In the first ever report looking into the world’s plants and their status, scientists have cataloged almost 400,000 known species. The inaugural report on the State of the World’s Plants covers all vascular plants, which includes those that flower along with conifers and ferns, and shows that despite the vital role they play in all of our lives on a daily basis, one out of five species is currently threatened with extinction, with threats ranging from climate change, to invasive species, to disease. 
“This is the first ever global assessment on the state of the world’s plants,” explains Professor Kathy Willis, Director of Science at the Royal Botanic Gardens, Kew, who compiled the report. “We already have a ‘State of the World’s… birds, sea turtles, forests, cities, mothers, fathers, children, even antibiotics, but not plants. I find this remarkable given the importance of plants to all of our lives – from food, medicines, clothing, building materials and biofuels, to climate regulation. This report therefore provides the first step in filling this critical knowledge gap.”
The report looks only at what are known as “vascular” plants. The majority of people will know these from most of the plants that you can currently see around you, as they include all flowering plants and trees, conifers, and ferns, but miss out algae, moss, and liverworts. The researchers found that despite there being over one million named species, each plant actually has on average 2.7 names, as many species have been named and described more than once by accident.
Taking all this into account, the researchers came to their final conclusion that there are roughly 390,900 plants known to science, of which approximately 369,400 are flowering. Yet that, according to Professor Willis, is “just scratching the surface.” Last year, for example, over 2,000 new species were described, ranging from tiny orchids known only from traders to a towering tree that reaches 45 meters (150 feet) and weighs in excess of 100 tonnes (110 tons) found in the tropical forests of Gabon.
One of 90 new species of Bergonia, in this case Begonia ruthiae, described last year from the forests of South East Asia. Julia Anak Sang/Kew
“But there are still large parts of the world where very little is known about plants. Identification of these important plant areas is now critical,” said Steve Bachman, strategic output leader for the new State of the World´s Plants report. “Similarly, we still only know a fraction of the genetic diversity of plants and whole-genome sequences are currently available for just 139 species of vascular plants. Activity in this area needs to speed up.”
The discovery that 21 percent of all known plants are at risk of extinction should also ring alarm bells, the researchers write. People rely on over 30,000 different species of plant for medicine, food, and materials to name a few, and with increasing importance put upon safeguarding the wild relatives of common domestic species, more effort should be put into filling the gaps in our knowledge in this area.
The main threats facing plants in the modern world come from the ever-present habitat destruction and changing climate, but also from invasive species and disease. More than 5,000 species of plants have become invasive around the world, causing billions of dollars of damage, while diseases such as ash die back is driving a once common species to the edge. Hopefully, however, by having a definitive list of all known species, it gives scientists and conservationists a fighting chance to help them survive.
Image in text: Gilbertiodendron maximum is the largest and heaviest of all new species described from the West African rainforests of Gabon, and is already considered endangered. Johan van Valkenburg/Kew
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