CHAPTER FOUR





C. MAUREEN CUNNINGHAM





THE EFFECTS OF GLOBAL WARMING ON THE POPULATION, AGRICULTURE, AND 

EPIDEMIOLOGY TRANSITIONS IN THE SOUTH SAHEL REGION OF AFRICA





        The Sahel cuts a swath across West Africa from Senegal through 

Chad.  It is the zone just South of the Sahara desert, and is the area 

into which the Sahara desert shifts in its movements southward (See Map 

following).  Due to expansion and contraction of the Sahara (Tucker et 

al., 1990), it is difficult to define where the southern border of the 

Sahel falls.  The Sahel is the major transition zone between the more 

humid tropics to the south characterized by two dry seasons and two 

growing seasons and the hot, dry, desert to the north. The southern part 

of the Sahel and the northern part of the humid tropics is the area  

under study made up of Northern Benin, Southern Niger, and Burkina Faso, 

called here the South Sahel region (see Map following). While there are 

some sociological and cultural differences in the different parts of the 

South Sahel region, the climate, lifestyles and modes of agricultural 

production are very similar throughout.

        The region is labeled the Sudano-Guinean Climate Zone (Martyn, 

1992).  It is dry and hot, with three identifiable seasons:  The first, 

called the Harmattan, is dry and relatively cool, the second is hot and 

relatively humid, and the third is rainy and hot.   Rainfall is low and 

unreliable compared to the more humid south where there are two 

relatively stable growing seasons per year (Simsik, 1993).

        The people living in the South Sahel region are agriculturists 

for the most part, depending on the one annual growing season to provide 

the bulk of their income and nutritional subsistence each year.  

Agricultural labor is accomplished with  simple tools such as the short 

handled hoe and the machete (Simsik, 1993).  With only these inputs to 

production, labor is of high importance.  The land area under cultivation 

is fairly small for any given person or family due to the intensity of 

labor necessary to produce crops.  Most farming is of subsistence crops 

such as millet and sorghum and some commercial crops such as cotton and 

groundnuts for export (Simsik, 1993, United Nations, 1994).     It is 

important to study global warming in the South Sahel region in terms of 

the population-environment dynamic in order to develop policies which can 

be implemented by the governments involved to mitigate the societal and 

environmental problems that global warming 

exacerbates.  The region has a highly constrained ecosystem.  According 

to Agbo et al, "The greater number of types of ecosystem constraints 

involved and the greater degree of constraint of these components, the 

more tightly linked the population-environment dynamic will be in any 

region (Agbo et al., 1993).  Tight linkages between population and 

environment mean that the more the environment changes, the more the 

population will be affected.  As the population changes (for example 

grows larger), the environment is highly affected (Agbo et al., 1993).  

Population and environment are inextricably linked, and must be 

considered in terms of each other before any policy changes can 

positively impact a constrained ecosystem.

        There are three types of ecological constraints that are apparent 

in the South Sahel region.  The first is geographical.  The South Sahel 

is geographically constrained in terms of water availability which 

dictates where people can survive.  The second type of constraint is 

ecological.  Poor soils mark the entire region, limiting the number of 

people who can sustain themselves in any given area.  Finally, there are 

economic constraints.  These include the populations dependence on 

subsistence agriculture, as well as their dependence on the fluctuating 

global market economy over which the local people have virtually no 

control for the sale of their cash crops (adapted from Agbo et al, 

1993).  

        Interactions between the population and the environment are not 

the only ones that affect the region.  In the world today, action or lack 

of action in one region can have a strong impact on other regions of the 

world.  An important case in point is global climate change.  The people 

and production of the South Sahel Region have not contributed a great 

deal to anthropogenic (human generated) climate change, yet global 

warming (a more simple term for anthropogenic climate change) may 

strongly change the environment in the region (Glanz, 1992).  Through the 

environment, global warming may influence other sectors of the region 

such as the population, health, and agriculture. 

        An appropriate way to look at the population-environment dynamic 

is through the transitions framework, developed by Dr. William Drake.  In 

the physical world, there are a variety of factors which affect every 

sector.  Transition theory makes explicit the interdependence of sectors, 

and is an attempt to look at change in a realistic yet manageable fashion 

(Drake, 1993)  

        Given that the world is made up of interrelationships across 

regions and within them, it is admittedly impossible to foresee all 

aspects of change in any sector.  Transition theory gives a framework for 

examining some of the aspects that cause change.  There is a whole family 

of transitions which includes the environmental and population 

transitions, as well as the agricultural, forestry, urbanization, 

epidemiological and other transitions.  A transition can usually be 

broken down into many others, depending on the specificity of the study.  

For example, one could study the population transition alone, or one 

could break it down to investigate the fertility transition as distinct 

from the mortality transition.  A transition means a change from one 

state to another, but does not imply either positive or negative change.  

In transition theory, change is from some point of stability to another 

point of stability which may be entirely different from the first.  For 

example, in marginal lands where scrub-cover is the stable state at 

present, the stable state following a forestry transition may be a 

desert.  Transitions occur similarly on many different scales, both 

temporally and spatially.  Transitions can and do interact with each 

other and affect each other.  From a policy perspective, it is the timing 

and speed of transitions that may be realistically possible to change, 

not the actual occurrence of any given transition (Drake, 1993).

