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■Serengeti grasslands lie just south of feTanzanian/Kenyan border, between land 4° South (Figure 11.48). Mean laximum temperatures are 24* to 27°C, fdmean minimum temperatures 15° 21 "C Mean annual rainfall varies from |050mm in the north-west to 550 mm
the south-east Rainfall peaks in March p May, and November to December prnpare Figure 12.49). I The soils are formed from volcanic ph.The eco-region consists of slightly undulating grassy plains, interrupted by Scattered rocky areas (kopjes) which are parts of the Precambrian basement rocks Hotruding through the ash layers.
wBbdiversity features
phe Serengeti grasslands are vital to the |cyclical movement of millions of large I Mammals. Populations fluctuate, but about | '-3 million blue wildebeest, 200 000 plains
'.and400000Thomson's gazelle I Migrate between Serengeti and southern
Kenya each year. Many associated predators are also involved in these movements. By the onset of the dry season (late May), the grasses on the plains have either dried out or been eaten down to stubble, and water is scarce. This triggers the massive migration from the plains northwards. Then, at the start of the wet season, the animals complete the cycle, and return to the plains.
Fires, usually set by humans, are an important disturbance in this eco-region. The burning helps provide accessible pasture for the herds of cattle that are kept here but other species, including wildebeest, also favour grazing on the green flush that emerges after burning.
Currentstatus
Much of the eco-region occurs within protected areas, most of which are joined into a continuous block.The protected area includes Serengeti National Park (SNP) and Ngorongoro Conservation Area (NCA), both of which are World Heritage Sites (page 596). This area is probably large enough to ensure the survival of the habitat and its biodiversity.There has been little loss of habitat within the protected areas, except for small areas used for tourist hotels. Outside the protected areas, however, there has been a rapid expansion of human settlement and agriculture in recent years.
Types and severity of threats
While Maasai pastoralists occupy the NCA, there are no people living within the SNP. However, the western frontier of this park has a dense population, growing at 4 per cent a year. Livestock numbers are increasing, and much of the area is being converted into cropland. Agriculture is the main source of income, but many people have been attiacted to the area by the wildlife resources and tourism opportunities that the park presents
Many animals within the SNP are killed by poachers, who may be local people hunting 'bush meat'for subsistence, organised commercial hunters taking meat for sale in the cities, or Big Game hunters taking part in organised illegal safaris.
However, it is hoped that schemes to give local communities legal rights to manage the wildlife around their villages will reduce the worst excesses of the hunting. There are also plans to channel more money earned from tourist activities within the park back into the community as, so far, the contribution from tourism to the local economy has been relatively low.
Are the Serengeti grasslands natural?
The Serengeti changed from a grassland state to woodland twice in the last century. The few old, large trees dotting the landscape started life about 1900, followed by a slow decline in numbers due to elephants, fire, disease, and natural thinning, leaving the few that we see today. The second group of smaller trees established themselves between 1976 and 1983, and these trees are still growing in abundance. Both groups were able to grow because for two periods there were neither elephants nor fires.
Rinderpest, a cattle disease, came to East Africa in about 1896. Most of the Seiengeti wildebeest died in a few years, as did the cattle herds.There was famine,followed by
Biogeography 311
Management of the Serengeti
In recent years human population has increased, putting pressure on park resources. Conflicts arise as wild animals damage property and even threaten life. Illegal poaching activities create conflict. In some sections cultivation is right on the park border and this fuels conflict as animals destroy the crops on one side or are illegally hunted on the other.
The Serengeti is a prime example of how many natural ecosystems are being eroded by human population effects, irrespective of legal boundaries. The original Serengeti-Ngorongoro 'undisturbed' ecosystem (which included indigenous hunters with traditional weapons), set aside in the 1950s, has declined steadily. Some 40% of the natural ecosystem has been lost to farming and herding. Today, there are signs that this loss may be accelerating.
The Serengeti is also losing species. Thus, rhinoceros, once abundant, have been effectively exterminated front the ecosystem, and elephants were reduced by 80%, both by poaching. Wild dogs went extinct in the early 90s, due to contact with domestic dogs and infection with diseases (ike distemper and rabies. Unregulated hunting of large predators in areas around Serengeti has had dramatic impacts. Over-hunting of male lions alters the local adult sex ratio, draws males out from the park, and thus disrupts populations within in it.
The 1989 worldwide ivory ban almost completely stopped the poaching of elephants and their numbers are recovering. However, meat poaching continues. In an average year, local people living around the park illegally kill about 40,000 animals, mainly wildebeest and zebra.
figure 11.49
Infotmationfrom the Serengeti website
but also giraffe, buffalo and iinpala. The populations of these animals seem to be able to survive this poaching without any long-term decline but the killing is a manifestation of growing antagonism between the impoverished villagers and the authorities of the SNP. This conflict did not exist two decades ago; there was land enough for everyone and every animal. What we must all face - poachers, tourists, farmers, conservationists and pastoralists - is the fact that the land does not go on forever.
In an effort to harmonize the pastoralists with the wildlife in the Serengeti, locally administered reserves - Wildlife Management Areas-are now created on the borders of the park, where villagers are given a far greater degree of control over the land and its resources. In situations where protection of biodiversity is not seen to be of clear economic benefit to the community, outside assistance must attempt to bring change by:
• increasing communily pride in their natural environment
• increasing the economic benefits of conservation, e.g. by fostering ecotourism, hiring community members as resource stewards, rangers, etc.
