For more taxonomic information see Thulin (2020).

Boswellia samhaensis is a rare cliff-rooted frankincense tree, endemic to Samha, a small island in the Socotra Archipelago (Yemen). It is found exclusively on the top of a few small limestone boulders (together with Euphorbia arbuscula and Aloe spp.) at an altitude of 60–350 m asl. Recent surveys of current distribution, number of trees and assessment of threats were carried out in 2020–2023 by local Socotri and external specialists (Mendel University, La Sapienza, Ghent University; Franklinia-funded Boswellia project; Maděra et al. 2022, 2024) in the entire Socotra Archipelago, leading to an inventory of 244 trees of B. samhaensis which is found in only one single small location on Samha. We estimate the total global population of this species in the wild currently, at c. 250 trees. The extent of occurrence is 4 km² (0.06 km²) and the area of occupancy 4 km². The areas where this species is found, are inaccessible by goats, so overgrazing has pushed the local population of B. samhaensis nearly to extinction.

Because of its very limited distribution, this species is highly vulnerable to landslides, drought and other effects of climate change (these few trees are growing on one or two single boulders on a slope) and diseases, as well as to overgrazing by goats, which are common on Samha Island (young trees in browsing areas are absent). Illegal collection by succulent collectors also forms a severe threat, as this species has recently also appeared in international black markets for collectors.

Conservation efforts started in 2020 for B. samhaensis, resulting in increased awareness, local seed germination and establishing a nursery (on Samha Island) and are ongoing.

The species is listed as Critically Endangered due to its very small distribution area and low abundance of the trees in a single subpopulation and location, continuing decline is caused by threatened by climate change and overgrazing.

Boswellia samhaensis is restricted in its global distribution to Samha, a small island of the Socotra Archipelago (Yemen) where c. 250 trees survive in foothills on only four limestone boulders in the southwestern part of the island. The rare species has a restricted geographic range with an extent of occurrence of 0.06 km², and an area of occupancy of 4 km². Intensive surveys in the Socotra Archipelago (2020–2023; Maděra et al. 2024) indicate that this species is truly limited in its distribution to Samha Island.

Only one small population of Boswellia samhaensis is known from Samha Island within the Socotra Archipelago (Yemen), containing 244 inventoried individuals in 2020–2023 (total estimate 250 trees). All individuals are growing on top of four large isolated limestone boulders, which can be considered as a single location. One boulder hosts c. 172 trees, the others are less numerous. It is possible that there are some additional localities in Samha Island, however, the terrain is highly inaccessible; the indigenous people of the island were interviewed during recent surveys (2020–2023; Maděra et al. 2022, Maděra et al. 2024) and have no knowledge of more trees. The population trend is unknown, although there are some young trees in inaccessible areas, but the species is highly threatened by any local changes because of its very small distribution, and all trees in accessible areas are missing (eaten by goats).

Boswellia samhaensis is very rare species growing exclusively on top of large limestone boulders together with Euphorbia arbuscula and Aloe spp. at an altitude of 58–353 m in Samha Island (Socotra Archipelago). It is large shrub up to 2 m in height, mostly with tree-like shape with one stem and a small crown. This species has pinnate leaves (like B. bullata), and its flowers are red. In situ research on its biology has shown seed germination rates of 35% (Hamdiah et al. 2022), so there is an opportunity for local conservation and reforestation.

The endemic Boswellia species of the Socotra Archipelago undergo general challenges to the islands' terrestrial biodiversity as discussed in Van Damme and Banfield (2011), Attorre and Van Damme (2020) and Madĕra and Van Damme (2022). The challenges specifically to the endemic Boswellia in Socotra, including B. samhaensis, are reviewed in Maděra et al. (2024).

The specific threats to B. samhaensis have been assessed in detail in situ in 2020–2023 (Franklinia Project team; Madĕra et al. 2022, Madĕra et al. 2024). The species is sensitive to overgrazing and only occurs currently in one relict location, inaccessible to goat browsing. For the remaining (relict) population, no direct threats are noted, but there is a high potential for future impacts. This small remnant population is highly sensitive to landslides and other manifestations of global climate change (e.g., drought, heavy rains) which could wipe out the species in a single event. Illegal collection by succulent collectors should be monitored as well, as the species occurs in international markets recently.

There is no direct local use known for this species, which was only described in 2020 (Thulin 2020), therefore it is not listed in the ethnoflora of Miller and Morris (2004). It is a species without current value for local people due to its occurrence in inaccessible habitats. We foresee only a future conservation value for this species. Recently, this very rare species has also appeared in the international market through illegal export by succulent collectors in Socotra, posing as tourists. 

Specific conservation efforts for this threatened tree species (and other endemic Boswellia in the Socotra Archipelago) started in 2020, including the establishment of local nurseries, awareness, local seed germination and reforestation. One local nursery for B. samhaensis has been supported in Samha village (on Samha Island) in 2021, within the Boswellia project supported by the Franklinia Foundation (implemented by local teams in coordination with a consortium of Mendel, Sapienza and Ghent Universities and in cooperation with the local authority EPA).

The small population is highly sensitive to the manifestations of global climate change (cyclones, drought) and illegal collection by succulent traders. Local awareness, a species conservation action plan and replantation efforts of this species are important steps, complicated by the remoteness and high isolation of Samha Island. In addition, it is crucial that any illegal trading of this species by succulent collectors is stopped.