Forests play a crucial role as valuable repositories of biodiversity, eradicating the habitat that supports numerous plant and animal species. In Nigeria, this phenomenon has resulted in the endangerment of various trees, shrubs, and animals, with some species facing depletion.

Deforestation refers to the removal of trees without replacing them, driven by various motives such as agriculture, construction (including housing, roads, bridges, and dams), as well as for fuelwood, timber, charcoal, and medicinal purposes. Over time, forests have been intentionally cleared for various reasons, including expanding agricultural land, creating space for livestock grazing, and obtaining timber for fuel, industrial processes, and building materials. This practice has been observed throughout history and continues to be prevalent in present times. The expanding human presence in natural habitats causes intensifying resource exploitation and poses risks to biodiversity.

Deforestation is a slow hazard that gradually contributes to disaster through flooding, drought, and desertification and is among the Global Environmental Challenges affecting the whole world requiring the attention of the international organizations. Studies show that both the tropical and equatorial rain forest is shrinking at alarming rate due to deforestation activities.

Deforestation poses a major challenge in Nigeria, resulting from multiple factors such as agricultural expansion, logging, and mining. This phenomenon carries adverse consequences for both the environment and society. The removal of forests contributes to soil erosion and degradation, diminishing land fertility and hindering agricultural productivity. Moreover, deforestation plays a role in climate change as it releases carbon dioxide into the atmosphere. Another concerning outcome is the loss of biodiversity, including the potential extinction of various plant and animal species.

Deforestation is often driven by the need to create space for agricultural activities, such as farming, livestock grazing, or the establishment of plantations. Additionally, deforestation may occur to make way for infrastructure development, urban expansion, industrial projects, or other forms of human settlement. The process of deforestation involves clearing the existing forest vegetation, which includes felling trees, removing undergrowth, and eliminating other forms of plant life. This alteration of the land results in the loss of forest characteristics, including the canopy cover, biodiversity, and ecosystem services associated with the forest ecosystem.

The depletion of biodiversity in Nigeria is a growing concern, particularly in certain states within the northwestern and northeastern geopolitical regions. This alarming trend is exacerbated by the adversarial effects of desertification. The Sahel region and parts of the savannah region are particularly vulnerable to the threats of drought and desertification, leading to a range of issues such as soil erosion and the disruption of entire ecosystems. The destruction primarily affects aromatic plant species that serve as valuable medicinal resources, contributing to the economic well-being of communities in the Sahel. The human practices and their effects on these plant species have posed a significant threat to their survival. Some of the species facing endangerment 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.

Tree logging causes deforestation 
Tree logging refers to the activity of extracting trees from forests, preparing them for use, and transporting them to sawmills. This involves harvesting the trees, cutting them into suitable lengths (known as bucking), and moving them to the sawmill through a process called skidding. The specific methods and stages of logging can vary depending on local factors, such as environmental conditions and available technology.

Tree logging involves the practice of felling trees for timber production. When conducted extensively, it can have the detrimental effect of causing deforestation, which refers to the widespread destruction of trees within a forested area. This destructive process is often employed to clear large land areas for non-forest purposes, leading to the conversion of the land for other uses. Deforestation carries various negative consequences, including the release of higher levels of carbon dioxide into the atmosphere. Trees play a vital role in carbon sequestration as they absorb carbon dioxide during photosynthesis and store it within their wood. Hence, when forests are destroyed, the carbon that was once stored in trees is released back into the atmosphere, contributing to the greenhouse effect and climate change.

Furthermore, deforestation results in the loss of habitat for numerous animal and plant species that depend on forests for their survival. These ecosystems provide crucial homes, food sources, and breeding grounds for a wide range of organisms, and their destruction can lead to the decline or even extinction of various species.

Overall, the impact of tree logging and subsequent deforestation extends beyond the loss of trees. It encompasses environmental, ecological, and climate-related implications that highlight the importance of sustainable forest management and conservation efforts.