        In general ways such as those stated above, transitions are 

similar across space and time, but at a local level, transitions occur in 

very different ways and are changed by a myriad of local occurrences.  In 

this paper, I will investigate three of the transitions occurring in the 

South Sahel, specifically the population transition, the agricultural 

transition, and the epidemiological transition.  I will look at the 

position of the South Sahel in each transition now, and then look at how 

global warming may affect the progression of the transition, and finally 

how the governments involved can positively influence the timing and 

speed of the transitions to ease their negative effects on the 

population.  

        Since data for the South Sahel specifically has not been gathered 

or calculated, I will use data from the three countries which each 

include part of the South Sahel.  While such an amalgamation is not an 

exact proxy for the South Sahel, given the similarities of the region, an 

approximate average of the three countries rates and figures paints a 

close picture to what data collected exclusively for the South Sahel 

would illustrate.  Where possible I include data for all three 

countries.  Occasionally only one or two countries data is available for 

illustration and that is used as a rough guess of the South Sahels data 

itself.  



GLOBAL WARMING

        Leaders of  less developed countries often see the problem of 

climate change as far out of their realm of control.  Understandably, 

climate change is pushed to the side as something which, if it does 

occur, is seen as so far in the future, and is as yet so unpredictable 

that it is not necessary or possible to deal with at this time (Glanz, 

1992).  It is true that the effects of global warming on a regional scale 

are unclear.  It is also true that developing countries have not been a 

primary producer of greenhouse gasses (those gases which cause global 

warming to occur) (Glanz, 1990).  But climate change, whether human in 

origin or purely natural, highly affects those peoples who live closely 

linked to the environment (Agbo et al., 1993).  Subsistence farmers, the 

bulk of the people in the South Sahel as well as much of the developing 

world, are harder hit by climate change of any type than are populations 

that have more of a buffer between the environment and themselves.  This 

is true whether that buffer is a personal savings account or improved 

technology which allows high levels of agricultural production in the 

face of climatic variation.  Policy makers in Benin, Niger, and Burkina 

Faso, as well as other developing countries need to address the possible 

impacts of global warming before they negatively affect their people.

        The Intergovernmental Panel on Climate Change (IPCC) is made up 

of researchers from all over the world working with the UN to study the 

causes, effects, and possible future scenarios of climate change.  

According to the IPCC, climate change due to human activity is definitely 

occurring globally.  Anthropogenic climate change is caused by the 

emission of  greenhouse gasses (GHGs) which include carbon dioxide, 

methane, nitrous oxide, halocarbons, and hydroflourocarbons.  The most 

important of these is carbon dioxide (CO2) due to its high concentration 

and rate of increase in the atmosphere.  Greenhouse gasses are produced 

through industrial production and transportation that depend on the 

combustion of fossil fuels as well as land use conversion (IPCC Draft 

Report, 1995).  Once GHGs are released into the atmosphere, they act in 

much the same way as a greenhouse.  They trap some of the radiation 

coming from the earth in the earths atmosphere and do not allow the 

earths natural cooling process to work as strongly as it would without 

the high levels of GHGs (Benarde, 1992).

        As of yet, the full effects of climate change are not known.  A 

way to look at the possible effects is to set up modeling situations in 

which many variables at different levels are factored in, such as the 

rate of GHG production into the future (Benarde, 1992).  Commonly 

accepted models point to a global temperature increase of anywhere from 

1.5-4.5 degrees Celsius eventually (Schneider, 1994), and 1-3.5 degrees 

Celsius by the end of the next century (IPCC Draft Report, 1995).  

According to the IPCC, In all cases the average rate of warming would 

probably be greater than any seen in the last 10,000 years, but the 

actual annual to decadanal changes would include considerable natural 

variability (IPCC draft report, 1995).  Experts on climate agree that 

temperature change is likely to be greater at the poles than at the 

equator (IPCC DRAFT Report, 1995).  The IPCC projects a rise in sea level 

from 15-95 cm. by the year 2100 due to thermal expansion of the oceans 

and the melting of some of the earths water currently contained in ice.  

Modeling on precipitation is less precise than on temperature and sea 

level rise.  Some models predict more severe droughts and floods, some 

models predict more severe precipitation events such as increased cyclone 

possibilities (IPCC draft report, 1995).

        While global effects of some degree are inevitable due to 

anthropogenic climate change, regional effects are highly uncertain to 

date, and the smaller the region of interest, the less certain the 

effects become (Stephen Schneider, personal communication).  The IPCC 

predicted in 1990 that in the Sahel, the temperature will eventually 

increase from 1 to 3 degrees Celsius.  Area mean precipitation will 

increase and area mean soil moisture will decrease in the hot season 

(Suliman, 1990).  Soil moisture, as controlled by evapotranspiration, is 

extremely important--regardless of the amount of rainfall.  If the water 

in the soil is evaporating at a relatively greater rate than the rate of 

increased rainfall, there is less water for plants to use for growth, a 

matter of vital importance to farmers depending on rain fed agriculture 

as are virtually all the farmers of the South Sahel region.

