire detailed and accurate information on the distribution of these species; and thirdly, a pilot conservation program was established to document, collect and propagate two of the target species – Australia’s only native rhododendrons.

From the outset, this project was a collaborative exercise. Grants from the Ian Potter Foundation and the Australian Rhododendron Society facilitated the involvement of Traditional Owners and land managers, and allowed helicopter access to remote sites. The initial survey expeditions undertaken in 2016 and 2017 collected over 800 target species records from the Wet Tropics’ highest peaks, with just one medevac from hundreds of person hours in remote, rough terrain. The involvement of outside expertise in these trips led to unexpected outcomes, including finding ferns never before seen in Australia, moss species entirely new to science, a presumed extinct fern and a possible new tree species.

We are now in the second phase of the project, thanks to a major grant from the Ian Potter Foundation which has enabled the expansion of the project’s scope. The project’s goal is to “secure the future of Australia’s climate-threatened tropical mountaintop plants… by building a multi-strategy ex-situ conservation reserve to ‘backup’ at-risk wild populations and support research, display and education.” With the involvement of horticultural expertise from the Australian Rhododendron Society, the Australian National Botanic Gardens, the Royal Botanic Gardens Victoria and the Royal Botanic Gardens and Domain Trust, Sydney, we now have 40 of the roughly 86 target species of vascular plants in cultivation. Most of these plants have never previously been grown in cultivation and required development of novel methods of propagation through much trial and error.

All cultivated plants are represented by vouchers held in herbaria, and genetic samples are taken from each population. The provenance of all plants is carefully documented, and propagated plants will ultimately be distributed to participating botanic gardens up and down the east coast of Australia. Public education and outreach is an intrinsic part of the project, with signage being developed for the botanic gardens plantings, and an artist-in-residence, Donna Davis, developing and exhibiting work centred on the project.

Seed banking is another potential option for plant conservation, but little is known about which species in this habitat have seeds that are sufficiently tolerant of desiccation and freezing to enable long-term storage. The Ian Potter grant is facilitating research into seed storage behaviour for these species at the Australian PlantBank in Sydney and the National Seed Bank in Canberra. Research into the effect of changing temperatures and light quality on germination of the seeds is also being conducted and will serve to better inform future models of the impact of climate change.

Although a few of the target plant species are restricted to just one mountain, most occur on multiple peaks. We have considered these populations to be reproductively isolated, and therefore genetically unique. But to ensure that this assumption is correct, and that genetic diversity is maximised within the ex-situ conservation plantings, funding has been secured to generate genomic data for 14 of the target species. The results of genetic analysis will inform selection of genotypes for ex-situ cultivation, and prioritisation of populations and sites for future field collecting work.

None of this work would be possible without partnerships with land managers, and we are pleased to be working with the Wet Tropics Management Authority, the Queensland Parks and Wildlife Service and Western Yalanji First Nations people.