12. Where crop farming and livestock production take place in the same ecological zone, the former is likely to be the activity to be more severely affected by drought in the shorter term - herds can be moved to areas where pasture production has not been affected to the same extent. Thus droughts occurring in areas occupied by crops and animals in Botswana have affected crop production more frequently (Jones, 1979). In the case of the Sahel, however, the crop farming areas occupy the higher rainfall zones to the south of the main pastoral areas which are subject to low levels and erratic distributions of rainfall within and between years. Since rainfall variability becomes more marked as one moves north and as rainfall totals decline, the pastoral sector has particularly been more prone to drought. Thus in the drought years of 1968 to 1973, it was pastoral zones of the northern Sahel which were especially badly hit, while many southern farming areas experienced very few drought-induced losses.
13. Account must be taken of the interaction between drought losses in the crop and livestock sectors for two reasons.
(i) Grain forms an important part of the pastoral diet even in normal times. In periods of drought, as herd productivity falls, herders come to rely even more heavily on grain for their food needs. Where both the livestock and farm sectors have been hit by drought, rising demand for grain by pastoralists is confronted by a drop in locally available supplies. Given the low elasticity of demand for grains, the increase in market demand from farmers and herders will result in a rapid escalation in prices. If drought has only hit the livestock sector, grain prices will be subject to much less upward pressure.
(ii) Farmers often own a number of livestock, which provide them with draft power and represent capital to be liquidated in times of need. Where drought has hit both the livestock and farming sectors, livestock prices will fall further and farmers will be faced with a greater fall in the value of their livestock assets. A few farmers may however benefit during a period of widespread drought if they are fortunate enough to have sufficient stocks of grain from previous harvests to invest in livestock purchases while relative grain to livestock prices are in their favour.