        In looking at the temperature data available for the South Sahel 

region which is collected and made available by the National 

Oceanographic and Atmospheric Agency (NOAA) some interesting, although 

inconclusive, evidence is apparent (see Figures 1-4).  I chose four sites 

at which data is available for at least 50 years prior to the latest year 

of data available (usually 1992), and which correspond to my area of 

study.  The four sites I chose are Natitingou and Kandi in Benin, Fada 

NGourma in Burkina Faso, and Niamey in Niger (see Map near front).  Data 

for some of the sites went back further than what is included but was 

left out because there were periods of several years with no data 

whatsoever.  For those years in which data is available, but in which not 

every month is available at a given site, the year is not included for 

that site only.  

        When the years of complete data are graphed (represented by the 

black diamonds in Figures 1-4), a striking aspect of annual temperature 

is apparent.  Obviously, even without the effects of anthropogenic 

climate change mean annual temperature varies widely at all four 

locations. By fitting a simple linear curve to the data available for 

each location, a surprising aspect becomes clear:  In all cases except 

for Niamey, the temperature appears to be declining, albeit very slowly,  

over time.  If, however, a linear curve is fit to the data since 1960, in 

all cases except for Natitingou, temperature is rising.  Even in the case 

of Natitingou, temperature since 1960 is falling less quickly than 

temperature for all the years with data available.  Since the early 1960s 

has been identified as the time that global warming may have begun to 

visibly affect global temperature, fitting the curves from 10 years prior 

to that time onwards helps ensure that  natural variation in annual 

climate alone is not causing the trends that appear when a linear curve 

is fitted to the data.  When these graphs are made fitting the curve from 

1970 onward, temperature is increasing for each of the four cases.  



Figure 1





Figure 2

 



Figure 3

 



Figure 4

 

Figure 5

THE DEMOGRAPHIC TRANSITION
     According to demographic theory (Coale, 1974), the demographic  transition as seen thus far has four stages.  In the pre-transition  stage, birth rates are very high, but are counterbalanced by high death  rates.  The overall effect is a population with little or no growth.  In  the early stage of the transition, death rates fall due to public health  and medical improvements in the population.  Birth rates remain high and  a population explosion occurs.  In the late stages of the transitions,  births begin to fall, and although they still exceed deaths and  population continues to rise, the rate of increase is slow.  Finally in  the fourth stage called the post-transition period, the birth rate falls  to the point that it is roughly equal to the low death rate and the  population reaches a steady state of approximately zero population  growth.  This model is based on the experience of more developed  countries (Haub et al., 1994) where the  transition has occurred smoothly  and over a long period of time.  There the decrease in death rates  occurred slowly and was of endogenous (interior to the region) origin,  caused by a gradual increase in knowledge about health and medicine.   There was a lag in the fall of birth rates following the fall in death  rates, but not so great as to create a large degree of stress either on  the environment or on the population.
     The South Sahel region, and indeed much of Africa, is  experiencing a population transition much more violently and quickly than  the more developed regions did. The South Sahel is currently at the point  of change between the early and late stages of the transition.  Changes  to the death rate came relatively quickly (the early stage), beginning  around 1950 in the form of life-saving vaccinations and medical  technology provided in large part by international aid agencies (Haub et  al., 1994).
      Birth rates, on the other hand, have remained relatively  constant.  An amalgamation of the population growth for all three  countries in the South Sahel region gives a fair idea of what the rates  are, given the similarities between Northern Benin, Southern Niger and  Burkina Faso. At the present time, the crude birth rate (CBR) per 1000  people in the population per year in Benin is 48.09.  In Burkina Faso it  is 48.8, and in Niger it is 57.35, while the crude death rates (CDR) per  thousand people in the population per year is about one third of the  birth rates at 14.8, 18.19, and 22.44 respectively (CIA, 1995).  Since  the growth rate percent (minus migration) is equal to births minus deaths  divided by ten, the region has an overall growth rate percent of  approximately 3 (3.1 in Benin, 2.8 in Burkina, and 3.4 in Niger (World  Population Council, 1995).  This number may not seem very high, but  consider that a growth rate percent of three means that if the growth  rate remains unchanged, the number of people in the region will double in  only 20 years (see figure 6 below).

Figure 6

 

Figure 7

 

        By the year 2025, the population in the region will be 

approximately three times its present level.  Perhaps even more striking 

than the level of increase is the irrevocability of the increase.  Due to 

population momentum and the slow speed of decrease in the growth rate, 

population will continue to climb throughout the foreseeable future even 

though growth rates are projected to begin falling in this decade.  In 

the South Sahel region, population momentum rests to a large degree on 

the age distribution of the population.  Nearly half of the population at 

the present time is under the age of 15.  Thus, a huge majority of the 

population is in, or will be moving into, their reproductive ages within 

the next 15 years.  Even if the number of children born per woman fell 

dramatically, the number of people having children will keep the  

population growth rate high (see Figure 7).

