Location and General Description
The Nile Delta Flooded Savanna ecoregion extends along the River Nile from the Aswan High Dam, 1,100 km downstream to the mouth of the Nile as it enters the Mediterranean Sea. The delta is about 175 km long and 260 km wide (Hughes and Hughes 1992). Since the construction of the Aswan High Dam, the riverine floodplains and delta are no longer subject to annual flooding, and Cyperus papyrus swamps that used to exist in the wettest areas have largely disappeared. The remaining marshland is associated with lakes and lagoons along the seaward face of the delta. Outer margins of the delta are eroding, and salinity levels of some of the coastal lagoons are rising as their connection to the sea increases.
The Nile is the longest river in the world, extending 6,695 km from the mountains on the eastern side of Lake Tanganyika to the Mediterranean Sea, with an estimated basin area of 3,026,000 km2. The main tributaries to the Nile are the Bahr el Jebel, the Bahr el Ghazal and the Sobat River, which combine and become the White Nile, as well as the Blue Nile and the Atbara River. This ecoregion only covers the Nile downstream from the Aswan High Dam, where peak floods in September yield a flow rate of 8,100 m3/sec. Approximately 84 percent of the water reaching Aswan comes from the Ethiopian Highlands and 16 percent from Equatorial East Africa. After the high dam, as the river continues downstream, it receives numerous ephemeral tributaries from the western hills that separate the Nile from the Gulf of Suez. These periodic rivers are dry most of the year, but torrents flow down the water-worn gullies after heavy winter rainstorms in the hills (Hughes and Hughes 1992).
The Nile River previously braided into many channels as it flowed through the 26,000 km2 delta, depositing and moving unconsolidated, alluvial sediments brought from upper reaches of the river. However, flow levels have been greatly reduced since construction of the dam, and now the river occupies only two main channels, while several lakes occupy former channels of the river. The mean rate of discharge, measured above the delta, is 820 m3/sec. The Nile divides into two below Cairo, into western and eastern branches that flow into the sea at Rosetta and Damietta, respectively. The main lakes in the delta are El Mannah, El Qatta, Faraontya, Sinnéra, Sanel Hagar and there are two coastal lagoons, Manzala and Miheishar.
The delta experiences a Mediterranean climate, with summer temperatures at a maximum in July and August (mean 30oC, max. 48oC) and winter temperatures of 5o to 10oC. Only 100 mm to 200 mm of rain falls each year in the Nile Delta Flooded Savanna ecoregion, and this small amount is concentrated in the winter. Farther south, in the vast Saharan Desert, the Nile River is a vital lifeline for the people who live in this arid, hot region.
The Nile Delta was once known for large papyrus (Cyperus papyrus) swamps, but papyrus is now largely absent from the delta. Vegetation consists of Phragmites australis, Typha capensis, and Juncus maritimus, with some small sedges. The large Manzala coastal lagoon supports beds of Ceratophyllum demersum, Potamogeton crispus, and P. pectinatus around the southern shore as well as dense phytoplankton. Other typical species found here are Najas pectinata, Eichhornia crassipes, and Cyperus and Juncus spp. that grow along lake shores (Hughes and Hughes 1992). The salt tolerant Halocnemum spp. and Nitraria retusa grow in marshes along the Mediterranean coast. Farther south along the river, dense swamp vegetation grows unchecked without the seasonal fluctuations of the Nile, held back by the Aswan Dam. Phragmites and Typha grow along riverbanks that were previously bare. The islands along the river, especially those found between Luxor and Kom Ombo, hold reed swamp vegetation that is attractive to waterfowl (Baha El Din 1999).
The Nile Delta is part of one of the world’s most important migration routes for birds. Every year, millions of birds pass between Europe and Africa along the ‘eastern African flyway’, and the wetland areas of Egypt are especially key as stopover sites (Denny 1991). Species that pass through the Nile Delta Flooded Savanna ecoregion include white stork (Ciconia ciconia), black stork (Ciconia nigra), European crane (Grus grus) and white pelican (Pelecanus onocrotalus), as well as numerous birds of prey, including short-toed eagle (Circaetus gallicus), booted eagle (Hieraaetus pennatus), steppe eagle (Aquila nipalensis), lesser spotted eagle (Aquila pomarina), steppe buzzard (Buteo buteo), honey buzzard (Pernis apivorus) and levant sparrowhawk (Accipter brevipes). Large numbers and a wide diversity of waterbirds, passerines and other bird groups also pass through the country during the spring and autumn.
Several hundred thousand waterbirds winter here in the Delta, including the world’s largest concentrations of little gull (Larus minutus) and whiskered tern (Chlidonias hybrida) in Lake Manzala (Baha El Din, 1999). Other waterbirds include shoveler (Anas clypeata), teal (A. crecca), wigeon (A. penelope), garganey (A. querquedula), grey heron (Ardea cinerea), pochard (Aythya ferina), ferruginous duck (A. nyroca), Kentish plover (Charadrius alexandrinus), and cormorant (Phalacrocorax carbo) (Hughes and Hughes, 1992). This ecoregion contains the largest breeding population of slender-billed gull (Larus genei) in the Mediterranean Sea.
