5 minute read
Rescuing Gondwanan rainforests
WORKING WITH INDIGENOUS COMMUNITIES AND LAND CARE GROUPS, SCIENTISTS ARE EXPLORING WAYS TO PRODUCE RESILIENT POPULATIONS OF RARE RAINFOREST PLANTS, ENSURING THEY SURVIVE AND THRIVE. BRETT SUMMERELL REPORTS.
The Gondwanan rainforests of northern New South Wales and southern Queensland are one of the most unique set of ecosystems in Australia. Sadly they are also one of the most threatened. It is estimated that just 1% of these rainforests remain – the rest largely lost to the logging and land clearing associated with the expansion of agriculture in these regions over the past 200 years.
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These rainforests, which are found between Newcastle and Brisbane, are termed Gondwanan because when Gondwana existed (from 500 million years ago until it started to break up between 180-100 million years ago) it was, according to fossil records, covered by rainforests containing similar kinds of species that are living in these locations today. As a result, these rainforests have been designated World Heritage areas, and much of the existing rainforest has been protected in national parks.
These ecosystems have long been a focus of interest to the Gardens and its scientists. If you wander round the Royal Botanic Garden Sydney, you will notice that many of the mature trees come from these ecosystems and previous directors such as Charles Moore and Joseph Maiden were particularly fond of planting species from these regions. More recently our focus has turned to rescuing at-risk species and enhancing the restoration and rehabilitation of these forests in northern NSW.
Apart from the long-term impact of logging and land-clearing, these forests now face a number of new threats. In the Black Summer fires in 2019/20 we saw quite extensive impacts on these ecosystems – rainforests, as the name implies, are not expected to burn, not adapted to bushfire, and when they do burn it takes years, even decades for many of the species to recover.
Additionally, many of the rainforest species in the family Myrtaceae are very susceptible to the exotic fungal disease Myrtle Rust. The combination of warm, wet weather and very susceptible species has seen this disease proliferate to the point where there are an estimated 16 species of rainforest Myrtaceae at imminent threat of extinction from the disease.
In order to address these issues sustainably we need to find answers to a number of complex challenges – including how to collect, store and generate seed and other germplasm and how best to produce resilient populations of plants that will not only survive but will produce the next generations of plants.
Our current areas of focus with respect to Gondwanan rainforests are centred on understanding the genetic resilience of the species in these forests – a critical factor given the shrinkage of these populations as outlined above – and on determining better ways to collect and store the seed of rainforest species. This latter factor is important as it may provide an opportunity to preserve at-risk populations of species and to extend the life of seed, which for many rainforest species can only be used freshly picked.
Many of the plant species in these forests are of great cultural significance to Indigenous people. Species like Black Bean (Castanospermum australe) and the Bunya Pine (Araucaria bidwillii) were important food sources and, where the trees were located at some density, sites of congregation and celebration. Given this, it is not surprising that efforts were made to cultivate these trees, and Professor Maurizio Rossetto from our team at the Research Centre for Ecosystem Resilience – working with PhD student
Black Bean pods and seeds
Professor Maurizio Rossetto examines Black Bean seeds Large Black Bean seeds
Monica Fahey, Dr Emilie Ens from Macquarie University and members of local Aboriginal communities – is currently investigating the history and biogeography of these species using genomic tools. The focus is on exploring the relationships between trees and documenting how the trees might have been moved around the landscape.
The Black Bean tree, for example, is a culturally important riparian (growing near a river) tree that produces toxic but highly nutritious water-dispersed seed known to have been detoxified and consumed by rainforest dwellers in the Australian wet tropics for at least 2,500 years. The genomic study showed unusually low genetic diversity among the many populations that grow from the coast to the uplands (often away from natural water courses) and that they were derived from a single maternal lineage. Based on ecological and environmental information, Professor Rossetto could rule out dispersal by natural factors such as rivers, rainforest birds and mammals, and identify movement by local Indigenous people as the most plausible alternative. The tree’s journey through NSW, as told by its genetics, is compatible with the traditional Dreaming Tracks that local Aboriginal people have travelled for thousands of years. These are related within traditional songlines and stories that support traditional knowledge sharing.
The other component of our work in these ecosystems is collaborative work with local community groups such as the Big Scrub Landcare organisation to develop innovative methods for restoration and community involvement in propagating and spreading at-risk rainforest species.
A combination of genetic information and propagation technology – whether it is seed storage and germination or cutting propagation – provides the opportunity to produce resilient restored patches of bush. It also provides us with the opportunity to create seed production areas that will comprise genetically diverse individual plants. These plants will cover the full spectrum of diversity that can interbreed in order to produce seed for use in restoration, creating resilient populations capable of producing offspring that can cope with all the negative impacts thrown at them.
Much of this work has been supported by a range of donations and grants over recent years and these have now been bolstered by fantastic support from the Minderoo Foundation’s Fire and Flood Resilience program over the next few years. This support will enable us to expand our influence and help to protect more rainforest species.