Figure 8



 

        

        The effects of population density increase on the South Sahel 

region will be strongly felt.  Whereas at present the population density 

is about 40 per square kilometer (49 in Benin, 38 in Burkina, and 6 in 

Niger (World Population Council, 1995), under the present UN projections 

for future growth, the population density will increase to about 90 per 

kilometer by the year 2025 even though population growth is falling (see 

Figure 8 below).  Nigers population density is very low in the mostly 

empty upper portion of the country.  The bulk of its population is in the 

South Sahel region where farming is difficult but possible, unlike the 

desertic North.  A population density of 40 per square kilometer is not 

terribly high, but for a subsistence farmer with low crop yields, it may 

be close to what the land can bear and still provide sustenance for its 

inhabitants.  Thus, the population density, while low compared to some 

regions is high for the South Sahel region due to the constrained 

ecosystem and the modes of agricultural production.  People are not 

acting to limit their fertility general-

ly in the South Sahel Region.   Contraceptive use levels by women are

very low:  approximately 9 percent  of Benins women ever uses contraceptives,

and about 1 percent of Nigers  and Burkinas women are contraceptive users.

AGRICULTURAL TRANSITION
       The agricultural transition has followed a trajectory similar to  the worldwide population transition.  For many centuries, agricultural  production kept pace with human population (Drake, 1993).  There were  periods of famine due to war, drought or other climatological disasters,  but on a large scale, human populations were able to produce enough to  feed themselves.  Increases in agricultural production came through the  increase of the amount of land under cultivation, and improved methods of  production.  Drake identifies the shift in increase from amount of land  under cultivation to improvements in productivity per hectare as the  beginning of the agricultural transition (Drake, 1993).  The transition  includes the period of increasing returns on inputs into fixed land  holdings, and eventually reaches a stable point when a given area of land  cannot profitably be made to produce more output.  According to Drake,  the shift from size to intensity is especially remarkable at the  individual farmer or family level at which the amount of land owned or  open to use may be fixed, leaving a farmer only one alternative to  increase production:  increased growth intensity.  If increased intensity  does not occur, but population continues to increase, rural to urban  migration will occur, giving those who remain on the land more area to  cultivate.
     The South Sahel region is at the early stages of this  transition.  The vast majority of people in the region are farmers (over  90% of the labor force in 2 of the 3 countries involved are  agriculturists (CIA, 1995), and almost all farmers work on small,  family-run farms.  Some cash crops, mostly cotton, are produced (CIA,  1995).  Food crops are varied and include:  sorghum, millet, cassava,  rice, tubers, and others to a lesser degree (UN, 1994, and CIA, 1995).   In general, women grow food crops and men grow both food crops and cash  crops.  Agricultural production is accomplished using traditional methods  and only the most simple of tools:  short handled hoes, shovels, and  machetes.  Agricultural production is highly labor intensive, and yields  are low.  For example, in Niger, the profit in terms of food produced per  hectare of arable land is at about $120 in constant US 1985 dollars per  year (WRD, 1995).  Considering that a family with 4 people working can  cultivate slightly more than 4 hectares of land on average (this  statistic is for Tanougou in northern Benin, Agbo, 1993), the amount of  food or profits produced is very low.  Most land is broken into small  plots of less than a hectare to one or two hectares, with one family  farming several plots.  Little in the way of technological advances have  been brought in.  Fertilizers and pesticides are used, but due to their  high cost they are not used in the recommended amounts.  Some livestock  is raised, mostly for family consumption, except for Burkina Faso where a  substantial number of cattle and sheep are raised for sale (UN, 1994, and  CIA, 1995).
          The soils of the region are relatively poor and non-productive.   In the past, this was a manageable problem in that the population in any  given area was low enough to allow long periods of fallow between   periods of production which gave the land the opportunity to replenish  its nutrient content.  As population increases and more pressure is  applied to the already constrained ecosystem-system, periods of fallow  are decreased out of a necessity to use the land for food production.   Land that used to be left fallow for a decade or more in between each  several year period of use is now only being left fallow for 4 or five  years.  Another common practice which decreases the fertility of the soil  is burning off the ground cover which grows up in times of fallow and  between harvests.  In a region of no winter to naturally break the insect  and pest cycle, burning the fields helps to accomplish this vital task  for production (Schneider, personal communication), but much of the  organic matter on the land is in a sense wasted by being burnt off  instead of being used to enrich the soil.  Fire also destroys any  unprotected trees which serves to increase the shortage of fuel wood in  the area (Agbo, 1993).  Finally, fire leaves the land open to wind and  water erosion until substantial plant cover is replenished.  Some  fertilizers are used in an effort to substitute for the loss of soil  fertility, but for the most part these inputs are too expensive for  families to afford (Simsik) or unavailable to be used correctly. When  they are used, fertilizers have their own long term debilitating effects  on the soil which necessitates ever greater inputs of fertilizer .
        Shortening fallow periods and field burning is impoverishing the  soil and ever decreasing yields per hectare.  This creates the need to  try to cultivate even more land to produce enough to survive.  The need  for labor to work the increasing landholdings leads to an increased need  for children.  More children serve to increase the pressures on the land,  both through need for agricultural production and need for the fuel wood  and other resources that the land provides.  This cycle will continue to  reproduce itself and expand until the population can feed itself without  relying on the practices that serve to keep the cycle in motion.

