Mount Yao

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

Mount Yao qualifies as an IPA under sub-criterion A(i), hosting the only known population of the Vulnerable species Moraea niassensis. The vast majority of the botanical diversity of this site has not yet been documented and it is highly likely that further investigation will reveal more plant species of conservation interest.

Mount Yao (or Jao) IPA is located in Mavago District of Niassa Province. Located ca. 180 km east of Lake Malawi, this inselberg falls within Niassa Special Reserve and peaks at 1,313 m. The area has not been extensively studied; however, available evidence indicates it is botanically interesting as the high altitudes provide a cooler and wetter climate compared to the wooded plains that dominate the surrounding area. The mountain is largely dominated by dense miombo woodlands, with forest and swamp habitat associated with river gullies (Congdon & Bayliss 2013).
The site has been delineated to surround the main montane habitats, covering an area of 183 km2. The south-east and eastern boundaries run parallel with the Mataca-Mecula Road, with the south-eastern portion of this IPA falling 2 km from the boundary between Niassa Reserve and the Buffer Zone. The town of Mataca lies 20 km to the south-west while Maswise village is just 9 km south of the IPA boundary. The IPA itself is not populated by people and is largely undisturbed. Alongside the high-quality habitats, there are known to be a number of Mozambican endemic species from various taxa occurring on this mountain, some known from this site alone. Thus far, only a limited number of botanical collections have been made from this site, but it is likely to harbour more plant species of conservation importance than are currently known.

Mount Yao is primarily of botanical importance due to the presence of Moraea niassensis, a Vulnerable species known only from this IPA. This species was collected in 2012 from mid-altitude, dense woodland. There was only one population observed and this was estimated to be below the IUCN Red List D1 threshold of 1,000 individuals (Goldblatt et al. 2014), although the true value is likely smaller. Searches for this species were undertaken in similar habitat on the nearest inselberg, Serra Mecula located around 130 km east of this IPA, but to no avail, suggesting this species is endemic to Mount Yao (Goldblatt et al. 2014).
There has only been a handful of botanical collections made at this site, and so it is highly likely more taxa of conservation interest will be recorded from this site with greater collecting effort. Alongside Moraea niassensis there are a small number of faunal taxa endemic to this inselberg or found both here and on Serra Mecula. The relative isolation of the mid-altitude habitats on this inselberg may have allowed for the evolution of endemics in several different taxa. There is, therefore, a strong case for a comprehensive inventory of the plant taxa of this IPA.
Although the habitats of this IPA are high-quality and warrant further investigation, they cannot currently be assessed as threatened or restricted. There appears to be no montane forest on this inselberg, while the other habitats, riverine forest and varying densities of miombo, are widespread, despite the unique species associated with this habitat on Mount Yao.

