The new report, to be published later this year, suggests that two-thirds of the 50,000 medicinal plants in use are still harvested from the wild, and between 4000 and 10,000 of them may now be endangered.
The findings, revealed by the New Scientist this week, lay the blame at the feet of the herbal industry, which has not ensured sustainability of its supplies.
The market for herbal remedies in North America and Europe has been expanding by about 10 per cent a year for the last decade and the world market is now thought to be worth at least £11 billion (€15.8bn), according to the study by Alan Hamilton, a plant specialist from the global environment network WWF, due to be published in Biodiversity and Conservation. In some countries, up to 80 per cent of the population relies on this form of treatment.
But Hamilton claims that many of the plants are harvested by poor communities in India and China whose livelihoods will suffer if the plants die out. The scientist has also helped compile a report, Herbal Harvests with a Future, to be released next week by the conservation group Plantlife International.
"With demand and commercialisation growing fast, the future of the wild plants which have helped most of humanity for centuries is now more uncertain than it has ever been," Martin Harper from the UK-based organisation told the New Scientist.
The group highlighted a number of species under threat, including tetu lakha (Nothatodytes foetida), a small tree found in rainforests in south India and Sri Lanka and used for anti-cancer drugs in Europe, and a saw-wort known as costus or kusta (Saussurea lappa) from India whose root is used for chronic skin disorders.
Plantlife accuses the herbal medicine industry of failing to ensure the sustainability of its supplies. It claims to have found that 11 of 16 herbal companies in the UK, harvest all the plants they sell from the wild, and the remaining five grow only a small proportion. UK consumers spend more than any other Europeans on herbal supplements each year, around £126 million a year according to a recent Mintel report.
The New Scientist article also cites an international expert on medicinal plants, Gerard Bodeker from Green College, Oxford, who believes the assessments of the crisis by Hamilton and Plantlife are conservative. Most of the processes involved in supplying the growing market for herbal remedies are "the result of unsustainable and often destructive practices driven by poverty", he tells the magazine.
The Plantlife report urges the industry to invest in cultivation and also proposes the introduction of a kite mark to identify products that have been sustainably harvested.
"I think this is a great idea. Not all herbal manufacturers are stripping the land of its resources and this would allow consumers to identify the products derived from sustainable practices," Sato Liu, executive director of the Natural Medicines Society (NMS), a charity supporting users of herbal medicine, told NutraIngredients.com.
"I think there is a need for awareness of this issue to be increased," she added.
A number of organisations including NMS and the WWF established the Herbal Sustainability Forum in 2001, which could put pressure on suppliers thought to be in the process of endangering a certain species.