**Abstract**

The loss of biodiversity in Nigeria is intensifying distressingly, which happened to be more prominent in some states across northwestern as well as north eastern geopolitical regions of Nigeria and was threatened by the confrontational effect of desertification. The Sahel region and some part of the savannah region bordered which faced the menace of drought and desertification which lead to so many factors like soil erosion, distraction of the ecosystem entirely. Moreover, the plants destroyed were mostly aromatic plants which served as medicines in curing many ailments and diseases contributed to the economic status of the communities found in the Sahel. The plants species became threatened to the human practices by noticing their effects for their well-being. Consequently, among the species that were threatened include: *Neocarea macrophylla* Prance ex F.White (Gawasa), *Sclerocarya birrea* (A. Rich) Hochst. (Danya), *Detarium microcarpum* Harms. (Taura), *Prosopis africana*, (Kirya), *Acacia africana*, *Acacia nilotica* and *Azadirachta indica*. Hence, the major concern of this chapter is to assess some of the threatened species found in the Sahel region, Nigeria and to highlight the valuable medicinal plants at risk of extinction according to the guidelines of the International Union for the Conservation of Nature (IUCN).

**Keywords:** African, dessert plants, medicinal plants, threatened, ethnobotany

## **1. Introduction**

The loss of biodiversity in Nigeria is intensifying distressingly ("Assessment of the threats to biodiversity" Convention on Biological Diversity [CBD]), which happened to be more prominent in some states across northwestern as well as north eastern geopolitical regions of Nigeria and was threatened by the confrontational effect of desertification, posing a substantial threat to the well-being of the populace [1]. The Sahel region and some part of the savannah region bordered with Niger Republic faced the menace of drought and desertification that leads to soil erosion and distraction of the ecosystem entirely (**Figure 1**). The confrontational effect is caused by the rampant cutting of trees, loss of ground cover and continuous overgrazing by livestock of the Fulani herdsmen. Moreover, the plants destroyed were mostly aromatic and medicinal plants gathered, traded and used by communities in Sahel as source of livelihood. Consequently, among the species that were threatened include *Neocarea macrophylla* (Sabine) Prance ex F.White

**Figure 1.** *Map of Yobe State, Nigeria (Sahel region).*

(Gawasa), *Sclerocarya birrea* (A. Rich) Hochst. (Danya), *Detarium microcarpum* Harms. (Taura), *Prosopis africana* (Guill. and Perr.) Taub. (Kirya), *Acacia africana*, *Acacia nilotica*, *Azadirachta indica* [2]. Though numerous international and national summit have been conducted towards ways to tackle the menace of desertification but apparently failed in the Sahel regions, notably because majority of the populace relied on the natural resources for their well-being. The genus *Acacia* with about 1380 species is widely distributed from Australia to rest in tropical and subtropical regions of the globe is called "*bagaruwa"* by the Hausa tribe (Sudan and Nigeria). It is used to treat many ailments by utilizing its leaves, stem and pods simply because the abused of many commercially made antibiotics has led to many antibiotic resistances in human pathogens [2]. Consequently, *S. birrea* considered to be native African tree and widely distributed across the continent. Its stem-bark, roots, leaves and fruits are contained a myriad of chemical components, which attributed to its utilization as food and traditional medicine for many ailments. Its fruits were

*Noteworthy Threatened Plant Species in the Sahel Region, Nigeria DOI: http://dx.doi.org/10.5772/intechopen.93975*

regarded as wild fruits for their uniqueness of nutritional attributes of ascorbic acid and other hydrocarbons. The seeds possessed essential acids and oil used as antiinflammatory, antidiabetic, analgesic, anti-parasitic, antimicrobial and antihypertensive [3]. Hence, *S. birrea* (marula) is commercially valuable as many tribes in Africa used its stem-bark for making inks. The wood part of "marula" mainly used for dishes, mortars, drums, toys, curios and cosmetics oil [4]. It has become a challenge to Nigerian Ministry of Health over many years because both rural and urban communities opted to medicinal plants as complementary and alternative medium of curing their ailments, and over cutting unsustainably and lack of enforcement caused some species into verge of extinction [5].

#### **1.1 Loss of biodiversity**

Evidences showed that the biodiversity has been unprecedentedly lost at a higher rate in many parts of Nigeria, which are mostly human related factors such as industrialization, technological advancements and settlements for urbanization. Biodiversity loss in Nigeria is mainly due to poor law enforcement, high demand for forest products and cultural practices. In addition, clearing of vegetation haphazardly leads to loss in biodiversity. However, biodiversity loss may also due to some agricultural and livelihood practices such as firewood cutting and gathering, bush burning, logging and overgrazing. Since 1990s, some large farm has caused enormous deforestation of the natural habitats depicting as the major source of loss. Thus, drastic depletion of fire-wood species like neem tree, *Acacia nilotica*, *Acacia seyal* was very prominent [6]. Consequently, the Sahel region is characterized by small, widely disseminated, small-leaved trees, mainly *Acacia* species such as *Acacia tortilis subsp. raddiana*, *Acacia seyal*, *Acacia nilotica* and *Acacia senegal*. Equally high percentage of the trees was deciduous in the dry season. Some species were *Anogeissus leiocarpus*, *Sclerocarya birrea* (**Figure 2a**), *Combretum micranthum* and *Guiera senegalensis*. Interpretation of radar imagery distinguishes the following (predominantly) shrub vegetation types: "Dense shrub grassland" and "shrub grassland" which offer a woody cover of shrub like *Combretum* spp., *Guiera senegalensis*, *Acacia* species, *Calotropis senegalensis* and *Boscia senegalensis*, adequately classified them as wooded formations [6].

