Conservation news

How many plant species are there in the world? Scientists now have an answer

  • There are about 391,000 species of vascular plants currently known to science, of which about 369,000 species (or 94 percent) are flowering plants, according to a report by the Royal Botanic Gardens, Kew, in the United Kingdom.
  • About 2,000 new plant species are discovered or described every year, many of which are already on the verge of extinction.
  • Based on the best available estimate, scientists say that 21 percent of all plant species – or one in every five plant species – is likely threatened with extinction.

For the first time ever, scientists have assessed the state of all vascular plants in the world — all plants (except algae, mosses, liverworts and hornworts) that have specialized tissues to transport food and water.

According to the report titled “State of the World’s Plants”, released by researchers at the Royal Botanic Gardens, Kew, in the United Kingdom, there are about 391,000 species of vascular plants currently known to science. Of these, about 369,000 species (or 94 percent) are flowering plants.

The report provides — for the first time — baseline information on all vascular plants, including new plant discoveries and threats.

“We already have a ‘State of the World’s …birds, sea-turtles, forests, cities, mothers, fathers, children even antibiotics’ but not plants,” Kathy Willis, Director of Science at the Royal Botanic Gardens, Kew, said in a statement. “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.”

Springville clarkia, endemic to California, is a rare species of flowering plant in the evening primrose family. Photo by US Forest Service, Public Domain.

By scanning through several plant databases, including the the Plant List, the International Plant Names Index and the World Checklist of Selected Plant Families, the team found that 391,000 vascular plants are currently known to science. Moreover, about 2,000 new plant species are discovered or described every year. Many of these newly described are already on the verge of extinction.

In 2015, for example, scientists described Gilbertiodendron maximum, a critically endangered giant, heavy tree weighing about 105 metric tons, that is found in the Cameroon-Congolian African rainforest. Researchers also described Oberholzeria etendekaensis, a succulent shrublet, which is not only a new species but a whole new genus. It is also a rare species, known only from a single locality with 30 individuals in Namibia.

According to the report, Australia, Brazil and China are the top three sources for many of the new species discovered every year. In fact, the report notes that Brazil is home to more seed plants than any other country in the world, and the knowledge of its flora is growing at a “record-breaking” pace.

We share space with nearly 400,000 plant species. But so far, only about 31,000 of these species have at least one documented use. These include uses for food, medicine, recreation, genes, poisons, animal feed, and building material.

Top documented uses of plant species. Graphic: Mongabay; Source: Royal Botanic Gardens Kew: State of the World’s Plants.

The future looks bleak for many species, the report warns. Based on the best available estimate, scientists say that 21 percent of all plant species — or one in every five plant species — is likely threatened with extinction. The biggest threats are large-scale destruction of habitat for agriculture, such as for oil palm plantations, logging, livestock farming as well as residential and commercial. Mangroves and tropical coniferous forests have been most affected by the rampant land cover change, researchers found.

Climate change, too, is a threat, but a small one currently. However, it is likely to grow into a bigger threat in the coming years, researchers say.

“I suspect we won’t actually see the full impact until 30 years down the line as it takes so long for plants, especially trees, to produce their offspring,” Willis told the Guardian.

Some areas in the world still have a large diversity of plants, including several unique species. But only a few of them are actually legally protected, the report notes. Overall, researchers identified 1,771 important plant areas in the world that need urgent conservation action.

The results are sobering. But there are still plenty of information gaps that need to be filled, scientists say.

“To have effect, the findings must serve to galvanise the international scientific, conservation, business and governmental communities to work together to fill the knowledge gaps we’ve highlighted and expand international collaboration, partnerships and frameworks for plant conservation and use,” Willis said.

Baobab tree in Ankarana Madagascar. Photo by Rhett Butler.