• rehabilitating depleted resource systems
• increasing the community's ability to control the use of the resource by outside interests.
figure 11.50
Scenes in the Serengeti
emigration. With no people there was no one to light fires and the Serengeti went un-burnt. At the same time, the trade in ivory was at its peak. With no fires and no elephants, young trees were able to grow 3nd flourish in the first big establishment of the century.Then, gradually, the wildebeest and cattle recovered and by the 1930s elephants started to return, and growth of new trees ceased.
Between 1976 and 1984 the weather patterns in and around Serengeti cnanged.The seasonal rains became more spread out, so
the grasslands did not dry and burn during thetíry season'. During this time there was an enormous upswing in the illegal ivory trade. With fire and elephants removed, the trees again established themselves in a burst. These trees are now about 30years old and range from 2 to 5 m tall, often forming dense thickets.
There has been a large increase of impala inside the park.They seem to be much more successful in the woodlands than in the grasslands, and have increased as the woodlands have increased. In the past, elephants and fire have controlled the establishment of new trees. Today, both elephants and fire are monitored closely. The Park Ecology Department burns fire-breaks to stop the spread of large fires, and conducts tool'earV bums in fire-prone areas. It is also monitoring the ecosystem carefully to see how all aspects interact.
The Serengeti National Park Authorities have two main aims:
1 to conserve the natural environment of the SNP
2 to support the traditional way of life of the people who live around the SNP.
Draw up a list of management objectives for the Park, justifying each of your objectives and explaining how individual objectives combine to form a coherent management plan for the area.
The management of grasslands
owth of this biome only ount of litter and, as ttlwJ the cold soil, organic matt^ ry slowly to give a thin pe5 or. There are many sites 1 rainage. Where this occurs 1 olate downwards, usuallya's1 ing, giving limited leachin~|
acid within it (the pH ■ lowing the release ofiron, at a very variable depth but I
is the permafrost. Thi5 I eable layer, severely restricts! and causes extreme water- •
igure 12.45). Few mixing " the cold, wet, tundra soils ave no developed horizons rctic brown soil which ained sites). Where bedrock 1 the parent material is byfreeze-thaw action. The gments are raised to the
preventing the formation inga range of periglacial
I Figure 12.46
I Tropical savanna grassland on [ I theLoita Plain, Kenya
A Tropical grasslands in Kenya
The main expanses of tropical grassland in Kenya lie within the Rift Valley and on the adjacent plains of the Mara (an extension of the Serengeti) and Loita (Figure 12.48). Their appearance is one of open savanna (Figures 12,13 and 12.46) with small acacia and evergreen trees (Figure 12.15). There h evidence, however, that the original climax vegetation was forest, but that this has been altered by fires, started both naturally and by humans (page 293), by overgrazing (Figure 12.47) and by climatic change,
The climate is very warm and dry foi most of the year with, usually, a short season (three months) of fairly reliable and abundant rainfall and an even shorter period known as the little rains (Figure 12.49). Both periods of rainfall follow soon after the ITCZ and the associated overhead sun have passed over the
Scattered trees and over-grazed land in the central RiftValley. Kenya
World climate, soils and vegetation 335
tropical grassland
highland
National Parks and reserves
The majorareas of tropical ~l grassland in Kenya
Tsavo
National Park I
Nairobi (Ken/a)
rs
altitude 1820 m
annual temperature range 3°C
annual precipitation 958 mm
30
rainfall reliab/e: soil moisture recharge and some water surplus
20
10
l300
250
200
A   S O  N D
soil soil.... _
moisture moisture
utilisation deficit
100
50
Equator (Figure 12.12).The annual water balance shows a deficit (Figure 3.3) so that, although there is some leaching during the rainy season, for most of the year capillary action occurs.This has resulted in the development of ferruginous soils with, in places, 3 lateritic crust (page 321). Water supply is therefore a major management problem in this part of Kenya.
Water is obtained from springs at the foot of Mount Kilimanjaro - the mountain itself is in Tanzania - which are fed by melting snow; from several of the Rift Valley lakes (not all, as some are highly saline); from rivers (many of which are seasonal); and from waterholes. Even so, there have been, in the last 100 years alone, several major droughts when the carrying capacity of the region was exceeded. The carrying capacity (page 378) is the maximum number of a population (people, animals, plants, etc.) that can be supported by the resources of the environment in which they live, e.g. the greatest number of cattle that can be fed adequately on the available amount of grassland.
Figure U.49
Climate graph and water balance for Nairobi (note that, due to its higher altitude, Nairobi is cooler and wetter than the surrounding grasslands)
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Human pressure on the natural resources
Maasai pastoralists
Maasai are defined as'people who speakthe Maa ianguage!Their ancestors were Nilotic, coming from southern Sudan during the first millennium AD.They kept cattle and grew sorghum and millet.The present Maasai may be descendants of the last of several migration waves. Latest evidence suggests that they may have only been in Kenya for 300 years. Over time, they speciaiised more in cattle and came to see themselves, and to be seen by others, historically and ethnically, as'people of cattle'. Figure 12,50 is a stereotype photo of the Maasai, dressed in their red cloaks and with their humped zebu cattle. While all Maasai are Maa speakers, not all Maa speakers are Maasai - nor, today, are all Maasai pastoralists!The Maasai became semi-nomadic, moving seasonally with their cattle in search of water and pasture (two wet seasons and two dry seasons meant four moves a year; Figure 12.49). Herds had to be large enough to provide sufficient milk and meat for their owners and to reproduce themselves overtime, including the ability to recover from drought and disease.
336    World climate, soils and vegetation