EPIDEMIOLOGICAL TRANSITION

The basic epidemiological transition is highly related to both the 

agricultural and demographic transitions described above.  In the early 

stages of the transition, most death is caused by infectious disease and 

malnutrition related disease (Drake, 1993, and Dewey, 1986).  There is a 

high probability that any individual will contract a mortal disease and 

die before they reach old age.  As public health and sanitation measures 

take effect, such as clean water provision and food safety standards, the 

first stage of the transition begins.  Infectious disease and 

malnutrition related disease take fewer young lives, and people begin to 

live longer on average.  As medical technology improves, vaccinations are 

administered against many infectious diseases, and  food becomes more and 

more secure due to agricultural improvements.  Living into old age 

becomes the norm. Death is no longer caused by infection or malnutrition 

for the most part, instead it is due to a whole host of degenerative 

diseases such as heart disease and cancer.  Degenerative diseases existed 

previous to this stage, but since they affect the elderly much more often 

than the young, they were rarely seen.  This last stage has been reached 

in much of the more developed world, and life expectancies at birth have 

soared into the 70 and 80 year ranges (Population Reference Bureau, Inc., 

1995).  The majority of people in the West live into their retirement 

years and experience one or more of the degenerative diseases from which 

they eventually die (Drake, 1993, and Dewey, 1986).

Figure 9

 

        In the South Sahel region, the transition is underway to some 

extent, but it has come about in a very different manner than it did in 

the West.  Instead of a decrease in illness and death at young ages 

beginning with public health measures as was seen in the West, the 

initial decrease in death rates in the South Sahel came primarily from 

vaccinations and improved medical technology.  For example, in the South 

Sahel region today, only about 35% of the rural population has access to 

safe drinking water (43% in Benin, 31% in Burkina Faso, and 32% in Niger) 

(WRD, 1995).  Sanitation services, such as latrines are in even shorter 

supply with approximately 12% of the population having access to them (5% 

in Burkina Faso, 4% in Niger, and 35% in Benin).  On the other hand, a 

large proportion of infants are immunized now against the childhood 

killers including tuberculosis, diphtheria, polio, and measles (WRD, 

1995).  Thanks to the World Health Organization, small pox has been wiped 

out.  Antibiotics are now available to those who can get to health care 

facilities.  Access to medical facilities is low however, with overall 

access to a clinic or hospital at less than 50% (WRD, 1995). 

        The effect of the changes in health care and medical services has 

increased the life expectancy dramatically since international aid 

agencies began working in earnest in the 1950s (see Figure 9 above), but 

in all three countries of the South Sahel, life expectancy is still quite 

low by more developed countries standards.  Since life expectancy is a 

measure of the average age at death, it is also an indicator of general 

ages of death across a population.  A low life expectancy such as that 

seen in the South Sahel Region is indicative of deaths due to infectious 

disease and malnutrition related disease because it shows us that a large 

percentage of the population is dying before they reach old age when 

degenerative diseases generally set in.  Infant mortality rates also can 

be used as rough indicators for death rates across all age groups.  In a 

region with high infant mortality, there is likely to be high death rates 

across all age groups, indicating high death rates from infectious and 

malnutritional diseases.  Infant mortality has declined somewhat in the 

South Sahel mostly due to improvements in vaccinations and medical 

technology available, but it remains very high, at 109 per thousand live 

births annually for Benin, 134 per thousand for Niger, and 137 per 

thousand for Burkina Faso (WHO, 1991).

Figure 10

 

        Due to a lack of reporting, morbidity rates (rates of illness) 

are not well known for most of the world.  A study was carried out in 

Burkina Faso which indicates that the leading causes of visits to health 

clinics and hospitals for children under five in that country are, in 

order of rates, malaria, diarrheal disease, respiratory infection, and 

malnutrition related disease (See figure 10) (Konate et al., 1994).  This 

information roughly corresponds to the World Banks assessment of 

mortality causes for children in demographically developing countries 

(World Bank, 1993).  Children under five bear a large percentage of the 

burden of communicable disease.  In Sub-Saharan Africa, when infectious 

disease occurs, 63.5% of the time it is to a child under five;  32.1% of 

non-communicable disease (including malnutrition) is borne by children 

under five.  The corresponding figures for children in the more developed 

countries of the world are: 29.3% of communicable disease and only 4.3% 

of non-communicable disease (World Bank, 1993).  

        The overall infectious disease rate for people of all ages is 

extremely high in the developing world. The daily adjusted life years 

lost (DALYs) due to any given disease or adverse situation (such as 

malaria or lack of clean water) is a useful measurement of disease 

rates.  It takes into account both loss of life and loss of health while 

alive.  In Sub-Saharan Africa, the rate of DALYs lost to people of all 

age groups due to infectious disease is estimated at 408.7 per 1000 

people.  The corresponding rate due to infectious disease in the more 

developed world is only 11.4 DALYs lost per 1000.  On the other hand, in 

the more developed world the non-communicable disease rate is closer to 

that of sub-saharan Africa at 92 DALYs lost per thousand people.  

