Editing Sudd (section)

==Vegetation and ecosystem==
Vegetation cover of the area can generally be classified in five categories which depend on the elevation of the area above river flood level: the lakes and rivers, the floating plant life of the swamp, river-flooded grasslands (Toic), rain-flooded grasslands, and wooded grasslands on the fringes. Grassland and woodland areas have been cultivated by local populations.

The density of the grasslands along the Sudd changes with the season, with tall grass in the rainy season and short dry grass in the dry season, when frequent fires also occur. The fluvial area is mostly overgrown with vegetation, with some main and side channels as well as lagoons of open water. The vegetation distribution is described in further detail in Sutcliffe (1974) and Petersen (2007). The main species are:

* ''[[Phragmites communis]]'' (shallow flooded, buried roots)
* ''[[Echinochloa pyramidalis]]'' (shallow flooded, buried roots)
* ''[[Oryza barthii]]'' (shallow flooded, buried roots)
* ''[[Echinochloa stagnina]]'' (deep flooded, superficial/floating roots)
* ''[[Vossia cuspidata]]'' (deep flooded, superficial/floating roots)
* ''[[Cyperus papyrus]]'' (deep flooded, superficial/floating roots)
* ''[[Typha domingensis]]''

The first three species are anchored so their distribution is limited to the depth of flooding. For the last species their root system needs to be permanently in water or saturated soil, which is a good indicator of flood patterns. ''P. communis'', ''E. pyramidalis'' and ''O. barthii'' for example dominate only in areas where the depth of flooding does not exceed 130&nbsp;cm over a period of ten years or 118&nbsp;cm for one month in the year.

Floating vegetation of ''C. papyrus'' had caused blockages in the Sudd swamps on a number of occasions between 1879 and 1900, when the plants were torn out by increased flooding. ''C. papyrus'' needs saturated conditions and can tolerate flooding that is not more than 150&nbsp;cm deep.<ref>{{cite journal |last=Sutcliffe |first=J.V. |title=A Hydrological Study of the Southern Sudd Region of the Upper Nile |journal=Hydrological Science Bulletin |volume=19 |issue=2 |year=1974 |pages=237–255 |doi=10.1080/02626667409493903}}</ref>

When the matted vegetation breaks free of its moorings, it forms floating islands of vegetation up to 30&nbsp;km in length. Such islands, in varying stages of decomposition, eventually break up.

Historically, the fully floating [[Pistia|Nile cabbage]] (''Pistia stratiotes'') was an important plant in the Sudd, but it has largely been replaced by the invasive [[Pontederia crassipes|water hyacinth]] (''Eichhornia crassipes'').<ref name=Green2009>{{cite book |author1=Green, J. |author2=A.I. El-Moghraby |chapter=Swamps of the Upper White Nile |pages=193–204 |editor=H.J. Dumont |title=The Nile |series=Monographiae Biologicae |publisher=Springer Science + Business Media B.V. |volume=89 |year=2009 |isbn=978-1-4020-9725-6}}</ref> The sluggish waters are host to a large population of [[mosquito]]es and [[parasite]]s that cause [[waterborne diseases]].

===Fauna===
Including several diverse aquatic habitats like swamps, lakes, channels and floodplains, the Sudd is rich in fish. Some 70 species have been recorded, and this mostly involves fish that are found in much of the Nile system such as [[marbled lungfish]], [[Polypterus senegalus|Senegal bichir]], [[African arowana]], ''[[Mormyrus caschive]]'', [[Nile carp]], [[Nile tilapia]], [[mango tilapia]], [[redbelly tilapia]], [[Nile perch]], ''[[Distichodus]] rostratus'', [[Hydrocynus forskahlii|elongate tigerfish]], [[Alestidae|African tetras]], [[Clarias gariepinus|African sharptooth catfish]], ''[[Synodontis frontosus]]'', ''[[Synodontis schall|S. schall]]'' and others.<ref name=Green2009/> Among the few [[Endemism|endemics]] of the Sudd system are ''[[Clarias]] engelseni'', ''[[Enteromius yeiensis]]'', ''[[Nothobranchius]] nubaensis'', ''N. virgatus'' and two apparently [[Undescribed taxon|undescribed species]] of ''[[Enteromius]]'', and the fish fauna in significant sections still has not been properly studied.<ref name=Neumann2016>{{cite journal |author1=Neumann, D. | author2=H. Obermaier |author3=T. Moritz |year=2016 |title=Annotated checklist for fishes of the Main Nile Basin in the Sudan and Egypt based on recent specimen records (2006–2015) |journal=Cybium |volume=40 |issue=4 |pages=287–317 |doi=10.26028/cybium/2016-404-004}}</ref>

Over 400 species of bird are found in the Sudd, including [[shoebill]]s (a stronghold for the species with several thousand individuals), [[great white pelican]]s, and [[black crowned crane]]s. The Sudd provides food and water to large populations of [[Bird migration|migrating birds]]. As the surrounding landscape is a large swath of dry [[Sahel]] across Africa, the swamp is also a haven for [[Animal migration|migrating]] mammals, especially [[antelope]]s, such as the [[bohor reedbuck]], [[sitatunga]] (the most aquatic antelope of the Sudd, mostly inhabiting permanent swampland), the endangered [[Nile lechwe]] (not in permanent swampland, but generally near the water's edge and often walking in shallow water), and the [[Kob|white-eared kob]] (further away from the permanent swampland).<ref name=Green2009/> White-eared kob, [[Tiang (antelope)|tiang]] and [[Mongalla gazelle]] take part in one of the largest mammal migrations on Earth, numbering about 1.2 million individuals in total.<ref>{{cite web |title=Massive Animal Herds Flourishing Despite Sudan War, Survey Reveals |publisher=[[National Geographic (magazine)|National Geographic]] |url=http://news.nationalgeographic.com/news/2007/06/070611-sudan-animals.html |archive-url=https://web.archive.org/web/20070614213924/http://news.nationalgeographic.com/news/2007/06/070611-sudan-animals.html |url-status=dead |archive-date =14 June 2007}} January 2007</ref><ref name=Furniss2010>Furniss, C. (2010) {{cite news |url=http://findarticles.com/p/articles/mi_hb3120/is_4_82/ai_n54800827/?tag=content;col1 |title=Draining Africa's Eden. |work=Geographical |year=2010}} Geographical, April 2010.</ref> The shallow water is frequented by [[Nile crocodile]]s and [[hippopotamus]]es. In more upland areas the Sudd was known as an historic habitat for the endangered [[African wild dog|painted hunting dog]], which however may have been exterminated in the region.<ref>C. Michael Hogan. 2009. [http://globaltwitcher.auderis.se/artspec_information.asp?thingid=35993 ''Painted Hunting Dog: Lycaon pictus'', GlobalTwitcher.com, ed. N. Stromberg] {{webarchive |url=https://web.archive.org/web/20101209234758/http://globaltwitcher.auderis.se/artspec_information.asp?thingid=35993 |date=9 December 2010}}</ref>