A nationwide study published earlier this year, examined 2.5 million Australian herbaria specimens. It found that 47 per cent of the country’s native vegetation is potentially at risk from rising temperatures by 2070.
Some plant die-back on Sydney's Middle Head is caused by phytophthora, which thrives in warmer conditions.
Phytophthora is a soil-borne water mould that causes enormous economic losses to crops and natural ecosystems worldwide.
“There is a pattern of plant die-back across the country, and it’s caused by things like phytophthora and other pests and pathogens,” he said.
“And it’s becoming very serious everywhere we look.”
Dr Summerell holds a PhD from the University of Sydney and has published extensively on plant pathogens. He said it's vital the country's species are protected.
“The smell of a gum leaf or a banksia or waratah flowering, these are strong aspects of our culture, so it’s incumbent on us to preserve and save our species,” he said.
In the nationwide study 'Safety margins and adaptive capacity of vegetation to climate change', published in June in Scientific Reports, Dr Rachael Gallagher from Sydney's Macquarie University found many species are already struggling in warmer temperatures.
“Our study identified 151 species that are already at their upper limit for warming, and further rises present a considerable challenge for those species,” she said.
“This is the first time we’ve had a contintental-scale analysis like this of Australia’s vegetation, and its risks under climate change.”
Climate modeling predicts a rise of between two and four degrees in Australia’s mean annual temperature over the next 50 years, she said.
“The rate of climate change is so much faster than we have experienced in the past, it’s a very rapid transition to a very warm environment.”
“As a result of changing climate we run the risk of losing species that we don’t even know exist at this time,” she added.
Species flowering earlier
Scientists studying flowering patterns found many species are also flowering earlier when compared with historic specimens.
Firefighters are also battling an early and destructive bushfire season, after one of the warmest and driest winters on record. Severe fires are already impacting south-east Queensland and NSW.
“When bushfires occur out of ordinary range, only some plants survive,” Dr Summerell said.
If fires occur in early spring, plants are thrown out of cycle for flowering and setting seed, he said.
Plants growing tropical areas and alpine regions are particularly susceptible to climate change.
“Feldmark grass Rytidosperma pumilum is extremely vulnerable, as it only grows in a three square kilometre area in the high alpine section of Kosciuszko National Park,” Dr Summerell said.
“We expect is that once temperatures rise, woodland will overtake this area and feldmark grass will become critically endangered and move towards extinction.”
“Retaining a rich diversity of plants is not only important for the environment. We also rely on plants for food, water, medicine and the air we breathe.”
Breeding resilient species
At the National Herbarium of NSW, scientists are photographing more than 1.4 million specimens, to create an online data bank.
“It’s an amazingly powerful resource,” Dr Summerell said.
Information about plant specimens, collected over 250 years, will be analysed to reveal flowering patterns and enable scientists to examine cellular structures.
Scientists are also sampling DNA to help breed more resilient species, used to restore mine sites or degraded farmland. Threatened species may also be migrated to cooler sites.
Some of the oldest surviving samples were collected from Botany Bay by early explorer and naturalist Joseph Banks on James Cook’s first voyage to Australia on HMS Endeavour in 1770.
The specimens are lucky to have survived. Banks retrieved his collection from the sea after the Endeavour ran aground on the Great Barrier Reef, Dr Summerell explained. Samples were dried out on the sails of the ship, and taken to Britain. The specimens were later returned to Australia.
The digitising work is expected to continue until 2021.
Dr Summerell said it will form a valuable and accessible resource for scientists studying the impacts of rising temperatures on plants worldwide.
Scientists say preserving species diversity is crucial for healthy bush and cultivated land. Farms need paddock trees and areas of native vegetation as habitat for native birds and mammals.
"And there are other benefits of keeping trees: they lower the water table and provide shade for stock. So keeping a mix of flora can have important flow-on benefits for species protection and crop or grazing land,” Dr Gallagher added.
People can report die-back to The Dead Tree Detective, a project at Western Sydney University.
Nurseries advise gardeners to plant hardy, drought-tolerant species, with water restrictions active in some states.
"More people are asking for native plants so we're selling a lot of grass trees, grevilleas, and beautiful flowering gums," Jack Thorburn from Sydney nursery Honeysuckle Garden said.
"We also advise people to treat the soil with a wetting agent and mulch often."
Dr Gallagher called for urgent action to protect Australian flora, in particular endemic plant species that occur nowhere else in the world.