Socotra Island, known as the Galápagos of the Indian Ocean, hosts an unusual diversity of plants found nowhere else on Earth. Nine of these endemic plant species, belonging to the genus Boswellia, are now closer to extinction, according to the IUCN, the global wildlife conservation authority.
Boswellia is an “iconic genus,” Frans Bongers, a professor of tropical forest ecology at Wageningen University & Research in the Netherlands, told Mongabay by email. The shrub-like trees, found in parts of Africa, southern Arabia and the Indian subcontinent, produce an aromatic resin called frankincense that’s been used worldwide for centuries in incense, perfumes and traditional medicine.
Of the 24 known Boswellia species, 11 are only found on Socotra Island, off the coast of Yemen.
The IUCN’s latest assessment reveals that five of the island’s Boswellia species — Boswellia ameero, B. elongata, B. bullata, B. dioscoridis and B. popoviana — have moved from vulnerable to endangered on the IUCN Red List since the last assessment in 2004. One species, B. nana, has plunged even further, from vulnerable to critically endangered.
Three species — B. samhaensis, B. hesperia and B. scopulorum — were scientifically described only after the 2004 assessment. Their first IUCN Red List assessment now categorizes them as critically endangered. All three species have both small populations and limited distribution, said Petr Maděra, a professor of forest botany at Mendel University in the Czech Republic. Maděra is an assessor for the IUCN Red List status of Boswellia trees and coordinates the Socotra endangered project, supported by the Franklinia Foundation and Mendel University.
Socotra’s Boswellia trees are currently not the main source of commercially traded frankincense, although the island was historically part of the incense trade, researchers say.
Today, there are two major drivers behind the trees’ decline, Maděra said. Overgrazing by livestock like goats affects saplings and smaller plants, limiting natural regeneration; while extreme weather events like cyclones linked to global climate change destroy mature trees. For instance, cyclones Chapala and Megh that struck Socotra in 2015 destroyed an estimated 308 B. elongata trees, while 230 more died in the next two years.
Bongers said habitat fragmentation due to agriculture and infrastructure development are also reducing the suitable sites where the plants can grow.
Newer threats have also emerged. For instance, B. nana, which only grows on steep limestone cliffs in the northeastern part of Socotra Island, has recently started “being illegally exported and sold in international markets by succulent collectors,” the species’ IUCN page notes.
Bongers said measures like reducing grazing by goats, better management of stormwater, and planting and protecting the trees in the right areas could all help halt the decline of Boswellia trees. It’s also important for the local population to see the advantage of having these species, he added, especially where the trees have a local cultural value or attract tourists.
Banner image of a Boswellia tree on Socotra Island by Alexandre Baron via Flickr (CC BY-NC-SA 2.0).
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