Hundreds of medicinal plants are at risk of extinction, threatening the discovery of future cures for disease, according to experts.
Over 50% of prescription drugs are derived from chemicals first identified in plants.
But the Botanic Gardens Conservation International said many were at risk from over-collection and deforestation.
Researchers warned the cures for things such as cancer and HIV may become "extinct before they are ever found".
The group, which represents botanic gardens across 120 countries, surveyed over 600 of its members as well as leading university experts.
They identified 400 plants that were at risk of extinction.
These included yew trees, the bark of which forms the basis for one of the world's most widely used cancer drugs, paclitaxel.
Hoodia, which originally comes from Namibia and is attracting interest from drug firms looking into developing weight loss drugs, is on the verge of extinction, the report said.
And half of the world's species of magnolias are also under threat.
The plant contains the chemical honokiol, which has been used in traditional Chinese medicine to treat cancers and slow down the onset of heart disease.
The report also said autumn crocus, which is a natural treatment for gout and has been linked to helping fight leukaemia, is at risk of over-harvest as it is popular with the horticultural trade because of its stunning petals.
Many of the chemicals from the at-risk plants are now created in the lab.
But the report said as well as future breakthroughs being put at risk, the situation was likely to have a consequence in the developing world.
It said five billion people still rely on traditional plant-based medicine as their primary form of health care.
Report author Belinda Hawkins said:
"The loss of the world's medicinal plants may not always be at the forefront of the public consciousness.
"However, it is not an overstatement to say that if the precipitous decline of these species is not halted, it could destabilise the future of global healthcare."
And Richard Ley, of the Association of the British Pharmaceutical Industry, added: "Nature has provided us with many of our medicines.
"Scientists are always interested in what they can provide and so it is a worry that such plants may be at risk."