92 THE FUTURE OF ARID LANDS 
TABLE 1 
Sian Minimum Maximum 
Annual Average Rainfall " Depth, om Depth, 
by period ear san an ea an/ian 
I year 1946 62 1921 372 
2 consecutive years 1945-46 67 1905-06 333 
5 consecutive years 1943-47 II§ Ig18—22 263 
IO consecutive years 1938-47 143 1905-14 229 
20 consecutive years 1933-52 180 1903-22 224 
50 consecutive years General average Igo1I-52, 197 m/m. 
paring them with the rainfall during the period 1890-1905 (10). 
The author of this study has inferred from it that the period 
1736-go was clearly more rainy than the present period. Despite 
all the reservations that one can have on the methods followed by 
Ginestous, one 1s struck by the fact that the historical documents 
actually make no mention of famines in the eighteenth century 
(2), but do mention, on the contrary, abundant rains and harvests. 
One can proceed no farther in Tunisia because there is a lack of 
trees to observe, but the method may be developed in other 
countries of the arid zone. Very old trees exist even in the center 
of the Sahara. 
The ensemble of historical and archaeological studies argues in 
favor of a great stability of climate. For Tunisia, this conclusion 
was drawn from numerous studies based on the examination of 
ruins, of Roman and Arab water works, of historical texts, of the 
constancy of methods of cultivation and types of plants raised, 
and finally of the exceptional character of the two four-year 
periods cited above. The same conclusion was arrived at in Israel 
(a8) armel iva Ikachia, (a). 
So the rainfall seems to have remained the same since antiquity, 
with the exception of variations of the same kind as those that 
we noticed at the present time. Can these variations be foreseen? 
It must be noted in this respect that a dry year, even an ex- 
ceptional one, does not result in famine nor does it constitute an 
economic catastrophe, unless it is one of a group of consecutive 
dry years extending over a vast territory. It is important to fore- 