Mount Yao is a largely wooded IPA, ranging from lowland miombo to dense montane miombo on the slopes, with some areas of gallery forest around rivers on the mountain (Spottiswoode et al. 2016). The inselberg is a granite intrusion of 1,313 m near the border of the Marrupa and Unango geological complexes, both of which are primarily dominated by orthogneisses (Boyd et al. 2010). Temperatures for Mavago district range from 15 – 22°C in June and July to 21 – 29°C in October and November, while average annual rainfall is 1,887 mm, with most of this precipitation falling between December and March (World Weather Online 2021). The upper slopes and summit of the mountain also receive moisture through mists, as is evident by the high number of Usnea epiphytic lichens.
Despite its interesting botany and pristine habitats, few botanical collections have been made on Mount Yao. One zoological visit was made in 2012 (Congdon & Bayliss 2013), focussing primarily on butterfly taxa, during which the few botanical specimens from this site were collected.
The plain surrounding Mount Yao is categorised by Lötter et al. (2021) as moist miombo, typical of this part of northern Mozambique, although Congdon & Bayliss (2013) describe this vegetation as more like coastal woodland. There is no species inventory for this area, but the plains and lower slopes are dominated by Brachystegia, most likely B. boehmii (C. Congdon, pers. comm. 2021).
The montane habitats were documented by Congdon & Bayliss (2013) and the description below is based upon this account and personal communications with C. Congdon (2021).
The slopes of the inselberg are steep around the base with a rocky substrate. Soils here are poor, likely due to natural erosion (C. Congdon, pers. comm. 2021). Uapaca kirkiana and U. sansibarica dominates miombo here, with a more open canopy, patches of suffritcose Cryptosepalum (likely C. maraviense) and a short, grassy understorey. Herbaceous understorey species have not yet been documented; however, grass species such as Hyparrhenia filipendula, Themeda triandra, Panicum and Urochloa spp. are known from montane miombo in this part of Mozambique (Lötter et al. 2021). At altitudes of around 1,000 m, this woodland also hosts the only known population of Moraea niassensis (VU).
Gallery forests, featuring species such as Parinari excelsa, Bersama abyssinica and Anthocleista grandiflora, occur near rivers and in gullies. The understory includes shrubs such as Drypetes gerrardii while herbs such as Justicia striolata and Afromomum sp. occur beneath. A red flowered legume, that appeared similar to a Desmodium, was found to dominate the forest floor within these areas. Collection of this legume is recommended in order to identify the species. Due to their strong association with rivers and streams, the boundaries of these riverine forests are well defined with Albizia, probably A. adianthifolia, occurring in the ecotone between forest and woodland.
The gallery forests are likely underlain by deep, nutrient-rich, moist soils, as have been reported from similar forests on Serra Mecula (Timberlake et al. 2004), with swamp forest occurring in areas of poor drainage. The species composition of these swamps has not yet been recorded, however, one patch was noted to have open pools of water, with little understory growth, and tree species with aerial and buttress roots. It is possible that Uapaca lissopyrena, a swamp tree with stilt roots, occurs in these areas as this species was recorded from swamps on the nearest inselberg, Serra Mecula (Timberlake et al. 2004).
Around the summit, vegetation cover is open, with a rocky substrate, and may be categorised as cloud or elfin woodland. The area receives moisture through frequent mists and, as such, Usnea lichens, known from several moist montane habitats in Mozambique, are common epiphytes in the area. These epiphytes were observed on large, old Brachystegia spiciformis trees. The presence of these old trees may suggest that the vegetation in this area has remained undisturbed for some time. The woodland also features species such as Parinari curatellifolia, Uapaca kirkiana, U. sansibarica alongside Bridelia, Pericopsis (likely P. angolensis), Monotes and Vitex species. The understory features shrubs such as Maesa lanceolata, Annona senegalensis and Dombeya (possibly D. burgessiae) with tussocky grasses in crevices in the rock. Hemi-parasitic Agelanthus sp. (on Pericopsis) and Viscum shirense (on Bridelia) were observed in this woodland, as were a number of epiphytic orchids. At higher altitudes the woodland thins, the shrub Protea angolensis becomes more prevalent, and in rockier areas closer to the peak, Protea welwitschii and Combretum species were observed.

