Tana River Delta (6412)
Kenya, Africa

Site overview

KBA status: confirmed

Global KBA criteria: D1a

Year of last assessment: 2004

National site name: Tana River Delta

Central coordinates: Latitude: -2.5000, Longitude: 40.3333

System: marine, terrestrial

Elevation (m): 0 to 37

Area of KBA (km²): 1576.20084

Protected area coverage (%): 1.49

KBA classification: Global

Legacy site: Yes

Site details

Site description: The Tana delta is the name loosely given to the flood-plain ecosystem of the lower Tana river, a vast wetland complex on the Kenyan coast. The delta is roughly triangular in shape, with its apex at Lake Bilisa (north of Garsen) and its base a 50 km stretch of beach along Ungwana (or Formosa) Bay, stretching from Kipini in the north-east to Mto Kilifi in the south-west. This low-lying area is bounded by higher land to the east and west, and to the south by a dune system bordering the Indian Ocean. It forms the interface between the river and the ocean, with fresh and brackish lakes and streams, freshwater and saline grasslands and wetlands, and successional stages of forest and woodland on the riverbanks and the dune ridges parallel to the shore. The mouth of the river has shifted many times. Today, the main stream of the Tana follows an artificial course, directly into an estuary at Kipini, rather than into the complex system of channels and distributaries leading to its old mouth at Mto Tana. Until recently, some fresh water still flowed into the ‘old’ delta through one of these channels, the Kalota Brook. However, since 1988 a small dam has blocked this, built by Pokomo farmers, who use the tidal bore to push fresh water into their fields and irrigate their crops. Alluvial sediments cover the entire flood-plain in the lower parts. Flooding happens as a result of rain in the river’s catchment on Mount Kenya (IBA KE005) and the Aberdare mountains (KE001). Normally, the major floods occur in April–May, with a smaller, short-rains flooding in October–November. The timing, extent and duration of the flooding vary greatly from year to year. The Tana river delta contains a very wide variety of habitats, including riverine forest, grassland, woodland, bushland, lakes, mangroves, dunes, beaches, estuaries and coastal waters. Small fragments of riverine forest, not nearly as extensive as the forests north of Garsen (see KE023), occur along the present or former river courses. Seasonally flooded flood-plain grasslands cover c.67,000 ha of the delta. West of the flood-plain is a diverse bushland. Wooded bushland or grassland, with fire-resistant tree species, occupies a broad swathe east of the flood-plain, merging into the Boni forest vegetation to the north. Other bushland associations form a complex mosaic with the flood-plain grasslands. Parallel to the coast along Ungwana Bay run lines of high dunes, some as much as 37 m above the sea. These are covered by their own distinctive vegetation, a dense thicket dominated by Dombeya sp. and Grewia similis. In the valleys the thicket mingles with taller trees, including various palms. Palms are prominent in many places. In some areas, especially those cleared and burned in the past, these form substantial tracts of palm-bushed grassland. Tall mangrove forest grows at Kipini in the Tana estuary and along the network of channels further south. As well as seasonal wetlands in the oxbows and flood-plain depressions, the delta contains a number of near-permanent lakes and marshes. Some of these may dry out in certain years, but others, like Lake Shakababo and Bilisa, maintain true aquatic plants and good populations of several species of fish. Luo and Luhya immigrants to the area are responsible for an active and thriving fishery, while Orma pastoralists use the wetlands as dry-season grazing areas for their livestock. Fishermen also camp for days or weeks, while catching, salting and drying fish, on the coral outcrops of Mwamba Ziwayuu, c.10 km offshore from Kipini. The other main ethnic group in the area, the Pokomo, are agriculturalists who cultivate a narrow strip on either side of the river, and around the seasonal and permanent wetlands. As the floods start to recede, rice is planted in the shallow water. Several crops of rice follow the water as its level drops, and other crops, such as maize and sweet potatoes, are planted on the drying mud. There is also an irrigation scheme growing rice in traditional style at Ozi, near Kipini, and a much larger, mechanized one upstream, east of Garsen, that is eventually intended to cover as much as 16,000 ha.

Rationale for qualifying as KBA: This site qualifies as a Key Biodiversity Area of international significance that meets the thresholds for at least one criterion described in the Global Standard for the Identification of KBAs. KBA identified in the process of compiling the 2003 CEPF Ecosystem Profile of the Eastern Arc Mountains and Coastal Forests Hotspot (which was later [in 2005] split into two Hotspots, the East Afromontane and the Coastal Forests of Eastern Africa). Species taxonomy and threat category was based on IUCN Red List 2002.

