Account for the decline of savannah vegetation cover in East Africa. 

 

A candidate is expected to define the term savanna vegetation

 

Savanna vegetation lies between the tropical forest zone and desert areas.

 

A candidate should identify the three forms of savannah vegetation found in East Africa, their distribution and characteristics.

These are:

Tropical woodland/savannah wood land

It lies near tropical rain forests. Very common in parts of western and south western Tanzania (Miombo woodland), some parts of Northern Uganda, parts of Rift valley region like the lake George and Albert flats, parts of South and Eastern Kenya etc.

Characteristics

• Continuous cover of trees
• Trees are of moderate height (8-16m high)
• Trees are umbrella shaped
• There is dense growth of grass, bushes and shrubs (dense undergrowth).
• Trees are intermingled with xyrophytric thorny Iianas, cacti and a few hardy shrubs.

 

Savannah grassland

This lies between woodland and dry thicket bushes. Very common in the Nyika plains of Kenya, rift valley floor of western Uganda, northern Uganda and also areas around Bukoba in Tanzania            etc.

Characteristics

• The dominant vegetation are grasses that grow up to height of 1m high.
• The dominant grass species include elephant and spear grass.
• There are scattered short trees.
• The grass cover turns brown during dry seasons and green during wet seasons.

Dry bush and thicket/scrub dry savannah vegetation

Very common in Northern, Western, North-Eastern and North Western Kenya. (Turkana land), North-Eastern Uganda (Karamoja,) some parts of Ankole – Masaka corridor, parts of central Tanzania etc.

Characteristics

• Have thorny -bushy trees with scrub growing in between.
• Very short grasses more tufted with bare land between the scattered thorny bushes.
• Stunted trees with woody stem.
• Less than 8 meters in height

 

NB: General characteristics that cut across all the forms of savannah vegetation include:–

• Umbrella shaped trees
• Deciduous trees (shade off leaves during dry seasons.
• Dominant tree species include Acacia, baobabs, cacti etc.
• Trees have gnarled trunks (twisted) with thick barks.
• Trees have tinny leaves to restrict transportation.
• Trees tend to be drought resistant i.e. have thick barks, swollen trunks and long tap roots.
• Trees are fire resistant.
• Most trees develop branches close to the ground
• Trees have waxy barks and leaves

 

NB: A candidate should identify and describe the factors for the decline of savannah vegetation in E.A with illustrations.

Human activities which include:

• Over stocking which has led to over grazing, changing grassland to dry thicker
• Uncontrolled bush burning for fresh pasture has changed grassland to dry savannah.
• Tree cutting for building materials has destroyed woodland turning it into grassland.
• Clearing of woodland savannah vegetation to create land for cultivation and settlement has changed woodland into grassland. Very common in Kayunga district.
• Mining/quarrying activities have led to the destruction of wood land changing it into savannah grassland common in Busia, Mubende etc.
• Increased demand for fuel wood e.g. firewood and charcoal has led to wood land changing into grassland common in Nakasongola.
• Construction of transport routes like roads, railway lines has led to clearing of wood land savannah turning it into grassland.
• Industrialization in E.A has led to the destruction of savannah woodland due to a wide demand of land and firewood. E.g. Hima and Tororo cement factories have changed the woodland into grassland.
• Borehole drilling that lowers the water table bas transformed the grassland into dry savanna.

Other factors:

• Prolonged dry seasons that have led to desert conditions e.g. in Eastern Uganda, Eastern Kenya changing the grassland into dry bush and thicket
• Pests and diseases e.g. termites, caterpillars, harvester ants have destroyed savannah grassland vegetation changing into dry bush and thickets. Common in Nakasongola, Katakwi district etc.
• Natural fires during prolonged dry seasons have destroyed savannah grassland changing it into dry thickets. E.g. in Northern Kenya.
• Use of savannah grasslands as game parks has led to over grazing of grass and browsing of trees by wild animals e.g. elephants turning it into dry bush and thickets e.g. Murchison fall national park.
• Influence of the dry prevailing winds which further intensify the drying effect has led to the degeneration of grasslands to dry bush and thickets. E.g. North Eastern Kenya etc.