Sub-Saharan Africas non-communicable disease rate is 111.4 DALYs lost per 

1000 people.  This rate is slightly higher than in the more developed 

world, but it is apparent from these figures that proportionally, the 

vast majority of disease burden is caused by infectious disease in 

Sub-Saharan Africa, while the majority in the more developed countries is 

caused by non-communicable, degenerative disease.  

        The epidemiology and agricultural transitions include a change 

from food production for individual use to crop production for sale.  As 

productivity increases, a family can grow more than they themselves 

need.  Selling the excess production, or growing strictly cash crops, is 

a way to save what is produced and create a buffer against times of 

famine or hardship (Dewey, 1986).  Such saving is virtually impossible in 

a purely subsistence farming situation for longer than the year or so 

that excess food can be conserved.  This transition can be enforced by 

the government by the need to pay taxes or the need to have money 

available for other things such as school fees and transportation.  

        Once farmers move from purely subsistence farming to some 

subsistence and some market crops, food consumption is no longer 

equivalent to what is produced.  A movement to cash crops takes control 

of productivity, in terms of profit, out of the families hands and puts 

it into the markets.  For farmers with large and highly productive 

landholdings, this change means more luxury and diversity of diet, but 

for a marginal farmer the switch can lead to a decrease in nutritional 

intake if the farming family does not make enough money to purchase 

adequate food (Dewey, 1986).  Often the most fertile land is converted to 

cash crop use, leaving the more marginal land on which to produce food 

crops for family consumption.  In periods of low rainfall or other 

climatic catastrophe, those marginal lands produce little to nothing.  

The more fertile lands may still be made to produce crops, although to a 

lesser extent than in high rainfall years, but money has many uses 

besides food purchases.  Income from the sale of these crops may be used 

up before food is gone for other things such as paying taxes and school 

fees.  Over time, if a farming family is successful and the market 

remains high for their cash crops, the savings lead to the ability to 

increase either holdings or intensity of farming.  The increase leads to 

more savings and more increase.  This cycle, where it is possible, can 

lead to smaller farmers being pushed out because they cannot compete with 

the higher technology production of the neighboring farmers who can 

afford to sell their products for less (Dewey, 1986).  Rural to urban 

migration is the result, as we have seen in the United States.

        The South Sahel region is at present in the very early stages of 

this part of the transition.  Some cash crops are grown, mostly cotton, 

but, as are so many developing world producers, the ability to make 

profits is at the mercy of the international market.  Farmers frequently 

turn their best land over to cotton growth, with the idea of including it 

in their regular crop rotations.  Despite the high nutrient use of cotton 

plants (Simsik, 1993).  The soil becomes impoverished, and when it no 

longer will produce cotton in large quantities, it is turned back over to 

food crop production.

Figure 11

 

        Another result of a change to cash cropping is a decrease in the 

variety of what is grown (Dewey, 1986).  Evidence shows that very 

traditional cultures practicing subsistence farming generally have highly 

nutritional diets.  In the South Sahel, it appears that in years without 

drought the area is very close to food self-sufficient in terms of 

calories (see Figure 11).  In terms of nutrition there is a deficiency of 

vitamins and nutrients leading to high rates of malnutrition especially 

in children.  The prevalence of malnutrition for children under five is 

estimated at 46% in Burkina Faso, 49% in Niger, and 35% in Benin (World 

Bank, 1993).

        The epidemiological transition is underway, but due to limited 

access to care, agricultural constraints on good nutrition, and poor 

public health and sanitation, the transition is moving very slowly.







THE EFFECTS OF GLOBAL WARMING

        The demographic, epidemiologic, and agricultural transitions are 

all in progress in the South Sahel.  The timing and speed of all three 

are influenced by many factors, not least of all each other.  Perhaps 

already, but more likely in the near future, the rate of change in these 

transitions will begin to be influenced by the effects of anthropogenic 

climate change.  Although we are far from understanding all the effects 

global warming may have, when we look through the lens of the transition 

theory, we can predict some of the possible effects of human induced 

climate change.  In general, the most likely changes that global warming 

will bring are to exacerbate the negative effects of transitions already 

in progress.

        Perhaps the most direct change due to global warming will be in 

the agricultural transition.  In the South Sahel, rainfall amount and 

timing are vital to the growth of crops.  If global warming creates 

either more drought in the Sahel or increased volatility in precipitation 

as many predict (Suliman, 1990, Glanz, 1992, IPCC, 1995), the effect will 

be to increase the speed of the present circular trend of  decreasing 

production per hectare leading to the necessity to cultivate more land 

which in turn decreases the revitalizing fallow periods and impoverishes 

the soil further.  Increased drought and failed crops leave the earth 

open to wind and rain erosion when the rain does fall.  Erosion leads to 

increased desertification and impoverishment of soil fertility (WHO, 1990).

        Increased drought or precipitation volatility due to global 

warming may also lead to an increase in out-migration to urban areas due 

to a decrease in the ability to survive (Doos, 1994) in the South Sahel.  

