Plants are as threatened as mammals, with one in five of the world’s plant species threatened with extinction. It is for the first time that the true extent of the threat to the world’s estimated 380,000 plant species has been quantified.
The shocking numbers come from the Sampled Red List Index assessments carried out by Royal Botanic Gardens Kew, the Natural History Museum and the International Union for Conservation of Nature (IUCN) Specialist Groups. The findings have been released ahead of the United Nations Biodiversity Summit to be held at Nagoya, Japan in mid-October. This year is being observed as the United Nations' International Year of Biodiversity.
The scale of the task facing botanists is humongous. About one third of the species (33 percent) in this representative sample were insufficiently known to even assess. Many plants are so poorly known that scientists still do not t know if they are endangered or not.
Of the almost 4,000 species that were carefully assessed, over one fifth (22 percent) were classed as Threatened. Among plants, gymnosperms (the plant group including conifers and cycads) were found to be the most endangered group. Most threatened plant species have been found in the tropics.
The most threatened habitat is the tropical rain forest. The current rate of loss of tropical forest accounts for 20 percent of global carbon emissions, the study has found. Moreover, the most threatening process was seen to be man-induced habitat loss, mostly the conversion of natural habitats for agriculture or livestock use.
Kew’s Director, Professor Stephen Hopper, summed up the scenario in a statement, “This study confirms what we already suspected, that plants are under threat and the main cause is human-induced habitat loss. For the first time we have a clear global picture of extinction risk to the world’s known plants. This report shows the most urgent threats and the most threatened regions. In order to answer crucial questions like how fast are we losing species and why, and what we can do about it, we need to establish a baseline so that we have something against which to measure change.”
The Sampled Red List Index for Plants has been developed as a new tool to monitor the world's plant life. The project will involve reassessments at regular intervals which will chart the changing fortunes of the world’s plants; much like a stock exchange index shows the ups and downs in the value of shares.
The task of assessing the threat to the world’s plants is itself is a challenge. The number of plant species is estimated at around 380,000 species, which is much larger than the numbers of birds (9,998 species), mammals (4,000 species) or amphibians (6,433 species). A sampled approach, therefore, was needed.
At the onset, 7,000 plant species were drawn from the five major groups of plants. Both common and rare species were assessed in order to give an accurate picture of how plants are faring around the world. Next, 1,500 species were selected at random and each assessed against the IUCN Red List Index categories and criteria.