The Nile has been connected to the Niger and Chad water systems at various times in the late Pleistocene, through a series of shallow lakes in the Sahara Desert. Therefore, the three river systems share a similar flora and fauna, and endemism in the Nile is low (Kingdon 1989). The delta is rich in wetland plant species that grow in the remaining freshwater wetlands and coastal strip. The Nile River within Egypt has at least 553 plant species associated with it, of which at least 8 species are endemic. Two additional endemics live in the oases close to the Nile (El Hadidi and Hosni, 1994). A member of the white-toothed shrew genus, Crocidura floweri, is also endemic to the ecoregion. European mammals found here include the otter (Lutra lutra) and the red fox (Vulpes vulpes). Healthy populations of swamp cat (Felis chaus) can be found around Lake Manzala. The hippopotamus (Hippopotamus amphibius) became rare in the 18th century, with the last known individual in Egypt killed around 1816.
The ecoregion provides habitat for one endemic frog, Bufo kassasii. Aquatic reptiles include Varanus niloticus and Crocodylus niloticus as well as two marine turtles which breed at Lake Bardawil in the Delta, the endangered loggerhead (Caretta caretta) and the endangered green turtle (Chelonia mydas). The African softshell turtle (Trionyx triunguis) was once found in the Delta but has been eradicated from Egypt. The remaining Mediterranean population is considered to be critically endangered (Schleich et al.1996). The endangered Egyptian tortoise, Testudo kleinmanni, lives in the dunes and islets of this ecoregion. Marine fish are found in the delta, such as Anguilla spp., Mugil cephalus and Solea vulgaris. Financially important species in the lakes and lagoons include Oreochromis niloticus, O. aureus, O. galilaeus, Tilapia zillii and Clarias spp. (Hughes and Hughes 1992).
Practically no areas of delta habitat remain undisturbed. The completion of the first Aswan Dam (between 1912 and 1934) dampened the annual flood pulse in the Nile Delta. The completion of the second Aswan (High) Dam totally stopped flooding and most of the former seasonally or permanently flooded habitats have subsequently been converted to settled agriculture. Before the dams were built, floodplain farming had occurred for over 5,000 years, although flooded areas were only farmed after the flood receded. However, since the closure of Aswan Dam, floodplains are farmed year-round, causing the loss of much of the wetland habitats of the delta and lower Nile River floodplain. Only fragments of the former wetlands remain. The best remaining habitat is found in the Lakes El Mannah, El Qatta, Faraontya, Sinnéra, Sanel Hagar and the coastal lagoons of Manzala and Miheishar.
The ecoregion is largely unprotected. Ashtoun el Gamil-Tanee Island Natural Area and the Lake Burullus Ramsar site are the only two protected areas in the delta and cover a total area of less than 500 km2. Lake Burullus is threatened by fishing and pollution although it remains the most unspoiled of the delta wetlands. Ashtoun El Gamil Protected Area was created largely to protect gravid fish and fry as they journey in and out of nearby Manzala Lake, and is not large enough to contain any suitable waterfowl habitat. There are plans to enlarge this protected area, which may give it a greater significance in the conservation of Egypt’s resident and transient avifauna (Baha El Din, 1999).
Types and Severity of Threats
Virtually all of the 63 million people of Egypt live in the Nile Delta Flooded Savanna ecoregion. Population densities average 1,000 persons/km2 with much higher densities occurring in major towns (e.g. Cairo). Population pressure on natural resources is consequently immense, and humans have altered all of the natural vegetation outside of small reserves. People arrived in the area around 250,000 years ago and have been farming intensively here for more than 5,000 years.
The delta ecosystem no longer receives a yearly input of sediments and nutrients from upstream. Consequently, the soils of the floodplains are poor and large amounts of fertilizers are applied to the land each year. Run-off of fertilizers and dumping of wastewater and sewage sludge is leading to the accumulation of trace elements in the sediments of the delta (Elsokkary 1996). At least one species, the catfish Clarias lazera, has been shown to be accumulating metals, including mercury, iron and copper in its muscle and liver (Adham et al 1999). Fertilizers, along with salt-water intrusion, have also caused the upper delta to become more saline. Pesticides such as DDT and Lindane have been detected in at least one of the lakes (Hughes and Hughes 1992).
There are three major threats to the remaining habitats and species. Salinity may continue to increase in the delta from infiltration by seawaters as the delta face erodes and as erosion opens the existing lagoons to the sea. Wetlands and other migrating birds will increasingly be hunted and trapped to provide a food source for local populations, and for sale to other countries (e.g. quail trapping which occurs along the coast). Finally, inappropriate siting of windmills for electricity generation could cause considerable mortality in migrating birds.
Other concerns include rising sea levels due to changing global climatic conditions. For example, El-Raey et al. (1997) estimate that with only a half-meter rise in sea level, 26 percent of the city of Rosetta and the estuary of the River Nile would be inundated. Ongoing efforts to halt erosion along the Nile banks by lining them with rocks will likely make these areas less attractive to waterfowl (Baha El Din, 1999). In addition, political conflicts between upstream and downstream countries could intensify. Egypt is totally dependent on the Nile River and uses its considerable regional power to prevent upstream countries from developing water use schemes that threaten its water supply (Singh et al 1999).
Justification of Ecoregion Delineation
Although there is no comparable vegetation unit covering this area (White 1983), expert opinion delineate the mouth of the Nile Delta and an area running along the Nile River as a separate ecoregion. The boundary of the ecoregion along the River Nile follows the border between the desert and the floodplain, and in the delta includes the former area of flood of the River Nile.
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Prepared by: Miranda Mockrin, Michelle Thieme
Reviewed by: In progress