Additional biodiversity: See Box and Table 3 for key species. The Tana river delta is a stronghold for two Near Threatened, restricted-range species, Anthus melindae and Acrocephalus griseldis (probably its main wintering ground). Circaetus fasciolatus is uncommon in riverine forest, but has not been recorded in recent surveys. The wetlands, including the coastline and offshore islets, at times hold exceptional concentrations of waterbirds. Internationally important populations have been recorded here for no fewer than 22 species, making the delta one of the key sites in the country for waterbird conservation. The Tana delta also supports one of the very few breeding sites for colonial waterbirds in Kenya. This heronry is near Idsowe, south of Garsen, on Ziwa la Matomba, a seasonally-flooded lagoon where the birds nest in a thicket of Terminalia brevipes, usually between May and September but also at other times if the lagoon is flooded. Up to 5,000 colonial waterbirds of at least 13 species have been recorded nesting here, including Anhinga rufa (up to 100 pairs), Ardea cinerea, A. purpurea, Egretta ardesiaca, Ardeola ralloides and Nycticorax nycticorax, Casmerodius albus, Mesophoyx intermedia and Egretta garzetta, Anastomus lamelligerus, Threskiornis aethiopicus and Plegadis falcinellus, and Platalea alba. Mwamba Ziwayuu, a small coral platform offshore from the Tana estuary, is a resting site for significant numbers of Sterna saundersi and S. bengalensis that feed in Ungwana Bay. Regionally threatened species include Casmerodius albus; Ephippiorhynchus senegalensis (a regular visitor in small numbers, May to September) and Turdoides squamulatus (local and uncommon). Non-bird biodiversity: The importance of the Tana river delta lies in the expanse, intactness, variety and productivity of its habitats. The flood-plain is grazed by a number of ungulates, including the restricted East African coast subspecies of the ungulate Damaliscus lunatus topi, with some 30,000 or so in the area. The rivers and channels support large numbers of Hippopotamus amphibius (estimated at 400–450) and Crocodylus niloticus. Ungwana Bay is one of the few places where Dugong dugon (VU), critically endangered in the region, has been recorded recently. The turtles Chelonia mydas (EN), Eretmochelys imbricata (CR) and Lepidochelys olivacea (EN) nest on the sandy beaches. Twenty-two freshwater fish species are recorded from the lower Tana, including three eels Anguilla spp. and a distinct subspecies of Petrocephalus catastoma. The mangroves provide vitally important spawning and nursery grounds for many species of fish and crustaceans. The extensive mangrove forests include the only significant stands in Kenya of the plant Heriteria littoralis, and two other plant species that are considered threatened Xylocarpus granatum and Bruguiera gymnorrhiza. At least 280 plant taxa are recorded for the delta, and many more undoubtedly occur as there has been no thorough botanical survey; of these, 18 are considered rare in Kenya or globally.

Delineation rationale: Type 2 marine IBA: non-breeding (coastal) congregations.

Habitats

Land use: agriculture | fisheries/aquaculture

IUCN Habitat	Coverage %	Habitat detail
Marine Coastal/Supratidal	9
Forest	5
Artificial - Terrestrial	9
Shrubland	9
Grassland	50
Wetlands(Inland)	9
Marine Intertidal	5
Marine Neritic	5

Threats

Summary of threats to biodiversity at KBA: Disputes over the rights to water and land are at the heart of the complex conservation problems facing the Tana river delta. The importance of the area for conservation is widely recognized, but there is little agreement on the appropriate steps forward, and the site remains without any formal protection. The numerous patches of riverine habitat in the delta are edaphic in origin, and their continued existence depends on critical minimum levels of flooding. The flood regime has already been disrupted by five large water impoundments upstream (including Masinga Reservoir, IBA KE030). A proposed new pair of dams to be built by the Mutonga-Grand Falls Hydropower Project has the potential for even more serious impacts. Environmental impact assessment suggested that the new dams would greatly reduce river discharge, silt deposition and the level of groundwater. However, the present design of the Low Grand Falls dam incorporates an artificial flood and sediment release facility. This is intended to release sediments and artificial floods twice a year. Mutonga Dam will also have sand-flushing facilities. It remains to be seen how effective these measures will be. The Tana and Athi Rivers Development Authority have initiated a major rice irrigation scheme in the Tana delta, with funding from the Japanese Government. Four thousand hectares are presently under production near Garsen, and the scheme is creating considerable employment. It has also damaged riverine forest and, if expanded to the planned 16,000 ha, will convert a large swathe of traditional dry-season grazing land relied upon by pastoralists. The ecological impact study by Ecosystems Ltd. (1985) strongly recommended reassessment of the whole project concept, pointing out that there were more efficient ways of producing rice and much more appropriate ways of using the delta’s resources than monopolising them for a single agricultural activity. Other smaller projects have similarly severely impacted the natural flooding patterns. There has been a long-running debate over land ownership and tenure within the delta that has had knock-on effects for conservation and development initiatives in the area. In the continuing state of confusion, environmental degradation in this (until recently) pristine habitat continues apace. Destruction of woodland and mangroves, slash-and-burn agriculture, illegal hunting of wildlife and unregulated offshore trawling are all diminishing the delta’s resources. More disturbingly, there are reports of allocations of large chunks of land to senior government officials and civic leaders from the district. The local communities remain hostile to ideas of their ancestral land being hived off as a wildlife reserve (as has been proposed by the Kenya Wildlife Service). Ironically, protection under the Ramsar Convention means something quite different to this. The Convention enshrines the idea of wise use—and central to this is that the needs of the local people must be met, in a sustainable way. The resources of the delta are bountiful enough that it can be managed in the interests of those who live there, while ensuring the long-term conservation of its birds and other biodiversity. The sooner the planning process begins the better.

Threat level 1	Threat level 2	Threat level 3	Timing
Agriculture & aquaculture	Annual & perennial non-timber crops	Small-holder farming	Ongoing
Agriculture & aquaculture	Livestock farming & ranching	Nomadic grazing	Ongoing
Biological resource use	Logging & wood harvesting	Intentional use: subsistence/small scale (species being assessed is the target) [harvest]	Ongoing
Natural system modifications	Dams & water management/use	Abstraction of surface water (commercial use)	Ongoing
Invasive & other problematic species, genes & diseases	Invasive non-native/alien species/diseases	Named species	Ongoing
Residential & commercial development	Housing & urban areas		Ongoing
Residential & commercial development	Tourism & recreation areas		Ongoing
Transportation & service corridors	Roads & railroads		Ongoing
Human intrusions & disturbance	Recreational activities		Ongoing
Climate change & severe weather	Habitat shifting & alteration		Ongoing
Climate change & severe weather	Droughts		Only in the future
Climate change & severe weather	Storms & flooding		Only in the future
Pollution	Garbage & solid waste		Ongoing

Additional information