Mount Yao IPA falls within Niassa Special Reserve, with the south-western portion, around 100 km2 in area, falling inside the reserve buffer zone where a number of small villages are located. In addition, this IPA falls within in the wider Niassa Special Reserve Key Biodiversity Area.
This site and surrounding areas have been categorised as receiving “limited conservation efforts” by the Wildlife Conservation Agency (Luwire Wildlife Conservancy 2019). However, the habitats throughout this IPA are largely pristine and have seen little disturbance - an abandoned Portuguese helicopter base is the only major sign of previous human activity on the inselberg itself (Congdon & Bayliss 2013). This area of Mozambique was largely depopulated due to conflict relating to the independence struggle and later the Mozambican Civil War (C. Congdon, pers. comm. 2021), so the anthropogenic threats in this area are generally quite low, particularly in comparison to other parts of Mozambique.
While anthropogenic disturbance within the IPA is currently minimal, the nearby town of Mataca, and associated agriculture, has continued to expand over recent decades, as has Msawise village, on the eastern side, to a lesser degree (Google Inc. 2020; World Resources Institute 2021). It is thought that, with continued population expansion in the area, anthropogenic disturbance may increase within the IPA, including cutting of woodland for fuel, clearance of land for agriculture and increased fire frequency (Datizua 2020).
The soils in the reserve are known to be generally of poor fertility and rainfall is low (Timberlake et al. 2004). Abandonment of exhausted agricultural land may, therefore, become an issue as it could result in further agricultural expansion, possibly onto the hills in the south of the IPA or on the mountain itself. Soils on the lower slopes of Mount Yao are thin and rocky (C. Congdon, pers. comm. 2021), and are unlikely to be highly productive, however there may be greater or more consistent moisture availability on the mountain, due to frequent mists, which may encourage small scale cultivation of these areas.
Although there was no evidence of fire within the forests at the time of the 2012 visit (Congdon & Bayliss 2013), fire has been reported elsewhere in the reserve as a method for clearing land for machambas and for subduing bees to allow for honey collection (Timberlake et al. 2004; T. Alves, pers. comm. 2021), and so there may be an additional threat of unintentional burning of huge swathes of land. It is particularly important that, if land is opened up for tourism, the practice of burning vegetation to create and maintain walking trails and vehicle access, as has previously been reported on and around Serra Mecula, is not also employed within this IPA.
Niassa Reserve does not currently receive much tourism, with only 183 visitors in 2013. The reserve, therefore, has limited income for funding conservation projects or supporting alternative livelihoods for local people. As well as providing income, tourism could incentivise the protection of wilderness areas such as Mount Yao which contribute to the visitor experience. More recently, there has been government-backed promotion of Niassa, including specific mention of Mount Yao, as a tourist destination (ANAC 2018), which may lead to greater interest or investment into the site.
As well as hosting Moraea niassensis, a Vulnerable Iridaceae known only from this IPA, Mount Yao is the only known location for an as yet undescribed butterfly species in the genus Baliochila (Congdon & Bayliss 2013). In addition, a species of freshwater crab, Potamonautes bellarussus, described in 2014, is thought to be endemic to the Yao and Mecula inselbergs within Niassa Special Reserve (Daniels et al. 2014). It is possible that the isolated montane habitats created by the inselbergs in the reserve has allowed for the evolution of highly range-restricted species. As the botany of this site is yet to be inventoried, we may expect that more range limited, or even site endemic, species will be documented.
There are a number of sightings of threatened animal taxa around the IPA, including African wild dog (Lycaon pictus - EN), African elephant (Loxodonta africana - VU) and African lion (Panthera leo - VU). However, these species would likely only enter lower altitudes within this IPA and the montane mammalian fauna of this site is yet to be inventoried (van Berkel et al. 2019).

Mount Yao contributes to the tourist experience of Niassa Reserve, as reported by the Mozambican government in a document highlighting the investment opportunities for nature-based tourism potential across the country (ANAC 2018). However, at present the site is not easily accessible for tourists (Luwire Wildlife Conservancy 2019).
For local people, the IPA is likely an important source of water, contributing to 3 different watersheds to the south, north-west and north-east. Yao is also the source of the Chiulezi River, in the lattermost watershed, which serves communities downstream including the villages of Chamba and Matondovela (Luwire Wildlife Conservancy 2019).
Additionally, the lower plains surrounding the inselberg may provide a source of wood for fuel or timber. Elsewhere in the reserve, communities use a wide range of hardwoods but there is no evidence of selective logging of high market value species such as Millettia stuhlmannii and Dalbergia melanoxylon (Timberlake et al. 2004).
Mount Yao shares its name with the Yao ethnic and linguistic group. The waYao (Yao peoples) are thought to have originated from the north of Niassa Province before dispersing through neighbouring areas in the 9th century (Mbalaka 2016). Some sources suggest that the inselberg itself was the nucleus from which the waYao originated. Sacred sites are known from within Niassa Reserve (Wildlife Conservation Society Mozambique, 2021), however, any cultural significance of Mount Yao to local communities has not been documented but could be established through interviews. Greater understanding of how local people interact with the ecosystems within the IPA would better inform conservation and the planning of any future tourist activities.
A number of historically significant examples of cave art are known from Niassa Reserve, dating from tens of thousands of years ago, and it is possible that Mount Yao may also be of archaeological and anthropological importance (Wildlife Conservation Society Mozambique 2021).

Sophie Richards, Royal Botanic Gardens, Kew

Iain Darbyshire, Royal Botanic Gardens, Kew