Palo santo: the importance of botanical names

I recently received an email that brought to my attention a common misperception that is deserving of attention. The email stated:

I am writing you as someone who enjoys and is interested in palo santo, specifically bursera graveolens. After reading that it was endangered in articles like yours, I stopped using it completely – actively campaigning against its use whenever I could.

However, after further research, I am starting to think there is some confusion. There are two species of palo santo, bursera graveolens and bulnesia sarmientoi. The links I provided are to the IUCN reports for each species. If you visit them, you can see that bursera graveolens is not actively considered an endangered species.

You are wrong – palo santo is endangered – but not all species of it. I believe that you are incorrect in listing bursera graveolens as endangered in your article. This confusion seems to be widespread.”

Firstly, it is critical to understand the importance of botanical names, a.k.a. scientific Latin names. Botanical names are universally recognized and help to reference plants in a number of fields. A botanical name such as Bursera graveolensbegins with the genus name (Bursera) followed by the species name (graveolens).

Botanical names are not functional in the same way as common names in that common names are not recognized universally and scientifically, and different species may be known by the same common name. For example, the common name ‘palo santo’ is used by locals in different geographic regions to describe two very different species Bursera graveolens and Bulnesia sarmientoi. Unlike a botanical name, common names have no bearing on the scientific differentiation of species.

Species differentiation takes many forms including they 1) fall under the same genus, or 2) belong to different genera. Take the genus Bursera for example – one species of Burserais graveolens (Bursera graveolens) and another is morelensis (Bursera morelensis)An example of two distinct species which belong to different genera is again Bursera graveolens (Figure 1) and Bulnesia sarmientoi (Figure 2).

Figure 1. Bursera graveolens commonly known as palo santo and holy wood. Photo credit: Maša Sinreih in Valentina Vivod – Own work
Figure 2. Bulnesia sarmientoi commonly referred to as palo santo, holy wood, and guaiacwood.

What confuses many people about these two distinct species is that they are both referred to ‘commonly’ as palo santo or holy wood. And just to add to the confusion, or rather to further clarify, Bulnesia sarmientoi is also referred to commonly as guaiacwood. So, although these two species share some common names they are vastly different. For example, Bursera graveolens essential oil consists primarily of limonene, menthofuran, and a-terpineol; whereas Bulnesia sarmientoi essential oil consists primarily of bulnesol, guaiol, and 10-epiy-eudesmol (see Tisserand and Young, 2014).

Common names lead to the kind of misunderstanding that can adversely impact how we support and perceive the conservation status of these species; therefore, always work from the standpoint of the botanical name. 

Bulnesia sarmientoi is classified as endangered by the IUCN and is trade-protected by CITES. Bursera graveolens is not endangered, it is possibly in more peril having received the status as critically endangered in Peru per the 2005 Global Forest Resource Assessment (GFRA) which follows guidelines set out by the IUCN. Although this status may have changed since 2005, unless there is absolute evidence stating otherwise, we advise working with the species as reflected by the most recent assessment. 

Also bear in mind that threatened plants are native and/or cultivated in more than one country. Although Bursera graveolens is native to Peru, it also is found in Ecuador where population numbers of Bursera graveolens are seemingly quite stable. Regardless of location, it is highly advisable that when sourcing essential oil extracted from Bursera graveolens or Bulnesia sarmientoi that the growers/harvesters/processors  can demonstrate sustainable management through certification, particularly when sourcing material or oils from those countries where there is less stable infrastructure in place to protect the plant as evidenced by assessments done not just through the IUCN (global or regional), but also noted in a GFRA. Other organizations we use to identify threatened species include WWF, the US Fish and Wildlife, and NatureServe.

It is also important to always have a good understanding of what part(s) of the trees are being used to extract essential oil or plant material for burning. Sustainable harvesting of trees includes extraction of the felled wood and/or branches, and there is evidence that the trees are being replanted. 

And finally, we have never advised people to stop using essential oils from these species; however, we encourage you to only do so if sustainable, ethical, and legal sources have been verified. Sources like these not only help to protect threatened and near-threatened plants, but they also help to enrich communities, many of which represent Indigenous people who equally rely on these plants for their use in traditional medicine. 

Warmly,

Dr. Kelly

Reference

Tisserand and Young 2014. Essential Oil Safety: A Guide for Healthcare Professionals. 2nd Edition. Elsevier.