Serra Garuzo

A(i)Site contains one or more globally threatened species

Serra Garuzo qualifies as an IPA under criterion A(i), supporting two globally threatened species: Tannodia swynnertonii (VU) and Encephalartos manikensis (VU). There is a large and healthy population of the latter species for which Garuzo is the only site within Mozambique’s IPA network. The site also supports significant areas of Medium Altitude Moist Forest, a restricted and nationally threatened habitat, but is not considered to be among the best five sites nationally for that habitat and so Serra Garuzo does not qualify under criterion C(iii).

Serra Garuzo is a mountain ridge in Manica Province, to the east of Manica town and north of Bandula, straddling Manica and Vanduzi Districts. The ridge runs north-south for approximately 20 km, arising from a plain at ca. 700 m elevation and reaching a peak of just under 1,500 m. Numerous stream gullies run-off the ridge to the east and west. The IPA includes the whole length of the mountain ridge, up to 4 km wide and covering an area of approximately 50 km2. The site is not formally protected and the slopes on either side of the ridge are managed by different communities.

The Serra Garuzo IPA lies within the Chimanimani-Nyanga Highlands (Sub-) Centre of Plant Endemism (Darbyshire et al. 2019). Significant areas of medium altitude moist forest can be found at this site, though this habitat has become fragmented, particularly on the east side of the ridge. Medium altitude moist forest is a species-rich but restricted and threatened habitat in Mozambique. At Garuzo, the forest supports the threatened tree species Tannodia swynnertonii (VU) at one of only two known sites nationally, and the understorey herb Cyathula divulsa (VU) at its only known site in Mozambique. Species near-endemic to Mozambique, notably the forest tree Maranthes goetzeniana (NT; Timberlake et al. 2018) and the understorey shrub Pavetta comostyla var. inyangensis, also occur. The forest is not well-studied botanically and other interesting species are likely to occur here; one taxon of note is an undescribed species of Sansevieria (T. Rulkens, pers. comm. 2019). Garuzo is particularly noteworthy for supporting a healthy population of the threatened cycad Encephalartos manikensis (VU), which is found in open rocky sites and at forest margins. This cycad is known from only a few sites in Mozambique and Zimbabwe and is threatened by the illegal collection of wild plants for use in horticulture (Donaldson 2010). Other species of note in rocky areas and associated woodland at Garuzo are Aeschynomene sp. B of Flora Zambesiaca at its only known site (Verdcourt 2000), Huernia volkartii var. repens for which Garuzo is one of only four known sites globally, and the Chimanimani-Nyanga Highlands endemic Plectranthus chimanimanensis (LC).

The north-south montane ridge of Serra Garuzo is a part of the Frontier (Fronteira) Formation of the Precambrian Gairezi Group, comprising mica schists and quartzites; this formation has not been dated precisely (Instituto Nacional de Geológia 1987; Manhica 2012).
The medium altitude moist forest on the mountain slopes reaches a canopy height of 25 – 30 m, with large trees including Strombosia scheffleri, Myrianthus holstii, Vepris bachmannii and Zanthoxylum gilletii. The forest understorey includes both bare patches and areas of dense shrubs with Acanthaceae and Rubiaceae species often dominating. On the top of the ridge, montane grassland and rocky areas provide habitat for diverse herbs, shrubs, succulents and grasses; Loudetia simplex is locally dominant in the grassland whilst the more open slopes hold patches of the sedge Coleochloa setifera. Conspicuous succulents include Aloe cameronii and A. chabaudii. Patches of low miombo (Brachystegia) woodland are also found here and extend down the western slopes of the ridge. There is a greater extent of woody vegetation remaining on the western slopes than the eastern slopes, including both forest and woodland. Stream gullies in the mountain slopes provide further habitat diversity at this site, along gradients of slope and soil moisture.

The Serra Garuzo IPA is not currently protected or included within any conservation schemes. The following information on threats was gathered during fieldwork on the east side of the ridge in 2018 (Osborne & Matimele 2018). On the east side of the Garuzo ridge, much of the forest has been cleared for subsistence agriculture including cultivation of maize and yams (Colocasia esculenta). Remaining forest patches are healthy with only low levels of disturbance from selective timber cutting for local use. Some previously cultivated areas on the slopes have been recently abandoned following the prohibition of cultivation there by the government administrator (Chefe do Posto) in Vanduzi. Several dense patches of the invasive shrub Vernonanthura polyanthes were recorded on a rocky slope at ca. 1,350 m elevation. This shrub was originally introduced into Mozambique from South America as a nectar source for bees. It is a potential threat to the montane grassland and shrubland vegetation as it can form dense stands on disturbed and open ground.

Serra Garuzo has a high plant biodiversity value and provides an island of natural habitat for flora and fauna within the surrounding agricultural plain. The mountain ridge provides a watershed for the local area and the vegetation contributes to carbon sequestration and storage. The remaining forest has spiritual and cultural value for local communities and provides timber for local use. In addition, the site supports populations of at least two socio-economically important plants, Encephalartos manikensis, a cycad valued in the horticultural trade, and Coffea mufindiensis subsp. australis, a wild relative of coffee.

Jo Osborne, Royal Botanic Gardens, Kew

Iain Darbyshire, Royal Botanic Gardens, Kew