Distribution

Endemic to East Africa where it occurs in Tanzania and Kenya (Kyulu Hills, Taita Taveta District).

Habitat and Ecology

It occurs in montane evergreen rainforest and dry evergreen forest, mixed with co-dominant angiosperms. Elevation ranges from ca. 1500m to ca. 3000m. above sea-level. Trees are often solitary but not emergent, only reaching into the general canopy of the forest. In rainforests it often occurs with Podocarpus milanjianus; the co-dominant angiosperm tree in this wetter forest type is often Ocotea usambarensis, but many other species may occur with it. In dryer evergreen forest Olea and Ficus are common associates and it also occurs with Calodendrum capense, Syzygium cordatum and Bridelia micrantha. These drier forests are often degraded or converted to coarse grassland in which A. usambarensis can survive as isolated trees, at least for a time.

Conservation Status

Global status

Endangered A2cd+4acd; B2ab(ii,iii,iv,v)

Global rationale

Whereas the past and future population size reductions here given are suspected on the basis of localized observation and general reporting about (illegal) logging and deforestation, and therefore remain rough estimates, there is no doubt that this situation is continuing despite the establishment of many forest reserves. Deforestation outside these reserves has reached high proportions as seen from Google Earth satellite images, so the Area of Occupancy (AOO) calculated on known localities from herbarium collections past and present (some may no longer represent actual living trees) is here based on a grid of 5km (probably somewhat generous with 41 collections from 20 localities) and thus falls below the threshold for Endangered under criterion B (< 500km²). A past reduction of more than 50% is estimated to have occurred since 1950: given current rates of deforestation and ongoing illegal logging, an overall decline of between 50 and 80% is projected to have occurred by 2030. This is within the three generation period required under the IUCN guidelines and therefore leads to an assessment of Endangered under the criteria for A2 and A4.

Global threats

This species is under severe threat from illegal logging in the Chome Forest Reserve in Tanzania (evidence from aerial photography); the same type of saw pit exploitation is known from other locations. General deforestation and fires are also reducing the rainforest, which is usually limited in extent even naturally. This species is the most valuable and specifically targeted tree for (illegal) logging in this type of forest. As a result of these threats the global population is highly fragmented.

Conservation Actions

This species is present in the following forest reserves in Tanzania: Chome, Hanang, Mafwomero, Mkusu, Nou, Shagayu and Wotta. Several of these have been included in the nomination of the Eastern Arc Mountains for World Heritage status and some of them are also due to be upgraded to Nature Reserves. Illegal logging is ongoing.