Demography of Human Populations in Arid Areas

H. Lang, M. Bollig

In studies on disasters, demographic growth is frequently not discussed, although in general population growth is thought of as a major reason for the increased vulnerability of rural communities in Africa. Africa’s population growth rate (about 3 per cent per annum) has been tremendous over the last few decades and far ahead of other continents. The Sahelian countries showed a growth rate of 2.4 per cent, while countries in the southern African dry-belt had a growth rate of 3 per cent. Kenya has topped the list for long with a staggering growth rate of 3.8 per cent per annum - one of the highest scores in a global comparison. The rapid growth of the human population was not matched by an adequate growth in agricultural production in many Third World Countries, especially in Africa (Ehlers 1984). In fact, due to violent conflicts and problems of national economies, agricultural production in Africa actually dropped over the last few decades, in some countries up to 15 per cent and by 6 per cent over the whole region (Lawrence 1986: 1). Many African countries are dependent on subsidized food imports from overseas nowadays.

While there are many studies on population growth comparing the growth rates of states, there is very little information on growth rates in pastoral populations and on demographic growth in relation to specific production systems. Although it is generally noted that an understanding of demographic processes is essential for a comprehensive description of pastoral economies, there are as yet few studies devoted to demography in pastoral societies. A first set of studies suggests a variety of demographic patterns in pastoral societies and a variable impact on local resources. There is no overall pattern of pastoral demographics - as there is no pattern for forager or farmer demographics. The population of the Ngorongoro Maasai rose constantly over the last two decades: at the same time the ratio of livestock per person decreased massively, making the reliance on pastoralism an ever more scanty affair.     However, not all pastoral populations grow at the same rate. The pastoral Samburu apparently attained higher growth rates than the pastoral Rendille. The differential growth rates are connected to different growth rates in camel and cattle herds: while the camel herding Rendille adjusted their population growth to the slow growing camel herds, the Samburu could grow quicker due to the rapid growth of cattle herds. It is suggested that pastoral populations like the Rendille intentionally control their own fertility in order to adapt the growth of the human population to growth rates of the resources. In general it is assumed that sedentary populations grow quicker than agricultural groups. However, nomadic Turkana had higher birth rates than Turkana settled on agricultural projects. Among the Borana and the Gabbra of northern Kenya, infanticide, post-partem taboos and culturally prescribed delayed marriages of women had a sizable impact on population and subsequently sets a limit on the rate of population growth.

The study group analysed demographic trends in two pastoral populations: the Pokot of Kenya and the Himba of Namibia. The demographic development of Himba and Pokot is very different. While the Pokot are a rapidly growing population the Himba are a very slow growing one. The growth rate for the Pokot established on the basis of various historical censuses matches with the growth rate deduced from figures on intrinsic fertility, i.e. intrinsic growth explains for the total growth rate. In stark contrast to that population development in Kaokoland and amongst the Himba has been very different. While the Himba population grew only very gradually, the total population of Kaokoland grew more rapidly, especially so after the civil war in Angola started in the middle of the 1970s.

Figures on the intrinsic growth of the Himba community suggests an annual growth rate of 0,08 per cent which is modest in comparison to neighbouring agricultural populations and worldwide figures. In contrast the 2.4 per cent growth rate of the Pokot is rather high for a pastoral population. The completed fertility rate for Pokot women was at 4,7 while it was at 3,2 for Himba women. Only the inter-birth intervalls were fairly close to each other: 3,4 among the Himba and 3,3 among the Pokot.

This contrast is not explainable by cultural preferences; Himba like children as much as Pokot do: at this stage the high prevalence of STDs (sexually transmitted diseases) amongst Himba must be seen as a major cause for the difference. STDs were not treated in Kaokoland until the first small hospital was opened in Orumana in the 1960s. Obviously this hospital did not care intensively for STDs. In stark contrast to that neighbouring Ovamboland, more populous and from the beginning of colonialism regarded as the most important labour reservoir, received medical inistutions already in the 1920s. Since the middle of the 1920s regular anti-gonorrhea activities took place with about 1500 to 2500 people being treated per year. However, there are some cultural features which may add to this explanation. In Pokot society everything seems to be set on rapid growth. Infertility is seen as the greatest misfortune a person can meet. Infertile women and men become social outsiders. There are numerous rituals that are meant to insure the fertility of humans and animals. Women and men want to get as many children as possible. The high rate of polygyny is partially explained with the wish of wealthy household heads to increase their number of children. Throughout the last century Pokot men married Turkana, Tugen, Marakwet and Samburu women; but it was very rare that a Pokot woman married an outsider. On the other hand the Himba do not seem to put so much emphasis on population growth. Infertile people are not scorned and may participate in any ritual just as other people do. Infertility as such is not a reason for divorce. Himba society never expanded through incorporation of outsiders.

Different growth rates of the population condition different degrees of pressure on basic resources. The ratio of people to livestock gradually declined amongst the Pokot. While the ratio was above 1:10 during the first part of this century, it declined to a low of 1:2 and even 1:1. These figures give a strong indication of the vulnerablity of the Pokot pastoral system. Not only did the total number of livestock in the area greatly shrink, but there is ample evidence for a decrease of wealth differences. Very rich herders with herds of more than 200 cattle are extremely rare in Kaokoland and in the sample of herders that I worked with there was nobody. Listening to oral testimonies and screening archival files, there is little doubt that such wealthy herders existed during the first half of the century. The decrease of livestock also points to the fact that livestock in the entire system of pastoral production may have changed over the years. One may hypothesize an intensified care for animals as the pastoral sector is almost over-supplied with labour. Demographic growth among the Himba has been slow and has not exerted such an intense pressure on the resource base. While livestock ratios were roughly at 1:5 earlier this century, this ratio went up and reached values above 1:10 around the middle of the century. Due to droughts, which caused excessive mortalities in livestock, ratios decreased repeatedly and recovered swiftly thereafter. Towards the end of this century rates again reached a value of 1:5. The different trends of demographic growth and of man/resource, ratios had a spin off effect in other fields. Rapid population growth necessitates increased production which - under the condition that productive strategies are not changed - in turn accelerates degradation.