The African savanna ecosystem is a tropical grassland with mild temperatures throughout the year and the most rainfall during the summer. A varied population of organisms coexist in the African savanna to construct a complex food chain.
A savanna grassland, sometimes also known as savannah, is a part of a more expansive grassland biome with sufficiently spread trees, so the canopy does not collapse. The open canopy allows enough light to reach the ground to allow grass growth.
Savanna grasslands typically thrive in hot and humid climates or tropical climates. The temperature in savannas tends to vary between warm and hot. However, rainfall may occur in the Southern and Northern Hemispheres from October to March and April to September. The average rainfall is usually in between 80 to 150 inches, but sometimes, it can go below 50 inches in a few continental areas. The dry season is generally longer by a couple of months than the wet season, and can last anywhere between two to 11 months. The temperatures generally range from 50 – 68 °F in the dry season and can go up to 68 – 86° F in the wet season.
Depending on the length of the dry season, there are three types of savanna:
The dry season lasts three to five months in wet savannas, five to seven months in dry savannas, and even longer in thornbush savannas. Another classification distinguishes savanna woodland, which has a light canopy of trees and shrubs; tree savanna, which has dispersed trees and plants; shrub savanna, which has scattered shrubs; as well as grass savanna, which has no trees or plants. Other ways of classifying savannas have been proposed as well.
All types of savannas, irrespective of their diversity or differences, have a few elements that are similar. They are either tropical or subtropical vegetation with a large cover of grass, trees, and shrubs. These trees and shrubs are prone to wildfires and grow as per the alternating wet and dry seasons. They can be considered as a middle zone between tropical rainforests and the hot deserts.
Threats to the Savanna
Changes in firefighting tactics
Wildfires are common in savanna grasslands, and the ecological threat seems to be the result of irresponsible human fire use. These fires are usually limited to the herbaceous layer, and established trees suffer little long-term harm. On the other hand, these fires either kill or inhibit tree seedlings, preventing the formation of a continuous forest canopy that would promote additional grass growth.
Grazing of animals
Because the closed structure prevents grass development, forest types such as broadleaf forests and rainforests are rarely grazed. On the other hand, Savannas have an open structure that allows a herbaceous layer to grow and are widely used for grazing domestic livestock. As a result of grazing by sheep, goats, and cattle, most of the world’s savannas have changed, resulting in major ecological shifts, from changes in pasture composition to encroachment by woody weeds.
The grazing sector clears land to improve livestock management and increase the quality and quantity of feed available. The removal of trees from the savanna area reduces competition for water among the grasses, resulting in a two- to fourfold increase in pasture output and improved feed quality. Because stock carrying capacity is inversely proportional to herbage yield, removing trees can have significant financial benefits, such as assisting with grazing management: dense tree and shrub cover attracts predators, resulting in increased stock losses; for example, woody plant cover impedes mustering in both sheep and cattle areas.
The Savanna biome mostly comprises smooth, uneven grassland plants and is part of a bigger grassland biome. The Savanna biome, which is also popularly called the tropical grassland and temperate grassland, originates from this grassland biome.
Despite their variance, the two biomes share one prevalent feature: grass, which is paramount for the ecosystem’s survival, and is the primary reason behind the name ‘grassland.’ The Savanna biome is characterised by grasses as the prominent ground cover, with a few trees and shrubs dispersed and spread around the area.