Types of tree logging

Selective logging 
As the name suggests, the selective cutting system is characterized as the least harmful approach to logging. What sets selective cutting apart is its targeted removal of trees based on specific criteria such as type, size (or age), and quality. Logging companies employing this method are usually contracted by entities seeking a particular wood species or quantity. The main advantage of selective cutting is its minimal impact on the growth of surrounding trees. However, a drawback is that it becomes progressively costlier over time due to the slower regeneration process.

Selective logging refers to the practice of selectively cutting down trees in a forest, typically targeting specific tree species or sizes for timber extraction. This type of logging can have significant impacts on tree species diversity, which refers to the variety of tree species present in a given area. One of the main ways in which selective logging affects tree species diversity is through changes in the composition of tree species. When large trees are selectively removed, it can create gaps in the forest canopy, allowing for the establishment and growth of early successional tree species that are adapted to open environments. This can lead to a shift in the overall species composition, with a decrease in the abundance of original tree species and an increase in the abundance of these early successional species.

However, the impact of selective logging on tree biodiversity is not universally agreed upon. Some studies suggest that selective logging can have negative effects on biodiversity, as the removal of large trees may result in the loss of habitat for certain tree-dependent organisms and disrupt ecological interactions within the forest ecosystem. On the other hand, other studies propose that selectively logged forests can still support a relatively high level of tree species diversity, especially if rare species have higher survival rates due to reduced competition for resources in the disturbed environment. In undisturbed tropical forests, rare species often exhibit higher survival rates because they have adapted to specific ecological niches or environmental conditions. If this non-random process of higher survival for rare species also occurs in logged forests, it can contribute to the rapid recovery of tree species diversity. Over time, as the forest regenerates and matures, a more diverse array of tree species can establish and coexist.

The exact outcomes of selective logging on tree species diversity depend on various factors, including the intensity and frequency of logging, the specific logging practices employed, the ecological characteristics of the forest, and the ability of the forest to regenerate and recover. Ongoing research and monitoring efforts are crucial to better understand the complex interactions between logging and tree species diversity, ultimately informing sustainable forest management practices and conservation strategies.

Clearcutting, a logging practice characterized by the uniform removal of most or all trees in an area, can have notable consequences on the diversity of tree species. This method of logging has the potential to result in habitat loss and a decline in species diversity. Additionally, clearcutting can create favorable conditions for the proliferation of invasive and opportunistic species, further disturbing the delicate ecological equilibrium.

Clearcutting, as a logging technique, involves the complete removal of all trees within a designated area. This practice has raised concerns due to its potential negative impacts on tree species diversity and the overall ecosystem. One of the main consequences of clearcutting is the loss of habitat for various plant and animal species. When an entire area is cleared, the natural shelter, food sources, and nesting sites provided by the trees are eliminated. This disruption can negatively affect the survival and reproduction of many species, particularly those that rely on specific tree species or forest conditions for their survival. Moreover, clearcutting can create an environment that is conducive to the spread of invasive and weedy species. With the removal of the dominant tree species, opportunistic plants that are highly adaptable and fast-growing may quickly colonize the area. These invasive species can outcompete native species, reducing overall biodiversity and altering the structure and functioning of the ecosystem. Clearcutting can lead to other ecological disturbances. The removal of trees can result in increased soil erosion, as the tree roots that help bind the soil together are no longer present. This can lead to sedimentation in nearby water bodies, impacting aquatic ecosystems and water quality. The loss of trees can also affect nutrient cycling and carbon storage, disrupting the natural balance of the ecosystem.

Overall, the practice of clearcutting raises concerns about the long-term sustainability of forests and their ability to support diverse plant and animal communities. As a result, alternative logging practices that prioritize the conservation of biodiversity, such as selective logging or sustainable forestry management, are being advocated for to mitigate the negative impacts of clearcutting on tree species diversity and ecosystem health.

Clearcutting is a method of tree removal where all trees in an area (approximately 20 acres or more) are removed. It's the most common form of tree removal due to it being the easiest and most efficient way to handle lumber. In the Canadian province of Ontario, clear-cuts can remove trees from areas as large as 10,000 hectares.

