Production of frankincense could be cut by half in the next 15 years due to steep declines in the number of the trees that make the resin, researchers have warned.
Frankincense, used in incense and perfume and one of the gifts brought by the three kings in the Christmas story, is produced by tapping Boswellia trees for their resin.
But numbers of the trees, which grow in the Horn of Africa and the Arabian peninsula, are declining so steeply that they could be down 90% in the next 50 years if action is not taken to preserve the species, researchers predicted.
A study published in the British Ecological Society's Journal of Applied Ecology of 12 populations of Boswellia trees in Ethiopia suggests that the species is being hit by fire, grazing and insect attack.
Adult trees are dying at the rate of 6% to 7% a year, the two-year study of more than 6,000 Boswellia trees and seedlings by Dutch and Ethiopian ecologists found.
The adult plants are thought to be dying as a result of beetle attacks and fire. High incidence of fire could make the trees more susceptible to the beetles. And seedlings were failing to grow into saplings because increases in cattle herds in the area led to more burning, to encourage new plant growth for fodder and grazing, the researchers said.
There was no difference between populations of trees which were tapped for frankincense and those which were not - indicating the problems faced by the trees were not the result of harvesting the resin.
But study of a remote population of Boswellia, which was not subject to burning or grazing, showed it had lower rates of mortality, fewer signs of beetle attack and no detectable signs of fire.
Dr Frans Bongers, of Wageningen University in the Netherlands, said: "Current management of Boswellia populations is clearly unsustainable. Our models show that within 50 years populations of Boswellia will be decimated, and the declining populations mean frankincense production is doomed."
The researchers said efforts were needed to stop fires to prevent high death rates among adult trees, although controlling the beetles was harder. Long-term management was also required, with areas protected from ground fires and grazing for long enough to allow saplings to establish themselves.