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Okavango Delta

Date de soumission : 18/03/2016
Critères: (vii)(ix)(x)
Catégorie : Naturel
Soumis par :
Namibia National Commission for UNESCO
État, province ou région :
Kavango East and Zambezi Regions
Ref.: 6098
Transnationale
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Description

This delta system in Kalahari Desert comprises permanent marshlands and seasonally flooded plains. It is one of the very few major interior delta systems that do not flow into a sea or ocean, with a wetland system that is almost intact. One of the unique characteristics of the property is the progressive annual flooding from the River Okavango that progress through the system to reach its peak in Botswana during the dry season, with the result that the native plants and animals have synchronized their biological cycles with these seasonal rains and floods. The biota has uniquely adapted their growth and reproductive behaviour, particularly the flooded grassland biota, to be timed with the arrival of floodwater. It is an exceptional example of the interaction between climatic, hydrological and biological processes. The Okavango Delta is home to some of the world’s most endangered species of large mammal, such as the cheetah, white rhinoceros, black rhinoceros, African wild dog and lion.

Nom(s) de l’élément/des éléments constitutif(s)

Portion of Bwabwata National Park, Nkasa Rupara National Park, Kavango East and Zambezi Regions, S18°12’ E21°42’ and S18°23’ E23°37’

Description de l’élément/des éléments constitutif(s)

One part (87300 ha, 873 km2) is a portion of the Bwabwata National Park in the Kavango East Region along the border between Namibia and Botswana and contiguous with the northern boundary of the inscribed Okavango Delta. Relevant portions include the Mahango and Buffalo Core Conservation areas of the Bwabwata National Park, separated only by the width of the Okavango River. It includes a Ramsar site and extensive areas of deciduous Kalahari woodland. The whole area is protected under Namibian legislation as the Bwabwata National Park since 2007, with one part proclaimed as the Caprivi Game Reserve in 1966 and the Mahango portion proclaimed in 1986.

The Nkasa Rupara National Park (31800 ha, 318 km2) is located in the south-western corner of the Zambezi Region of Namibia along the border between Namibia and Botswana. It is contiguous with the northeastern boundary of the inscribed Okavango Delta property. The area consists of a complex network of waterfilled channels, reed beds, lakes and islands that constitute the Linyanti swamps at the terminus of the Kwando/Linyanti Rivers and the source area for the Chobe River. It is protected under Namibian legislation since 1990 as the Mamili Game Reserve before being renamed as the Nkasa Rupara National Park in 2012.

Justification de la Valeur Universelle Exceptionelle

The Okavango Delta is one of a very few large inland delta systems without an outlet to the sea, known as an endorheic delta, its waters drain instead into the desert sands of the Kalahari Basin. It includes Africa’s third largest alluvial fan and the continent’s largest endorheic delta. These delta systems comprise permanent marshlands and seasonally flooded plains. Furthermore it is in a near pristine state being a largely untransformed wetland system. One of the unique characteristics of the site is that the annual flooding from the River Okavango and associated rivers progressively inundate the wetland systems into the dry season, with the result that the native plants and animals have synchronized their biological cycles with these seasonal rains and floods.

The Delta’s dynamic geomorphological history has a major effect on the hydrology, determining water flow direction, inundation and dehydration of large areas within the system. The site is an outstanding example of the interplay between climatic, geomorphological, hydrological, and biological processes that drive and shape the system and of the manner in which the Okavango Delta’s plants and animals have adapted their lifecycles to the annual cycle of rains and flooding. Subsurface precipitation of calcite and amorphous silica is an important process in creating islands and habitat gradients that support diverse terrestrial and aquatic biota within a wide range of ecological niches.

Criterion (vii): Permanent crystal clear waters and dissolved nutrients transform the otherwise dry Kalahari Desert habitat into a scenic landscape of exceptional and rare beauty, and sustain an ecosystem of remarkable habitat and species diversity, thereby maintaining its ecological resilience and amazing natural phenomena. The annual flood-tide, which pulses through the wetland system every year, revitalizes ecosystems and is a critical life-force during the peak of the Botswana’s dry season (June/July). The Okavango Delta World Heritage property displays an extraordinary juxtaposition of a vibrant wetland in an arid landscape and the miraculous transformation of huge sandy, dry and brown depressions by seasonal floods triggers spectacular wildlife displays: large herds of African Elephant, Buffalo, Red Lechwe, Zebra and other large animals splashing, playing, and drinking the clear waters of the Okavango having survived their long migration across the Kalahari Desert.

Criterion (ix): The Okavango Delta World Heritage property is an outstanding example of the complexity, inter-dependence and interplay of climatic, geo-morphological, hydrological, and biological processes. The continuous transformation of geomorphic features such as islands, channels, river banks, flood plains, oxbow lakes and lagoons in turn influences the abiotic and biotic dynamics of the Delta including dryland grasslands and woodland habitats. The property exemplifies a number of ecological processes related to flood inundation, channelization, nutrient cycling and the associated biological processes of breeding, growth, migration, colonization and plant succession. These ecological processes provide a scientific benchmark to compare similar and human-impacted systems elsewhere and give insight into the long-term evolution of such wetland systems. 

