Euphorbia tanaensis

Euphorbia tanaensis, commonly known as the Tana River euphorbia, is a critically endangered flowering plant within the family Euphorbiaceae. This species is endemic to a specific location along the Tana River in Kenya. Discovered initially as a group of nine specimens in 1988, a follow-up survey conducted in 2006 found only four remaining individuals, with no evidence of natural regeneration. The habitat of Euphorbia tanaensisis is under threat from ongoing deforestation.

Description
Euphorbia tanaensis is a medium-sized succulent, which can grow up to 30 m tall. It has a single trunk that may attain a diameter nearing 50 cm. The flowers are small and clustered into inflorescences known as cyathia.

Distribution and habitat
Euphorbia tanaensis is endemic to Witu, Kenya. Its estimated distribution range is confined to an area of approximately 4 km2, where it grows on the periphery of wet lowland forests, particularly those dominated by Terminalia zambesiaca. This specific ecological niche contributes to the plant's distinct characteristics and vulnerability.

Conservation
Euphorbia tanaensis is listed as Critically Endangered by the International Union for Conservation of Nature (IUCN). Within its endemic habitat, the population is estimated to comprise only four mature individuals. There are no records of this species in protected areas or ex situ conservation collections, and there has been no observed evidence of regeneration among the existing population.

Concerted efforts by community groups and forestry organisations have been made to restore the population. Notably, in 2018 several nursery-raised seedlings were planted in Witu and Kilifi’s Arabuko Sokoke forests.

As of August 2023, the Kenya Forestry Research Institute (Kefri) has engaged in captive cultivation of the plant in an effort to restore its population.

Threats
The primary threats to Euphorbia tanaensis are from human activities, particularly intensive logging within its habitat. Evidence of human disturbance, such as pole-cutting and the use of pit saws, have been observed close to its habitat. These disturbances are suspected to be a contributing factor in the species' decline.