The migration and urbanization transitions were not discussed in detail 

in this paper, but in brief,  if jobs or other sources of survival are 

not available in the urban centers where people of the South Sahel 

migrate, migration will serve only to swell the already existing problems 

of urban poverty and unemployment.

        Due to a decrease in the ability to produce at the lower 

latitudes, global warming is expected to necessitate a net increase in 

imports of cereals from 20-50% into the developing world (Fischer et al., 

1994).  The average decrease in crop yield of cereals due to global 

warming in the developing world is 10% (Fischer et al., 1994).  There is 

no reason to believe that the South Sahel region will be immune to these 

effects.  Policy options must be considered and implemented soon to try 

to avoid the negative agricultural effects global warming will cause.

        Global warming will indirectly effect the population transition.  

Population, poverty and environmental degradation are intertwined in a 

positive feedback loop (Dasgupta, 1993).  Global warming, through 

increased drought and volatility will add inputs into the loop in the 

form of worsening environmental conditions in the South Sahel.  As the 

environmental conditions worsen, people will need to have even more 

children to do the work necessary to survive.  As cereal production and 

other crop production decreases due to worsening agricultural conditions, 

the already tenuous state of nutrition of the South Sahel may worsen.  

There will be 40-300 million more people at risk for hunger due to 

climate change worldwide (Patz, 1995).  More malnutrition will lead to a 

higher risk of death, especially for young children.  As childhood 

mortality increases, people may feel that they must have more children to 

replace the children they have lost, to insure that a certain number of 

children survive, or to insure their own futures when they become too old 

to work (Dasgupta, 1995).  This trend is already occurring in the South 

Sahel.  Global warming will serve to increase the problem however and 

cause it to move forward at ever increasing rates.

        On another level, the worsening agricultural conditions due to 

global warming and the already occurring population dynamics will lead to 

increased poverty in the already poor region.  Increased poverty leads to 

fewer economic possibilities, and also less money to pay school fees.  

Parents in the South Sahel are extremely unlikely to send their girls to 

school if they cannot afford to enroll all their children.  Instead, boys 

go to school when the parents can afford to send any children at all.  

Since educational and economic opportunities for women tend to decrease 

fertility (Dasgupta, 1995), the opposite is also true-- where fewer women 

have such opportunities, fertility tends to increase.

        Global warming will not alter the path of the population 

transition as it is occurring now, but it may drastically increase the 

rate at which it is occurring.  Fertility rates are high at present, and 

will get higher still if the effects of global warming are not 

mitigated.  Policy changes cannot stop increases in population, but they 

can help to slow down the increases to give governments more time to 

provide infrastructure and services to the growing population.  

        The effects of global warming on the epidemiologic transition are 

in many ways tied to the population and agricultural transitions. 

According to the World Health Organization, global warming may directly 

increase health risks, especially for those people who have immature 

regulatory systems, such as  infants and young children, and those with 

failing cardiovascular, respiratory, renal, and other systems (WHO 

1990).  Increasing malnutrition is likely to occur, as described above.  

Malnutrition will also potentially increase due to less diversity in 

diets.  As the climate warms, and drought increases in the South Sahel, 

it is likely that some varieties of edible plants will not be able to 

adapt to the quickly changing climatic conditions.  Since the population 

of the South Sahel relies for the most part on the crops the people 

themselves can grow or gather, a decrease in varieties of crops may lead 

to a decrease in the nutritional value of the local diet.  

        Temperature is a major determinant in disease vector 

infectivity.  It affects replication, maturation, and length of 

infectivity of vectors (Patz, 1995).  Infectious disease rates are very 

likely to change due to changing climatic conditions.  While droughts are 

likely to intensify in the South Sahel, the amount of rainfall is 

expected to increase.  Increased evapotranspiration will remove a greater 

percentage of moisture from the soil, making both the earth drier and the 

humidity higher than at the present time.  Increased temperature and 

humidity tend to intensify the biting behavior of most insects (Patz, 

1995).  Since many infectious diseases in the South Sahel, most notably 

malaria, are passed through insect bites, it is likely that the rate of 

infection of such diseases will increase.

        Incubation periods for many viruses such as dengue fever, one of 

many arboviruses found in sub-saharan Africa, may decrease.  For example, 

it was found that at 30 degrees Celsius (a temperature experienced in all 

parts of the South Sahel during certain months) the incubation time for 

dengue fever is 12 days.  When the temperature is raised to 32-35 degrees 

Celsius as it may be with global warming, the incubation period is only 7 

days.  This effect alone leads to three times the transmission potential 

of dengue fever (Patz, 1995).

        With global warming, the relative burden of infectious disease on 

the population will probably increase from its already high levels in the 

South Sahel, as will the relative burden of malnutrition and malnutrition 

related disease.

        

POLICY CHANGES TO  MITIGATE THE NEGATIVE EFFECTS OF GLOBAL WARMING

        Since the exact effects and magnitude of effects of global 

warming on the South Sahel are not known, it is important that any policy 

implemented will also benefit the state and the people if global warming 

does not impact the South Sahel region as is expected.   In the South 

Sahel the most likely effects of global warming are to increase the speed 

and magnitude of the already occurring negative effects of transitions.   

