Nakai – Nam Theun National Park (NNT NP)

North: 105° 09'37.3"E; 18°23'21.3"N
East: 105° 38'36.4"E; 17°59'18.4"N
South: 105° 25'30.7"E; 17°35'24.9"N
West: 105° 47'21.4"E; 18°01'48.4"N

Nakai – Nam Theun National Park (NNT NP) including two corridors with two other neighbouring protected areas (Hin Nam No National Park to the south and Phou Hin Poun National Park to the west), is located in east central Lao PDR along the international border with Viet Nam and is one of the country’s largest and most ecologically significant protected areas. Covering approximately 4,700 square kilometers, it is one of the original National Biodiversity Conservation Areas (now called National Protected Areas) of Lao PDR established in 1993 by Prime Minister Decree 164. National Park, including the watershed area of the Nam Theun 2 Hydropower Project, was established in 2019 under Decree 36/PM. The national park forms a core part of the Annamite Mountains ecoregion, known globally for its high biodiversity, exceptional levels of endemism, and critical ecosystem services. The park spans a diverse range of habitats from lowland evergreen and semi-evergreen forests to high-elevation cloud forests and wetlands supporting a remarkable assemblage of species, including some of the world’s rarest mammals, birds, and plants and several endemic species to the Annamite Mountain range.

NNT NP is one of the largest remaining contiguous areas of mostly primary forest in the ‘Indo-Burma Hotspot’ (comprising Cambodia, Lao PDR, Myanmar, Thailand, Viet Nam and parts of southern China). The Indo-Burma Hotspot is ranked in the top 10 global hotspots for irreplaceability and in the top five for threats (Mittermeier et al. 2004; Conservation International, 2011). This hotspot contains the third highest number of vertebrate species and one of the highest levels of vertebrate endemism in the world.  NNT NP is one of the identified ‘Key Biodiversity Areas’ within the Indo-Burma hotspot (Tordoff et al., 2012). In Lao PDR, NNT NP is ranked as one of the most important areas for biodiversity conservation at the national and global levels. Although (as for every other large, complex, natural area in Indo-Burma) there is no comprehensive biodiversity census for the area, but early surveys have identified at least 92 mammal species, 403 bird species, 29 reptile species, 69 fish species, 25 amphibian species, and 917 species of Non-Timber Forest Products (Timmins and Evans, 1996; Dersu & Associates., 2008; Robichaud and Stuart, 1999).

The Outstanding Universal Value of Nakai – Nam Theun National Park (NNT NP) is justified by the fact that it is located within the Annamite Mountains: a unique ecosystem with a high level of endemism and that there are no other properties with World Heritage status with the particularities of NNT NP’s ecosystem within this unique ecosystem.

The Annamite Mountains extend from northern Viet Nam along the border with Lao PDR and south into southern Viet Nam. It is recognised as a priority for biodiversity conservation by the ‘WWF Global 200 Ecoregions’ (Olson and Dinerstein, 2002). The region has a complex geological history; successive periods of sedimentation over millions of years formed an enlarged stable block of complex geological forms, including ancient rocks, limestone karst, and volcanic regions. The Annamite Mountains range forms an important barrier between Viet Nam’s moist uplands and the drier monsoon ranges of Lao PDR, resulting in divergent weather patterns across the range. It is believed that the Annamite Mountains have provided stable refugia for plant and animal species during climatic glaciations of the Pleistocene era, which are likely to have resulted in speciation and the high level of endemism observed today in this region. Various explorations in the 1990s penetrated areas poorly covered before and resulted in remarkable discoveries of large mammal species new to science, specifically concentrated within the Annamite Mountains. These new discoveries included the Saola Pseudoryx nghetinhensis, the Large-antlered Muntjac Muntiacus vuquangensis, the Annamite Muntjac M. truongsonensis and the Annamite Striped Rabbit Nesolagus timminsi.

