⁠Savanna Grassland: Overview, Geographical Distribution, Ecology, Threats and Conservation Efforts

Savanna is one of the most beautiful and ecologically significant landscapes on our planet covering nearly 20% of earth’s land surface. They are earth’s second largest terrestrial biome after forests, with the world's most spectacular species including large mammals. The word ‘savanna’ came from the Taino word ‘sabana’, which means treeless grasslands. Initially, the word was in use by the Caribbean people to denote open, treeless plains. Later, this word was adopted by Spanish explorers and became the scientific name of this ecosystem.

Table of Contents

• What is ⁠Savanna Grassland
• Climate and Seasons of Savanna Grassland
• How is Savana Different from other Ecosystems
• Where are Savanna Found
• Types of Savanna
• Flora and Fauna of Savanna
• Threats to Savanna Grassland
• Conservation of Savanna Grassland
• Frequently Asked Questions about Savanna Grasslands

What is ⁠Savanna Grassland

A savanna grassland is a type of mixed woodland-grassland ecosystem that is characterised by the widely spaced trees and continuous cover of grasses. This tropical and subtropical grassland ecosystem has scattered trees and shrubs that cover 10% to 40% of the ground area and they do not form a closed canopy. With a strong seasonal water availability, savannas are also characterised by tropical wet and dry seasons.

Climate and Seasons of Savanna Grassland

The savanna climate is defined by two contrasting seasons: a wet season and a dry season. 

Wet Season: Savanna is characterised by the wet season. The duration of wet season is typically five to eight months and depending on the location this varies. During the wet season, most of the year’s rainfall arrives in intense bursts, often as afternoon thunderstorms that help grasses to grow rapidly, reaching full height. Animals roam across the landscape as food and water is abundant. 

Dry Season: Savanna grasslands are dry for around four to seven months with no or little rainfall. During the dry season grass becomes dry, trees shed their leaves and waterholes shrink or disappear. Animals during the dry season stay near to the remaining water resources and become lean due to scarcity of food.

Rainfall: Savannas receive rainfall in the wet season that ranges between 500 to 1,500 mm. The temperaturesin savanna grassland are usually warm to hot all around the year. The average temperatures often range between 20 degrees Celsius to 35 degrees Celsius, with slight variation between seasons. The hottest days are just before the rain after the dry season. 

How is Savana Different from other Ecosystems

Savannas are different from other ecosystems due to their unique characteristics: somewhere between open deserts and dense forests. Let’s learn about these differences and compare each feature such as climate, landscape, season, distribution and rainfall, etc. 

Feature	Savanna	Tropical Forest	Desert	Temperate Grassland
Tree cover	Scattered trees cover around 10 to 40% of the total area	Dense, closed canopy	Very sparse or none	Very sparse
Rainfall	500 to 1,500 mm per year	Over 2,000 mm per year	Under 250 mm per year	250 to 750 mm per year
Seasons	Wet(summer) and dry(winter)	Little seasonal variation	Dry year-round	Cold and warm seasons
Dominant plants	Grasses with scattered trees	Trees and dense understory	Succulents and shrubs	Grasses and herbs
Fire	Frequent and ecologically important	Rare	Rare	Occasional
Large mammals	Extremely abundant	Moderate	Low	Moderate
Location	Tropics and subtropics	Tropics	Global	Mid-latitudes

Where are Savanna Found 

Savannas are found in a broad belt across the tropics and subtropics on either side of the equatorial rainforest zone roughly between latitudes 5° and 20° north and south of the equator.

• Africa: East, west and south Africa has the most extensive distribution of savanna grasslands stretching around different countries including Tanzania, Uganda, Ghana and others. It constitutes around 65% of the total world’s savanna. 
• South America: Brazil has a savanna spread across 2 million square kilometers of area. They are also found in Venezuela and Colombia in South America.
• Australia: Savannas are located in the northern region of Australia including Queensland and Northern territory. 
• Asia: Tropical grasslands ecosystems are found in some parts of India including Deccan plateau, Madhya Pradesh and parts of Rajasthan. Other Asian countries such where these grasslands are found include Srilanka, Thailand and Myanmar.

Types of Savanna

Based on tree density of trees and vegetation, savannas can be categorized into following sub-types:

• Wooded savanna: With higher tree density these savannas are transitional ecosystems that are woodland-grasslands.
• Tree savanna: This a classic savanna with moderate tree cover and scattered shrubs.
• Shrub savanna: It is a savanna grassland that is dominated by shrubs rather than trees.
• Grass savanna: With very few trees this savanna is almost pure grassland.
• Flooded savanna: Found majorly along rivers, this savanna is inundated with water that supports both aquatic and terrestrial wildlife.

Flora and Fauna of Savanna

Savanna vegetation is characterized by a mix of sprawling grasslands, scattered fire-resistant trees and shrubs that adapt to its seasonal changes. Animals found in the savanna grassland primarily include grazers such as wildebeest, zebra, buffalo, impala and Thomson’s gazelle.

Browsers that eat tree leaves and shoots such as giraffes, kudu, elephants and black rhinoceros and mixed feeders that eat both grass and trees: elephant, impala. Some species have an influence on the ecosystem far out of proportion to their numbers including elephants, termites, and lions.

Threats to Savanna Grassland

Savannas are among the world's most threatened and least protected ecosystems. Human activities such as agricultural conversion, climate change and excessive livestock grazing are some of the major threats to the savanna grasslands. Poaching and illegal wildlife trade has been major challenges in saving the biodiversity of this unique ecosystem. 

Conservation of Savanna Grassland

Savannas are diverse ecosystems that cover around 40% of the earth’s surface. They are major carbon sinks that store carbon mostly underground in soils rather than in trees. Conserving savannas requires protecting them from afforestation, overgrazing and agricultural conversion. African and Australian savannas are protected by some of the world’s most famous national parks and reserves. Indian grasslands are the least studied and most threatened ecosystem. They have been undervalued in conservation policy and many conservation experts argue that India’s grassland crisis is as urgent as its forest crisis.