No Regrets policies are relatively simple to envision in this case:  they 

must be policies which have the power, when implemented, to decrease the 

speed and magnitude of the most likely problems approaching.  They must 

also lead to positive changes for the environment and societies now.  By 

implementing No Regrets policies, the governments involved can provide 

the local population time for the international community and the 

domestic communities to discover effective, long term mitigative 

procedures.  If no policy is taken to mitigate global warming now, a very 

real possibility is that the state of the population and environment will 

deteriorate to such a great degree that long term solutions are 

impossible or are made extremely costly and difficult.  Since pertinent 

policy changes will all have some cost associated with them, it is 

necessary to chose policy changes carefully which could possibly be 

implemented by the governments involved.  The international communitys 

assistance in funding new policy implementation may be of extreme 

importance.  Also, since global warming is itself mostly a result of 

activities in the developing world, ideas such as debt swaps in return 

for policy implementation should not be ruled out.

        One of the gravest dangers that global warming poses to the South 

Sahel region is to decrease the populations ability to produce or 

purchase adequate amounts and types of food to achieve and maintain a 

healthy diet.  There are several fairly low cost policies which could be 

implemented to help alleviate this problem, while improving already low 

nutritional standards.  First, the governments involved should enlarge 

the agricultural extension services to the rural regions of the South 

Sahel.  Through these agencies, the states need to encourage the 

maintenance of food crops for local consumption as well as home gardens 

to improve both available calories and available nutrients no matter what 

the state of the international economy for cash crops is.  At the same 

time, extension agents should educate local farmers about the depletive 

effects of cotton production on the soil, not in an effort to cut out 

cash cropping, but instead to ensure that cultivators do not turn their 

most productive lands away from food crops.  Agricultural extension 

workers should train cultivators in methods of composting, interplanting, 

cropping of fallow lands with nitrogen fixing plants, and erosion 

reduction techniques to improve and maintain the fertility of the soil.  

Agriculture extension agents can also play a key role in introducing 

drought resistant varieties to the area.  Reforestation efforts should be 

supported by the extension offices.  Decreasing land cover opens up the 

land to greater degradation and loss of fertility, especially in times of 

drought when new growth is likely to be slow in covering and protecting 

the land.  Reforestation can also directly decrease the work load of the 

population by providing replenishable fuel wood to the population.

        Secondly, the local social centers, health and nutrition centers, 

and clinics should be enlarged and the staffs retrained.  The staff of 

these health related centers should become more actively involved in 

educating families about nutrition and maintaining a healthy diet using 

locally grown foods.  If possible it would be beneficial to expand both 

the health and agricultural sectors to a village level whereby each 

village had trained members who could both disseminate information to the 

public and receive new information and techniques from the government.  

One low cost alternative would be to train school teachers in health and 

agricultural techniques.  School teachers are respected members of the 

community in the South Sahel, and many people are willing to listen to 

them.  If they were trained well, they could act not only as teachers of 

children, but also leaders in new technology.

        Improving food security may of itself decrease population growth, 

but without more inputs it is doubtful that the effects on population 

would come quickly enough to help avoid the worst problems of 

overpopulation.  The governments of the South Sahel need to ensure that 

the population has access to contraceptive education as well as 

contraceptive methods.  Health clinic staff should be trained to provide 

both at low cost.  Men and women should be targeted for contraceptive 

education since both are of vital importance to decisions of fertility.

        Efforts should be made to improve educational and economic 

opportunities for women also since such opportunities have the effect of 

lowering fertility.  One way that this could be done would be to insist 

that development agencies provide equal opportunities to small business 

projects to both men and women.  Often, development projects target men 

because they are at liberty to take on new projects, while projects that 

target women must take children and family responsibilities into 

account.  Education for girls can be encouraged by lowering school fees 

and by educating the public, perhaps through school teachers, as to the 

advantages of educated women in terms of improved nutrition and health 

for the whole family and improved earning potentials.  

        The increase in the infectious disease burden that will be borne 

by the people of the South Sahel due to global warming can also be 

mitigated to some extent.  Again, education can play an economical and 

important role.  The local clinics and health centers, if properly 

staffed and trained can provide education and services to the populations 

to avoid and treat malaria and other infectious diseases.  Techniques to 

decrease the number of dengue fever and malaria carrying mosquitoes 

should also be disseminated through the clinics and village health 

centers.  The use of bed nets should be encouraged, especially for 

children, to prevent infection at night, and if possible should be 

provided at low cost.

        The people of the South Sahel must react to the threat of global 

warming.  They cannot do this however without the support of their 

governments through the provision of training, salary for staff, and 

supplying of local outreach offices.  By implementing these policies now, 

the governments involved can mitigate the potential negative effects of 

global warming.  At the same time, they can alleviate some of the 

problems already at play in the region.  If governments do not take 

action until they know the exact extent and form of damage due to global 

warming, the result will necessitate greater input to reverse the 

negative trends and not alleviate many of the problems of climate change.

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