Australia has the world's highest proportion of unique plants but is doing a poor job of working out if they're in danger, a global assessment has found.
Conservation experts have gathered in London to provide a snapshot of plant heath and what countries are doing to safeguard hundreds of thousands of species.
It warns an estimated 45 per cent of the world's known flowering plants could be at risk of extinction as climate change and other threats mount.
The situation is even worse for 100,000 or so plant species yet to be formally named, with an estimated 75 per cent of those at risk of vanishing.
The study analyses what individual nations are doing to protect their unique species - those found nowhere else on earth. In Australia, almost nine out of 10 plant species fit that bill.
But the nation isn't doing what's needed to understand if they are in trouble.
"By international standards, Australia performed very poorly in conservation assessments," said Western Sydney University's Rachael Gallagher, who led the global evaluation of those efforts.
Only 39 per cent of Australia's unique species have had their threats and conservation status assessed - less than half of what New Zealand and South Africa have managed.
Australia's efforts were more on par with low-income countries such as Madagascar, on 42 per cent.
"Without comprehensive assessment thousands of unique Australian plant and fungi species could be at risk, and we have no way of knowing which species or where to direct conservation efforts," Associate Professor Gallagher said.
NSW's floral emblem, the waratah, is a perfect example. Its extinction risk has never been assessed even though it is targeted by illegal flower collectors, and threatened by climate change and altered fire regimes.
Australia is also home to about 1000 of the world's 1350 acacia, or wattle, species. But there's been no threat assessment for almost half of those 1000.
University of Queensland Professor Hugh Possingham also worked on the assessment and said it's time for Australia to lift its game.
"More than half of the world's plants - 221,399 species - occur in only one country. The countries that are custodians of these unique species have a responsibility to assess if they are at risk and take steps to conserve them if they are."
The global assessment also identified 32 dark spots - places where data is so lacking that scientists are in the dark about their biodiversity. Western Australia and Queensland are among them.
"Knowing where there are most species remaining unnamed and unmapped, of which many are likely to be threatened, is crucial ..." said Dr Samuel Pironon, who works with the UN Environment Programme World Conservation Monitoring Centre.
"Understanding where the unknowns are concentrated could also help us refine our estimates of priority areas for conservation."
The State of the World's Plants and Fungi 2023 report from the Royal Botanic Gardens Kew is based on the work of 200 international researchers who have drawn from 25 major scientific papers.
