How can you save what you cannot name, what you do not know? A broad new report on plants and fungi highlights 'knowledge gaps', issuing yet another call to preserve biological diversity.

More than 75% of the planet’s 'undescribed' plant species are already at risk of extinction, according to the latest report prepared by Kew Gardens (UK).

All newly discovered species must be officially named and described. New plants and fungi are found every year. However, the double crisis caused by biodiversity loss and climate change means that valuable organisms are disappearing before our eyes. The fifth edition of the 'State of the World’s Plants and Fungi' report, published by Kew Gardens on 10 October, summarises all the latest research. The compilation highlights significant gaps in our knowledge of plants and fungi.

'At a time when plants and fungi are increasingly under threat, we must act quickly to close knowledge gaps and set conservation priorities,' says Professor Alexandre Antonelli, Director of Science at the Kew Gardens Royal Botanic Gardens.

Below are some of the key findings from the report. They are based on the work of more than 200 researchers and 25 of the latest scientific studies. Nature continues to surprise us. For example, researchers in Brazil have found a tree that was thought to have been extinct for nearly 200 years.

Describing new plant and fungal species is crucial for their protection

Last year at COP15, countries agreed to reduce the rate of species extinction in line with the Global Biodiversity Framework. Experts still find it difficult to answer a seemingly simple question: how many plant and fungal species are there in the world? Two significant achievements will help scientists refine the answer.

Firstly, Belgian botanist Rafaël Govaerts, who leads the Plant and Fungal Names classification group at Kew Gardens, has created The World Checklist of Vascular Plants (WCVP) after 35 years of research. 'More than 160 years ago, Charles Darwin dreamed of a complete and accurate list of the world's plant species,' says R. Govaerts. 'Creating such a list was also my dream, spurred on by the rapid decline of tropical forests and biodiversity that I witnessed as a student in the 1980s. I am delighted to see that the idea of creating the list is finally being realised.'

Secondly, environmental DNA analysis of soil samples from around the world has provided a wealth of new information about fungal diversity.

Scientists estimate there are 2.5 million fungal species on Earth

90% of the so-called 'fungal kingdom' remains a mystery to scientists...

To date, only 155,000 fungal species have been officially named. Researchers have long suspected that the 'fungal kingdom' is as diverse as, if not more diverse than, the plant and animal kingdoms. Previous estimates ranged from 250,000 to 19 million fungal species. Now, partly thanks to technological advances such as DNA metabarcoding, scientists estimate that there are approximately 2.5 million fungal species in the world, meaning more than 90% of fungal species are still unknown to science. Only 0.02% of them have been assessed for global extinction risk.

'Naming and describing species is an essential first step in documenting life on Earth,' emphasises Dr Tuula Niskanen of the University of Helsinki. By knowing a species, researchers can share information and assess its conservation status to understand if it is at risk of extinction, etc. Scientists can then study its potential benefits. Plants and fungi are the foundation of life on Earth, providing valuable ecosystem services. They are our livelihood and food, providing us with medicines, clothing, and raw materials.

So far, only about 10% of the world's fungal biodiversity has been described. Humanity could lose valuable species, such as those whose enzymes are capable of breaking down plastic. 'It is important to know what fungal species we have (on Earth) and what needs to be done so that we do not lose them,' adds T. Niskanen.

Three out of four previously unknown vascular plants are at risk of extinction

Science already knows about 350,000 species of vascular plants – plants that have specific tissues for conducting water and nutrients to their structures. Most plant species fall into this category, ranging from flowering plants to seed plants such as conifers and ferns. The problem is – up to 100,000 of these species have not yet been officially named. New estimates suggest that three out of four undescribed vascular plants are likely already threatened and at risk of extinction. This figure was derived by scientists analysing WCVP and IUCN Red List of Threatened Species data to identify the link between the year a plant species is officially described and its risk of extinction. A clear link was found: more than 77% of species described in 2020 met the criteria to be assessed as threatened. Species described recently are more likely to meet the criteria for a higher category of threat.

Nearly half of all flowering plant species could go extinct

Looking at flowering plants, researchers claim that 45% of all known species could be at risk of extinction. Orchids are the most threatened. Extinction also threatens the Bromeliaceae plant family, which includes pineapples, the Piperaceae family, which includes black pepper, and the Araceae family, which includes many important food crops.

A plant known as the 'waterfall orchid' is an example of how plant existence is threatened (the plant is not from the Orchidaceae family, but from a group that grows near waterfalls and rapids). The plant Saxicollela deniseae was discovered in 2018 along the Konkouré River in Guinea by botanist Denis Molmou. Four years later, in May 2022, the description of the species was officially published. Satellite images taken as early as November 2021 showed that the waterfalls where the species was found had been flooded. The reason was the construction of a hydroelectric power station 30 km downstream. Scientists believe that Denis Molmou was the first and most likely the last person ever to see this species in the wild.

'Personally, I have observed that the number of threatened plants has increased shockingly in recent years,' emphasises Dr Martin Cheek, Senior Research Leader in the Accelerated Taxonomy department at Kew Gardens. 'When I started working as a taxonomist 30 years ago, I could not have imagined that a species being published could go extinct shortly after. It was easier to assume it would still be found in the wild.'

Should new species be considered threatened until proven otherwise?

Based on the findings mentioned above, Kew Gardens scientists say 'yes'. They are calling for all newly described species to be treated as though they have been assessed as threatened, unless proven otherwise. Unfortunately, an increasing number of newly described species have a narrow range (many are described from only one site) and are experiencing population and/or habitat loss.

'If our recommendation is adopted, it could help protect many tens of thousands of undescribed species. They should be considered threatened as soon as they become known to us,' points out Dr Matilda Brown, a researcher in the Conservation Assessment and Analysis department at Kew Gardens.

Scientists believe that these species must be prioritised for full assessment on the IUCN Red List. As a result, they will have a better chance of survival. At the same time, Kew Gardens scientists are striving to shed light on the planet's 'dark spots of biodiversity' – areas where data on plant diversity and distribution is lacking. Of the 32 identified locations, at least 44% are in the tropical regions of Asia. This clearly shows where field research needs to continue.
https://www.euronews.com/green/2023/10/10/over-75-of-earths-undescribed-plants-threatened-by-extinction-new-report-warns