Every fifth plant species is threatened with extinction, which means the world's plants are as much at risk of dying out as mammals, according to a study conducted by the Royal Botanic Gardens, Kew, together with London's Natural History Museum and the International Union for the Conservation of Nature (IUCN).

The researchers created a portrait of the status of life on earth and how life is changing by measuring the extinction risk and biodiversity.

Called a "barometer of life," the Sampled Red List Index for Plants will serve as a baseline for the state of the world's estimated 380,000 plant species.

The study, which showed that tropical rain forests represent the most threatened habitat, was published as governments are to meet in Nagoya, Japan, in mid-October to set new targets at the United Nations Biodiversity Summit.

Risk assessment big challenge

Assessing the threat to the world's plants is a bigger challenge than that of rating threats to birds, mammals, or amphibians because there are significantly more plant species than there are birds (10,027 species), mammals (5,490 species) or amphibians (6,285 species).

In order to assess the extinction risk, the researchers took a representative sample of the world's plants in which 1,500 species were randomly selected from each of the five major groups of land plants.

Insufficient knowledge about a third of the species in the sample left researchers unable to assess whether the plants were endangered.

While evolution and natural attrition account for some plant loss, 81 percent of the threats are manmade, including the transformation of natural habitat to agriculture, development and logging, according to Justin Moat, a researcher at the Royal Botanic Gardens Kew.

"Plants are fundamental to life on earth, they are the base of the food chain, we depend on them for food, shelter, clean water, regulating the climate and lots more," he said, adding that a plant's extinction could have unexpected consequences.

"Think about removing or tinkering with the wrong nut in a car, it will soon end up ruined," he said.

Foundation of biodiversity

The Red List Index represents a crucial tool to monitor change in plant species, according to Royal Botanic Gardens, Kew's Director Stephen Hopper.

"Plants are the foundation of biodiversity," he said. "Their significance in uncertain climatic, economic and political times has been overlooked for far too long. In a time of increasing loss of biodiversity it is entirely appropriate to scale up our efforts."

This accelerated loss of plant species means a direct threat to mankind, UK's Environment Secretary Caroline Spelman warned.

"Plant life is vital to our very existence, providing us with food, water, medicines, and the ability to mitigate and adapt to climate change," she said.

Author: Nina Haase (sms)

Editor: Nathan Witkop