MAN’S AGRICULTURAL NEEDS 29
following results for the subdivision of the earth’s landsurface
 into different classes of area: —

Total 52-5.—Unspecified 22-5, Non-productive 13-6,
Productive 16-4.
Productive 16-4.—Pastures 2-8, Shrubs o-2, Forest
7:3, Marsh 1-0, Arable 5-1.
Arable 5-1.—Grasses 0-79, Foods 0-39, Industrial
0-37, Seeds 0-02, Cereals 3-53.

Thus we may say that at the present time the arable
lands form only about one-tenth of the whole landsurface.
 The available area for the effective use of
human beings is thus seen to be very limited. In this
connection it is to be remarked that for different
countries the percentages available for food-crops varies
enormously. For example, while for Tunis it is only
0-1, for Czecho-Slovakia it is 43-1, for the whole
world it may be taken as somewhat under 8 per cent.
The productivity of various areas also differs as much
as seven times. 'Lhis matter will be dealt with more
fully in a later chapter.
A merely cursory glance at the above figures may at
first suggest that the possibilities of developing the
world’s agriculture are very great. Such an inference,
however, is not valid.
It would not, of course, be quite accurate to apply
the results of a statistical survey of only 46 per cent. of
the world’s surface to the entire area of that surface.
[t may nevertheless be taken as a rough guide. Applying
 it, we get the following results: —
Total. Productive. Non-productive. Not specified.
52-5 16-4 136 22-5 million square miles.
[000 21:2 25+Q 42+9 per cent.

How far the unspecified areas may be made to contribute
 to the productive or arable areas we are unable
to say. It is, however, clear that we should recard the