Criterion (x): The Okavango Delta World Heritage property sustains robust populations of some of the world’s most endangered large mammals such as Cheetah, white and black Rhinoceros, Wild Dog and Lion, all adapted to living in this wetland system. The Delta’s habitats are species rich with 1061 plants (belonging to 134 families and 530 genera), 89 fish, 64 reptiles, 482 species of birds and 130 species of mammals. The natural habitats of the nominated area are diverse and include permanent and seasonal rivers and lagoons, permanent swamps, seasonal and occasionally flooded grasslands, riparian forest, dry deciduous woodlands, and island communities. Each of these habitats has a distinct species composition comprising all the major classes of aquatic organisms, reptiles, birds and mammals. The Okavango Delta is further recognized as an Important Bird Area, harbouring 24 species of globally threatened birds, including among others, six species of Vulture, the Southern Ground-Hornbill, Wattled Crane and Slaty Egret. Thirty-three species of water birds occur in the Okavango Delta in numbers that exceed 0.5% of their global or regional population. Finally Botswana supports the world’s largest population of elephants, numbering around 130,000: the Okavango Delta is the core area for this species’ survival.

Déclarations d’authenticité et/ou d’intégrité

The property covers most of the Delta, encompassing a vast area of over 2.14 millions ha of substantially undisturbed wetlands and seasonally flooded grasslands. It is of sufficient size to represent all of the delta’s main biophysical processes and features and support its communities of plant and animal species. Because of its vast size and difficult access the delta has never been subject to significant development and it remains in an almost pristine condition. Tourism to the inner Delta is limited to small, temporary tented camps with access by air. Facilities are carefully monitored for compliance with environmental standards and have minimal ecological impact. Most importantly, the source of the Okavango Delta’s waters in Angola and Namibia remain unaffected by any upstream dams or significant water abstraction and the three riparian states have established a protocol under the Permanent Okavango River Basin Water Commission (OKACOM) for the sustainable management of the entire river system. OKACOM has formally supported the inscription of the Okavango Delta on the World Heritage List. It is imperative that upstream environmental water flows remain unimpeded and that over abstraction of water, the building of dams and the development of agricultural irrigation systems do not impact on the sensitive hydrology of the property.

Conservation management of the Namibian parts are coordinated in accordance with a Strategic Management Plan for Namibia’s North-East Parks that includes close cooperation and coordination with indigenous communities. Local communities and community game guards participate in the management of the Bwabwata National Park component through a technical committee and the Kyaramacan Association, while the northern border of the Nkasa Rupara National Park abuts the Balyewa, Wuparo and Dzoti communal area conservancies. Tourism activities and associated developments are carefully assessed and planned in terms of a Tourism Development Plans to retain the natural balance of these wetland eco-regions.

Justification de la sélection de l’élément/des éléments constitutif(s) en relation avec la future proposition d’inscription dans son ensemble

The Namibian components are contiguous with the inscribed Okavango Delta property. They also form part of the Kavango-Zambezi (KAZA) Transfrontier Conservation Area, which is a five-country initiative that involves Namibia, Botswana, Zambia, Zimbabwe and Angola through a web of 22 protected areas that broadens the regional protected areas network to increase biodiversity and expanding historical game migration routes.

The Bwabwata National Park component shall include the Mahango and Buffalo Core Conservation areas (244 km2 and 629 km2 respectively. These core conservation areas encompass the upper component of the Okavango Delta panhandle, which is a critical component of the wetland system as it is the first areas to be inundated during the important warm summer months of the seasonal flooding cycle. The summer period is a critical period for fish, a multitude of invertebrates and other aquatic and semi-aquatic fauna that require shallow floodplain conditions to breed, as well as the birds, mammals and reptiles requiring that bounty during summer for their own propagation. As the flood waters recede in the shallow upper parts and progressively inundate parts of the Okavango Delta system downstream, juveniles migrating along with the floodwaters to mature continue to support the intricate ecological interactions of the system. Once the lower parts of the Delta in Botswana start drying out after the winter, breeding adults migrate back upstream before a new breeding season commences during summer. In addition, the extensive deciduous Kalahari woodland adjacent to the river accommodates healthy populations of large herbivores, along with associated predators, to move to and from the river. Some 869 species of plants from 88 families, including majestic baobabs, Zambezi teak and African teak occur in the mature and undisturbed riparian and Kalahari woodlands. In addition, 71 species of fish, 5 amphibian species, >100 mammal species and around 450 bird species have been recorded here.

The Nkasa Rupara National Park is Namibia’s mini Okavango Delta and is the largest protected wetland area in Namibia. Ecological processes in the Nkasa Rupara wetlands mirror that of the larger Okavango Delta by being flooded by the Kwando/Linyanti Rivers during the wet summer months. However, due to its small size the seasonal floods progress fairly rapidly through the system, resulting as much as 80% of the park becoming inundated by water and inaccessible during the wet season before discharging as the Chobe River. During this period it serves as an important secluded breeding area for birds, fish, invertebrates and other resident animals, with herds of elephant, buffalo and other animals freely migrating from the Okavango Delta and converging from adjacent areas in Botswana to feed on the lush vegetation. Even during the dry season the pools, channels and marshy areas abound with fish, crocodiles, hippopotamus, red lechwe, reedbuck and birds (~450 species recorded). These wetlands are a central component in the historical migration routes of animals such as elephants and buffalo that links populations in Angola and Zambia with those in Botswana and Zimbabwe.

Comparaison avec d’autres biens similaires

The Okavango Delta was inscribed on the World Heritage List in 2014. The parts in Namibia extend the inscribed area to include small but important areas to maintain the ecological functioning and integrity of the inscribed area.