386 THE FUTURE OF ARID LANDS 
gated for cultivation, and they now harbor locust populations 
which otherwise would not have been able to survive without 
migration. Irrigated crops in the southern United States, Argen- 
tina, and Central Asia suffer from grasshoppers whose existence 
in these arid lands was made much easier by man. 
Development of Semi-Arid Lands 
This much too brief survey of the problem should be sufficient 
to show, first, how erroneous was the old belief that grasshopper 
and locust plagues are a feature of undeveloped lands and almost 
belong to the past. On the contrary, there is no doubt that the 
grasshopper plagues in semi-arid lands have been created by their 
much too rapid and thoughtless development, in the same way 
as the deterioration of soil and its erosion. Moreover, even now 
and even in the better developed semi-arid countries, the prob- 
lem tends to become more and more acute, and ever increasing 
efforts and expenditure are required to reduce losses from grass- 
hoppers by chemical methods, which alone will never provide a 
satisfactory solution. This experience of the already developed 
semi-arid countries should serve as a warning to others where 
schemes for the opening of vast new semi-arid lands are being 
considered. 
Development of Arid Lands 
The development of the truly arid lands is only beginning, but 
we have seen that it is almost certain to benefit such inhabitants 
of the desert as locusts. Their life is full of hazards at present, 
but should the ‘‘islands’” of cultivation in the desert become 
large and numerous, they would save many a nomadic swarm 
from starvation and provide conditions in which local popula- 
tions of locusts could multiply. 
Even apart from encouraging locusts directly, cultivation of 
desert lands is certain to increase the risk of crop losses as a 
consequence of making more crops exposed to locust attack. 
All this does not mean, of course, that development of arid 
and semi-arid lands should be discouraged. My object is merely 
to draw attention to the need for taking into account its possible 
