Flora. – The flora of Sudan constitutes the phytogeographic province of the Sudanese savannas. The physiognomy of the vegetation and flora of this vast territory is remarkably varied.
The savannas occupy vast expanses, where, in relation to the periodicity of the climate and the long periods of drought that reign there, grasses abound and particularly the Andropogonee and Panicee with a great variety of forms which, in part, are similar to the types steppici with stiff leaves. There are tall forms, such as Saccharum spontaneum (from 2 to 4 m.), But there are also species whose stature varies from 4 to 9 decimeters. Notable extensions are also occupied by steppes and semi-deserts.
Along the rivers and lakes grow vast belts of reeds and rushes in the midst of which are found floating leaves of water lilies and Pistia ; along the White Nile papyri abound together with the ambak or cork shrub (Herminiera elaphroxylon of the Leguminose family) with a spongy trunk, which develops from 3 to 5 m. on the highest level of the water, and then die down to the root in periods of lean and drought.
The arboreal vegetation is far from having the luxuriant development of the forests of other tropical areas and precious woods are rare or lacking completely: the trees hardly reach the stature of those of the European forests: in the plains and in the highlands where they are subject only to atmospheric precipitations remain low and stunted. Thus most acacias are dwarf or fruticiform. Some, however, reach considerable size in some of their organs such as: the baobab in the trunk. The woody ones are mostly deciduous.
The flowering of many woody plants occurs during the drought period, when the leaves are still enclosed in the buds that open at the rainy time: there is no lack of evergreen forms not only in the tropical areas of the territory, but also in the arid ones of Nubia where the two shrubs Balanites and Boscia keep their leaves when all around the vegetation is dry or leafless.
Among the woody plants characteristic of the Sudanese region, in the forests and savannahs, the forms of Mimosee abound, represented by the gumiferous acacias spread from Nubia to Senegambia: in the midst of them grows here and there the Tamarindus indica which, on average, reaches the size of an oak and there are other legumes and a small number of other dicotyledons. There are also scattered baobabs, whose trunks at ground level reach from 6 to 8 m. in diameter, and beautiful specimens of Ficus sycomorus, this species with rich foliage, however, remains for a long time without leaves. In the northern countries of the interior of Sudan the Capparis decidua is abundant and characteristic, bushy shrub with dense branches, thorny due to persistent stipules, which becomes arborescent on the Niger near Timbuktu. Among the palms, which are not very abundant in the Sudanese territory, are the dum palm (Hyphaene thebaica), the deleb (Borassus flabelliformis var. Aethiopum), which can reach from 15 to 30 m. high.
Succulent plants are represented by cactiform euphorbia, which form bushes of 9-12 m. tall, from Alöe species and related forms. Two Asclepiadaceae abound in the region: Calotropis procera which is found throughout northern and central Africa and goes as far east as Persia and India, but which probably has its center of origin in Sudan, and Leptadmia pyrotechnica of spartiform and evergreen appearance. Another almost aphylla plant with bluish green branches is Tamarix nilotica.
In connection with the dryness of the climate in many parts of the Sudanese territory there is no lack of fruit trees and thorny shrubs.
In relation to the special climatic conditions of some territories, bulbous plants with a rapid development cycle and capable of resisting long periods of drought are developed.
The two main formations of Sudanese vegetation are: the khala or savannah and the ghabra or forest, however the colonization of some regions has brought about profound modifications.
In the savannas it is the stature of the grasses that influences the vegetation: if they are gigantic, they form a dense mantle which excludes any other plant, apart from some trees previously mentioned; if they are instead of modest size, we find mixed Verbenaceae, Acantaceae, Asteraceae, Gigliacee, Orchidaceae, etc., with succulent forms or with cottony or woody-thorny leaves for xerophilous adaptations.
Fauna. – The fauna of Sudan includes elements of the Ethiopian fauna proper and elements of the eremian region. For the Mammals we will mention, among the Monkeys, various vervets, hamadryads, etc. Prosimians are represented by species of Lemurids. Chiroptera include numerous forms of Rhinolophids, Nicteridae, Rossette, Vespertilionidae. Among the Insectivores we will mention various Soricidae, hedgehogs and representatives of the Macroscelidae family. Carnivores are well represented with many species of viverre, ichneumon, hyenas, foxes, jackals, the lion and various other felines. Gnaws include many forms of Spalacidae, porcupines, octodonts, squirrels, mice, hares, etc. Among the ungulates we will mention the presence of the elephant, the rock bird among the iracoids, numerous antelopes, the giraffe, the hippopotamus, the zebras, and the two-horned rhinoceros. Orycteropus and various pangolins. The avifauna are very rich and there are also numerous reptiles as well as amphibians and freshwater fish. The fauna of the invertebrates includes very numerous species, particularly as regards the group of insects and its relatives.