Criterion (ix): NNT NP encompasses a variety of different forest types for the diversity of species found in the areas. The most common forest type is dry evergreen forest found between 500 to 1800 m above sea level (a.s.l.). Other more localised forest types include the semi-evergreen/pine forest, wet evergreen forest close to the Viet Nam border over 600 m a.s.l., and upper montane forest at the highest elevations from 1800 m a.s.l. (Timmins and Evans, 1996). Elevation in the area ranges from ca. 500 m to 2300 m a.s.l. Measured annual precipitation ranges from 1865–2620 mm but may be considerably higher in some of the wettest areas. Monthly mean temperatures range 14–24°C, with annual extremes of 4 to 32 °C. The area typically experiences four seasons based on average monthly rainfall and temperatures: a cold dry season in December– February, a warm dry season in March–May, a warm wet season in June–September, and a further warm dry season in October–November. This variety in forest types, topography and seasonal patterns explain its diversity in flora and fauna.

In terms of fauna, the characteristic and remarkable rare and locally endemic faunal species of the Annamite Mountains are found in the NNT NP, including the Saola, Large-antlered Muntjac, Roosevelts’-group muntjac(s) (a group which comprises several species, includes the Annamite Muntjac, which are difficult to tell apart), Annamite Stripped Rabbit, and Owston’s Civet. These species are representatives of Evolutionarily Distinct and Globally Endangered (EDGE) Species.

The World Heritage List currently underrepresents sites with critical habitats for EDGE species, species that are both highly evolutionarily distinct and at risk of extinction. NNT NP is home to several such species.

In addition, a large number of Globally Threatened (i.e. Vulnerable [VU], Endangered [EN] and Critically Endangered [CR]) and Near Threatened (NT) species (as listed in the IUCN Red List of Threatened Species; IUCN 2025) and/or locally endemic mammals are recorded in NNT NP such as VU Sambar (Rusa unicolor), NT Mainland Serow (Capricornis sumatraensis), CR Sunda Pangolin (Manis javanica), EN Hatinh Langur (Trachypithecus hatinhensis), EN Pygmy Slow Loris (Nycticebus pymaeus), EN Bengal Slow Loris (Nycticebus bengalensis), VU Asiatic Black Bear (Ursus Thibetanus), VU Sun Bear (Helarctos malayanus), VU Binturong (Arctictis binturong), VU Hog Badger (Arctonyx collaris), VU Great Hornbill (Buceros bicornis), VU Roufous-necked Hornbill (Aceros nipalensis), NT Brown Hornbill (Anorrhinus austeni), CR Indochinese Box Turtle (Cuora galbinifrons), VU Impressed Turtoise (Manouria impressa), VU Southeast Asian Box Turtle (Cuora amboinensis), EN Keeled Box Turtle (Cuora mouhotii)., though some are likely to have gone extinct in the past two-three decades.

NNT NP has notably been distinguished as an important area for the conservation of small carnivores (Coudrat et al., 2014), Eurasian and Asian small-clawed otters (Coudrat et al., 2022), Red-shanked Douc (Coudrat et al., 2012; Coudrat et al., 2013), macaques (Coudrat & Nekaris, 2013), Northern and Southern White-cheeked gibbons (Coudrat et al., 2015; Coudrat et al., 2025), muntjacs (Alexiou et al., 2021), elephants (Ahlering et al., 2011; Budd et al., 2023). Less recent information is available on reptiles, amphibians and birds; however, several species known to occur in NNT NP are Globally Threatened and of global, regional and/or national conservation significance (Thewlis et al. 1998; Robichaud and Stuart, 1999; Stuart et al., 2010; Stuart et al., 2011; Timmins & Evans, 1996). Previous research on fish diversity and fisheries have been conducted, mostly focusing on the Nam Theun Reservoir and Nam Theun River. The Nam Theun River showed a large proportion of endemic species (Kottelat, 2016). Cypriniformes is the largest group in terms of species but also in abundance; the Siluriformes is the second group of species represented (Gillet et al., 2018; Cottet et al., 2016; Cottet et al., 2017).

