The Three Kings carried it to Bethlehem, and its fragrance is synonymous with Christmas.

But frankincense, which can be  burned or infused into incense, oils and perfume, maybe doomed. Ecologists warn in a new study published in the British Journal of Applied Ecology that the population of trees in the Boswellia family that produce the fragrant resin is quickly diminishing.

According to the study,  if  the situation continues unchecked, frankincense production will drop by 50 percent  in 15 years, and the supply of Boswellia trees will plunge 90 percent  in the next 50 years.

Frans Bongers, a co-author of the study, says the findings send an "alarming message."

"The forests that remain are declining because the old individuals are dying continuously, and there [are] no new individuals coming into the system. That means that the forests are running out of trees,"  Bongers told the BBC.

"In places like Oman and Yemen, [trees are]  being cut down systematically. Now, in Ethiopia, [they're] being cut down as land is being turned over to agriculture," Bongers said.

Boswellia trees grow in the Horn of Africa and the Arabian Peninsula. The study looked at a dozen populations of Boswellia papyrifera trees in Ethiopia and found that despite the presence of young seedlings, none grew to become persistent saplings.

"Populations and frankincense production could only be sustained with intensive management leading to full sapling recruitment and a 50 to 75 percent  reduction in adult mortality," the study says.

In addition to  agriculture, the study also cites  fire, grazing and beetle attacks as threats to the Boswellia trees. And as the Boswellia tree goes, so goes  frankincense.