If you are in the Western world, you likely know the tale of the Three Wise Men who brought gifts for the baby Jesus. The value of gold is still obvious today, but while people have heard of myrrh and frankincense, most don't know what they were for, or why anyone would bring them all that distance to give to a newborn.

Frankincense and myrrh are fragrances that were quite valuable at the time and just as impractical for a baby as gold - but they are also still big business today, though not quite as valuable as gold. Just in Ethiopia, frankincense is a 4,000 ton per year industry. One Boswellia papyrifera tree from which the resin for frankincense is harvested will typically yield about 200g per year.

Ethiopia is the main exporting country and the resin is extracted much like maple syrup or anything else. The tree is tapped by wounding the bark and then they collect the resin released. Tapping is carried out at several spots along the stem, using a traditional type of tool that resembles a chisel, and the process is repeated in 8 tapping rounds during the dry season, which lasts about 8 months.

As more and more villagers become dependent on the industry, the high demand means that Boswellia trees are in danger of being over-exploited and populations are at risk of dying out. A new study by botanists could secure a more sustainable future for the trees, by revealing the anatomy of the resin secretory system.

Lead author Motuma Tolera explains, "In some areas, the high demand for frankincense is causing over-tapping, which is bad for a couple of reasons. Tapping the tree creates wounds in the stem that take resources to be healed, and more wounds create more opportunities for insects to attack the tree. It's not a surprise that some trees die. This is bad for the tree but also for the people living in those areas, since they depend on the resin production, both economically and culturally.

"One of the problems is the lack of knowledge of the type, architecture and distribution of resin producing, storing and transporting structures in the tree. Such knowledge is needed for improved tapping techniques in the future."

The findings have practical applications for the people of Ethiopia and other frankincense producers. Traditional tapping starts with a shallow wound, from which a relatively small amount of resin is released. The wound is then re-opened later with a cut that goes a bit deeper and more resin is collected – a process that is repeated over and over again. The amount of resin collected peaks after about 5 rounds of tapping, which the study suggests is the point at which the wound reaches the main region of resin canals. 

Motuma Tolera said, "What we found was a 3-D network of inter-connected canals in the inner bark. Most of these canals are within a very narrow region of the inner bark, in a zone that is less than 7 millimeters thick. These allow for the transport of resin around the tree. We also found a few canals connecting deep into the xylem, the heart of the tree.  

"Our results suggest that tapping can become more efficient. A cut that goes deeper, earlier in the tapping cycle, may drain the resin more effectively. Since the 3-D resin canal network may allow for long distance movement of resin when it is intact, this would be an option to reduce the number of cuts, and reduce the damage to the trees. New studies will be needed to show how such improvements may keep trees healthy but still productive for resin production. This opens new ways for a more sustainable frankincense production system.

"It's nice to discover something new, but here we also have the opportunity to give something back to the people who helped us with the study. I hope everyone in Lemlem Terara, but also elsewhere in Ethiopia, will benefit from what we have found in the future."

The team hope the results mean more Boswellia trees will live to see next Christmas.

Published in the Annals of Botany