In term of flora, from the limited botanical surveys conducted within the Annamite Mountains, plant biodiversity is exceptionally rich, comprising notably recent discoveries of new species of orchids and other endemic species of conifers (Coffman, 2021). However, the flora of Lao PDR remains one of the least studied in the region (Newman et al., 2007a), consistent with the paucity of botanical work that has been conducted in NNT NP. The most comprehensive botanical surveys conducted in the area date from specimens collected between 2004 and 2007 (Newman et al., 2007b) which resulted in 614 identified species (in 527 genera and 143 families). The authors of the work and compilers of the documents recognize that ‘this is only a small fraction of the number of species that are present’ (Newman et al., 2007a: 1) but this preliminary work identified 34 species that are of at least national conservation concern (Thomas et al., 2007).

Criterion (x): Recent camera-trap surveys (Coudrat, 2019; Coudrat 2020; Coudrat, 2023) notably shows that NNT NP holds globally important populations of several species Annamite endemics, notably the Endangered Owston’s civet, the Critically Endangered Large-antlered Muntjac (Muntiacus vuquangensis) and Data Deficient Annamite dark muntjac species complex (Muntiacus rooseveltorum/truongsonensis). These threatened endemics have become extirpated across much of their historic range, with the Large-antlered Muntjac now approaching global extinction, and NNT NP is one of their best hopes for long term survival. The diversity and detection rates of several other species recorded by camera-traps in recent years in NNT NP also shows that the faunal community in NNT NP is much less defaunated than other Annamite forests that have been surveyed in recent years (Alexiou et al., 2024; Alexiou et al., 2022). In addition to healthy populations of several ground-dwelling species, NNT NP holds one of the largest populations of Critically Endangered White-cheeked Gibbon (Nomascus siki/N. leucogenys) (Coudrat, 2021; Coudrat et al., 2025) and Critically Endangered Red-shanked Douc (Pygathrix nemaeus) (Coudrat et al., 2012; Coudrat et al., 2013). NNT NP also represents an important area for the long-term survival of the Vulnerable Asian Small-clawed Otter (Aonyx cinereus) and the Near Threatened Eurasian Otter (Lutra lutra) (Coudrat et al., 2022). 

The entire population of the Critically Endangered Asian Swamp Cypress known in Lao PDR is within the NNT NP, excepting one small stand just to the northwest. This makes the area a priority for the global conservation of this species (Coffman, 2021).

Recent research shows that the largest global population of Endangered Wolf Barb Luciocyprinus striolatus (Paa Kang) and best chance for long-term survival is found in NNT NP (Ounboundisane et al., 2023). In addition to this species NNT NP holds significant populations of other globally important species, including Tor ater, Scaphognathops theunensis, and Poropuntius carinatus. (Ounboundisane, 2025).

NNT NP exhibits a high degree of integrity in terms of its ecological processes, biodiversity, and natural features. The park encompasses all critical elements necessary to express its Outstanding Universal Value (OUV), as described above and is of adequate size to ensure the long-term conservation of the ecological and evolutionary processes, habitats, and species for which it is being nominated.

The park's boundaries have been carefully delineated to include a comprehensive and contiguous representation of its bio-physical features. These include core habitats of globally significant species,  ecosystems of mostly primary forest, and essential physical formations such as watersheds, mountain ranges, and forested valleys that sustain ecological functions and processes. The area is sufficiently large and cohesive to accommodate natural fluctuations of species populations and habitat dynamics, and to ensure ecosystem resilience in the face of environmental change.

Nakai – Nam Theun National Park remains more forested than does most of the rest of the Annamite Mountains, still containing 88% of its original forest cover. Evergreen forests cover the majority of the NP, including almost the entirety of the Total Protection Zone (93.3%) (Ferrand and Moore, 2018). Most notably NNT NP is divided into management zones including three Biodiversity Priority Zones (BPZs) that were delineated based on their conservation importance at the global levels and past (and current) threat analysis (from past biological and threat records and from expert knowledge). The three zones are Total Protection Zones, meaning that any human activity, with the exception of scientific research and ecotourism, are prohibited. The Nam Chae zone is characterized by lowland (mean elevationof 737 ± 136 m a.s.l.) dry semi-evergreen and coniferous forest types with notably large amounts of bamboo forests less common in other zones. Thong Khouang zone is characterized by steep terrain (mean elevation 803 ± 239 m a.s.l.) with mostly dry evergreen forest with notable sections of large non-kart formations and wetter forest closer to the Vietnamese border.Thong Khacheng zone is in a higher elevation area (mean of 1136± 272 m a.s.l.) dominated by dry evergreen forest.

