Biodiversity loss has reached alarming levels, and disappearing with it are the secrets to finding treatments for pain, infections and a wide array of ailments such as cancer, they said, citing the findings of a coming book.

Achim Steiner, executive director of the United Nations Environment Programme (UNEP), said more than 16,000 known species are threatened with extinction, but the number could be more.

"We must do something about what is happening to biodiversity," he said at a news conference on the sidelines of the UN-backed Business for the Environment conference.

"Societies depend on nature for treating diseases. Health systems over human history have their foundation on animal and plant products that are used for treatment."

Technological revolution in the 19th and 20th centuries took the focus on finding cures away from nature as pharmaceutical companies relied on technical components to make medicines, he said.

These companies are increasingly turning back to nature as they run out of chemical combinations, he said.

But the world is "losing the intellectual patents of nature before we even have the chance to understand or unravel them," Steiner said.

"This is the tragedy of not understanding biodiversity," he said, adding it would be a "big fallacy" to think that biodiversity is not linked to the phenomenon of climate change.