Clearcutting has been a controversial subject because of its environmental impact. While those who favor this method argue that it allows regenerating trees to have more access to sunlight while it reduces the risk of forest fires in some high-risk areas, opponents point out that in many cases, mass tree removal has caused soil erosion and the destruction of natural habitats for some animals.

Shelterwood 
Shelterwood cutting is a tree logging method that aims to achieve even-aged timber stands while avoiding the complete removal of all trees as in clear-cutting. This technique involves a series of planned cuttings, where trees are selectively harvested in a way that allows new seedlings to regenerate from the seeds of older trees.

Shelterwood cutting is a silvicultural system that involves the removal of mature trees in a series of cuts, leaving some trees standing to provide shelter for the regeneration of new seedlings. The first cut, called the preparatory cut, removes trees that are competing with the desired species for sunlight and nutrients. The second cut, called the seed cut, removes more mature trees to open up the canopy and allow more sunlight to reach the forest floor, stimulating the growth of new seedlings. The final cut, called the removal cut, removes the remaining mature trees once the new seedlings have become established. Shelterwood cutting is used to promote the growth of shade-intolerant tree species and to maintain an uneven-aged stand structure.

Plant Species Diversity
Species diversity is measured through a combination of species richness (the number of species present) and species evenness (the abundance of each species). Species richness and evenness can be combined into a single indicator, and in ecology the Shannon Index is commonly used.

Plant diversity plays a vital role in maintaining the well-being of ecosystems. In a biodiverse environment, each organism contributes significantly to the regulation of natural processes and growth cycles. This ensures that if one aspect of the ecosystem becomes excessively dominant, other components step in to restore balance. Preserving areas with higher plant diversity offers several benefits, including more stable carbon sequestration rates, protection against desertification and ecological disruptions, and providing a buffer for animal populations during extreme climate events. Additionally, plant diversity has the potential to serve as a cost-effective alternative to numerous agricultural inputs, such as fertilizers, pesticides, imported pollinators, and irrigation.
 An increased abundance of plant species leads to a wider range of crop options. Greater diversity among plant species promotes the natural sustainability of all living organisms. Robust ecosystems with high species diversity exhibit enhanced resilience and recovery capabilities when faced with various disasters or disturbances.

Tree Species in Nigeria 

The assessment of tree composition and distribution is essential for gaining insights into the condition of forest stands, regeneration patterns, and overall biodiversity, which are crucial for conservation purposes. The structure of forest areas is greatly influenced by the ecological characteristics of the sites, the diversity of tree species, and the regeneration status of these species. Obtaining quantitative data on the composition, distribution, and abundance of tree species is of utmost importance for comprehending the status, including the composition and structure, of a forest area. Such information is vital for making informed decisions, planning, and implementing effective conservation strategies for the forest estate(s). Species richness and diversity of tree species are fundamental to total forest biodiversity, because trees provide resources and habitat for almost all wildlife species.

Gmelina arborea (PROTA) 
Gmelina arborea is a tree species that is indigenous to regions spanning from Pakistan to Sri Lanka, and eastward to Myanmar, Thailand, Vietnam, and southern China. Due to its rapid growth, it is widely cultivated in tropical regions across Africa, Asia, and America. In tropical Africa, Gmelina arborea is extensively planted in numerous countries, with notable large-scale plantations present in Senegal, Gambia, Sierra Leone, Côte d'Ivoire, Mali, Burkina Faso, Ghana, Nigeria, Cameroon, and Malawi. The collective area covered by Gmelina arborea plantations in Africa is estimated to be around 130,000 hectares.

The timber derived from Gmelina arborea has diverse applications and is well-suited for various utility purposes. It is commonly used in light construction, structural work, general carpentry, packaging, carvings, utility furniture, and decorative veneers, owing to its excellent woodworking properties. Additionally, the wood finds utility in light flooring, musical instruments, matches, particle board, mine timber, vehicle bodies, and ships. Treated with preservatives, it can serve as telephone posts. Gmelina arborea also yields high-quality pulp, with semi-chemical pulp suitable for carton board or low-grade writing paper, and kraft pulp suitable for higher-grade writing paper. The wood is often utilized as firewood and charcoal as well.

References

Deforestation
Biodiversity