A recent study (Alexious et al., 2024) focussing on ground-dwelling species highlights the conservation importance of NNT NP for biodiversity. The faunal community in NNT NP appears to be much less defaunated than other Annamite forests that have been surveyed in recent years. From the study a total of 40 mammals were identified: 18 species were listed as ‘Near Threatened’ or above according to the IUCN (2025). Five of these species were Annamite endemics (Annamite Dark Muntjac, Annamite Striped Rabbit, Large-antlered Muntjac, Owston’s Civet and Red-shanked Douc).

The park’s key conservation features—such as endemic and endangered species habitats, migration corridors, and representative ecosystems of the bio-geographic region are mostly intact and functionally interconnected. These include, but are not limited to, dry semi-evergreen forest, montain forest, coniferous forest, bamboo forest, wet evergreen forest, riverine forest and large rivers and a network of streams, which illustrate ongoing ecological and biological processes (criterion ix) and provide habitat for globally threatened species (criterion x), thereby fulfilling integrity conditions specific to those criteria.

NNT NP have faced several threats that demand consistent management attention and strong collaboration with local communities. These include the unsustainable use of natural resources and forest products, biodiversity loss from poaching, which has led to local extinction of some species such as Tiger, land conversion for agriculture. It is crucial that any development initiatives within or near the park’s boundaries are strictly limited, and effectively regulated to ensure they do not compromise the long-term preservation of the property’s Outstanding Universal Value. The park currently offers hope for conserving a significant representation of biodiversity.

NNT NP is governed under 122/PM 2017 (currently in the process of being amended to improve the governance) and 36/PM 2019 which taken together set out the membership and reponsibiltiies of the Nakai - Nam Theun National Park Management Committee, chaired by the Minister of Agriculture and Forestry, and with representation of other relevant ministries, provincial agencies and two district governors. Under this structure, NNT NP is managed by a government institution (the Nakai-Nam Theun National Park Management Division under the Ministry of Agriculture and Forestry) that has and implements a Social and Environmental Management Framework and Operational Plan (SEMFOP). Under this framework, the park implements law enforcement patrols, local communities sustainable development, biodiversity research and monitoring, and community awareness raising. The management of the park under this framework is audited annually by an independant body that reviews activities and funds management. NNT NP is one of the most funded protected areas in the region, receiving annual funds from the Nam Theun 2 Power Company, as an offset for the Nam Theun 2 (NT2) hydropower project in operation since 2010. Therefore, NNT NP must also operate to fulfil the government’s obligations under the NT2 Concession Agreement as they relate to the NT2 watershed area including that each Annual Workplan and Budget must conform to the SEMFOP (NNT NP, 2022).

The vision of NNT NP management is that the Nakai Nam Theun National Park is managed to effectively protect its biodiversity values, maintain and enhance its natural ecosystems, protect its rivers and soils and to improve the livelihood of the inhabitants of the National Park and Peripheral Impact Zones [buffer zone] villages who rely on its resources (NNT NP, 2022). NNT NP also has a Biodiversity Research and Monitoring Strategy completed in 2025 (NNT NP, 2025a). In addition, NNT NP is in the process of applying to be considered under the IUCN Green List of Protected and Conserved Areas, which evaluate four components: (i) good governance, (ii) sound design and planning, (iii) effective management, (iv) successful conservation ourcomes. Together, these stuctures and processes in place provide strong potential for the long-term conservation of integrity of the park (NNT NP, 2025b).