#### **1.2 Plants species utilization patterns**

Northern Sahel region of Nigeria nutritional habits are equivalent with slight variations influenced by traditional backgrounds. All the trees selectively protected in the parklands provide one or combinations of the following concrete and immaterial services: food items (edible fruits, nuts, leaves, flowers, livestock fodder, fuel wood, medicine, esthetics, shade, agricultural tools and cooking utensils, avenues, and other services such as ropes, fibers, tannin, manure, latex gums and oils). Patterns of exploitation are quite similar for the entire region. However, additional trees were protected based on their medicinal values and food, Fire wood (fuel energy and heating) stand equally of importance, with the exception of *Adansonia digitata* and *Calotropis procera*, all species were utilized as fire wood obtained from prunings, complete felling or pollarding [6]. All the constituent parts of the tree featured regular and often in the food security and nutritional resources for the people and with some quantity sole in the market as sources of income. Many of the cattle farmers still rely substantially on those trees for chopped forage, while the fruits, shells were also fed to the livestock. Shade provision was unique with *Parkia biglobosa, Adansonia digitata* and *Tamarindus indica* alongside with *Mangifera indica* due to their broad canopies. Currently, income from the sales

#### **Figure 2.**

*Threatened useful plants from the Sahel region in Nigeria. (a)* Sclerocarya birrea*, (b)* Acacia seyal*, (c)* Azadirachta indica*, (d)* Acacia nilotica*, (e)* Balanites aegyptiaca*, (f)* Detarium microcarpum*, and (g)* Tamarindus indica.

of fruits of *Parkia biglobosa*, *Vitellaria paradoxa, Adansonia digitata, Tamarindus indica*, *Balanites aegyptiaca* and *Acacia seyal* (**Figure 2b**) accounted for 30-45% of the farmers' income. Common known exotics like *Mangifera indica*, *Anacardium* 

*occidentale* and *Azadirachta indica* (**Figure 2c**) were on a balance with most the indigenous trees and were equally threatened. Soil fertility nourishment happened to be secondary role from some of these trees through litter falls. The Sahel savannah covers an area of 31,468 km2 , where some of the species were also threatened in parks and fetish channels arising from remarkable reasons, which bans the cutting down of some species such as *Adansonia digitata*, *Tamarindus indica*, *Acacia senegal* and *Faidherbia albida* [6].

Nevertheless, small number of both species was assessed due to the fact that, many were threatened, deteriorated as a result of human and edaphic factors. Many were not assessed in the IUCN Red list due to the aforementioned factors that pressurized on them to be disappeared or not even listed in the whole list [7]. All stakeholders showed consistent preference for the following species: *Adansonia digitata*, *Acacia seyal*, *Acacia nilotica* (**Figure 2d**), *Acacia senegal*, *Anogeissus leiocarpus*, *Azadirachta indica*, *Anacardium occidentale*, *Balanites aegyptiaca*, *Borassus aethiopum*, *Ceiba pentandra*, *Combretum microcarpum*, *Eucalyptus camaldulensis*, *Diospyros mespiliformis*, *Faidherbia albida*, *Guiera senegalensis*, *Gmelina arborea*, *Hyphaene thebaica*, *Lawsonia inermis*, *Lannea acida, Khaya senegalensis*, *Moringa oleifera*, *Mangifera indica*, *Parkia biglobosa*, *Piliostigma thonningii, Pterocarpus erinaceus*, *Pinus* spp., *Salvadora perica*, *Senna siamea*, *Tamarindus indica*, *Vitellaria paradoxa*, *Vitex doniana* [8]. Highly valued naturalized exotic fruits trees including *Mangifera indica*, *Psidium guajava*, *Anacardium occidentale*, *Azadirachta indica* and *Citrus* spp. Nevertheless, *Acacia senegal* has been exploited commercially for gum Arabic with plantations existing in Yobe state, other plantations were mainly for afforestation and shelterbelts planted up with exotics including *Pinus* spp., *Eucalyptus* spp., *Gmelina arborea*, *Azadirachta indica* and *Senna siamea* [9, 10].

#### **1.3 Other threatened species**

A considerable numbers of indigenous species were reported to have declined in some years back. The focus groups credited the decline of these species due to some activities (land degradation) occurred [11]. Certain percentages have shown that the species faced a lot of problems (Ranging 36%-60%) of all the species found in the Sahel. The common plants species involved across the towns and villages were *Acacia tortilis, Ficus glumosa*, *Balanite aegyptiaca* and *Sclerocarya birrea,* whereas, some disappeared including *Albizia chevalieri*, *Acacia senegal, Ficus thonningii* and *Khaya senegalensis,* many factors have contributed towards the disappearance of those species. Furthermore, some exotic species were present and also served many roles in the environment without the much existence of those threatened species especially *A. indica* which has been proclaimed to cause a setback on the farm produce due to some negative impacts on the farm lands. The level of poverty has tremendously attributed towards the negative actions across the threatened plants species, for the search of food, shelter and other agricultural practices and very poor planting and management of trees across the region [12].
