38 THE SHADOW OF THE WORLD’S FUTURE 
are relatively almost negligible in so far as they are to 
be counted on for the future supply of food-stuffs. 
The reason of this is that the statistics cover the more 
important countries, excepting those in the East. It 
would be clearly an exaggerated estimate were we to 
take the entire area as though it were similar to the 
portion statistically surveyed. Hence we are able to 
obtain a fairly correct idea of the world’s possible 
output of food-stuffs under existing conditions. We 
know at least that there are large areas that are 
practically worthless as far as food-supplies are con- 
cerned. 
As already pointed out, sea-mammals and fish will 
doubtless be drawn upon to a much greater extent 
than at present, not only as food-stuffs but also as 
fertilisers, as well as for general purposes. This, 
however, will not greatly alter the situation in respect 
of the world’s population-carrying power. For the 
purposes of this review of the whole question they need, 
perhaps, hardly be taken into account. The error of 
neglecting them cannot be very great, though it is not 
easy to estimate it with any precision. 
Inasmuch as the value, for the support of human 
life, of given areas of the earth’s land-surface differs 
greatly, we have to be guided not only by the per- 
centage of area available, but by the average-value of 
that area for food-production. The point may be 
illustrated, for example, by the very great differences 
in the yields of any staple crop, say, for example, wheat 
per acre; though, of course, it must be borne in mind 
that a particular crop may not be suitable to any 
given area. In bushels per acre the yield of wheat 
for different countries averaged in 1921 about as 
follows: —