Knowledge of medicinal plants is at risk of disappearing as human languages become extinct, a new study has warned. Indigenous languages contain vast amounts of knowledge about ecosystem services provided by the natural world around them. However, more than 30% of the 7,400 languages on the planet are expected to disappear by the end of the century, according to the UN. The impact of language extinction on loss of ecological knowledge is often overlooked, said the study’s lead researcher, Dr Rodrigo Cámara-Leret, a biologist from the University of Zurich. “Much of the focus looks at biodiversity extinction, but there is a whole other picture out there which is the loss of cultural diversity,” he said. His team looked at 12,000 medicinal plant services associated with 230 indigenous languages in three regions with high levels of linguistic and biological diversity – North America, north-west Amazonia and New Guinea. They found that 73% of medicinal knowledge in North America was only found in one language; 91% in north-west Amazonia; and 84% in New Guinea. If the languages became extinct, the medicinal expertise associated with them probably would too. Researchers expect their findings from these regions to be similar in other parts of the world. “The loss of language will have more critical repercussion to the extinction of traditional knowledge about medicinal plants than the loss of the plants themselves,” said Cámara-Leret. The areas with languages most at risk were in north-west Amazonia, where 100% of this unique knowledge was supported by threatened languages, and in North America, where the figure was 86%. In New Guinea 31% of languages were at risk. The anticipated loss of linguistic diversity would “substantially compromise humanity’s capacity for medicinal discovery”, according to the paper, published in PNAS. Such knowledge includes using the latex of plants to treat fungal infections, using bark to treat digestive problems, fruits for respiratory ailments, as well as natural stimulants and hallucinogens. “The list goes on and on, it’s quite impressive,” said Cámara-Leret. “Even the best plant taxonomists out there are amazed by the breadth of knowledge of indigenous cultures, not only about plants but also animals and their inter-relations.” It is impossible to know what has already been lost. More than 1,900 of the languages spoken now have fewer than 10,000 speakers and the UN has declared 2022-32 to be the International Decade of Indigenous Languages in recognition of this issue. Jordi Bascompte, an ecologist from Zurich University and second author of the paper, said European medicinal knowledge may represent the “tip of the iceberg”. Although a lot of drugs are based on synthetic compounds, there may be many more chemical components provided by plants that could unlock the potential for new treatments. “Any insight, regardless of where it comes from, may end up being useful,” he said. The paper did not examine to what degree medicinal services are considered effective in the western sense, although researchers say that in many instances plants had proved effective. Much of the world’s linguistic diversity is being safeguarded by indigenous people whose culture and livelihoods are under threat as barriers between groups are broken down. Unlike societies where information has been transcribed in books and computers, most indigenous languages transmit knowledge orally. Governmental programmes to stimulate the transmission of languages, bilingual schooling and interest in cultural heritage would help communities retain linguistic diversity, said Cámara-Leret. But the medicinal aspect was just one of many reasons to promote the conservation and diversity of languages in the world, he added. Dr Jonathan Loh, an anthropologist and conservationist from the University of Kent, who was not involved in the research, said he was surprised by the degree of linguistic uniqueness in medicinal plant knowledge. He has previously spoken about the parallels between linguistic and biological diversity, commenting that these had evolved in remarkably similar ways, and both faced an extinction crisis. He said it was important, however, not to focus on utilitarian arguments for the conservation of languages, cultural diversity and biodiversity. “There may be valuable knowledge of medicines unknown to western science contained within these languages, and doubtless that is true to some extent, but it is not the most important reason for conserving them,” he said. “Every indigenous language and culture is a unique evolutionary lineage that once lost is lost forever.”