COLIN CLARK 
per year, or one-twelfth of a cow’s yield) thus could also be 
produced on a little over 400 square metres. 
Grassland in the high rainfall tropics is shown to be capable, 
when fertilized, of producing three times as much as the best 
temperate grassland. Such land is also capable of producing 
three cereal or leguminous crops per year, if properly fertilized. 
There have even been cases of fertilized tropical grasslands 
producing at the rate of 80 tons dry weight per hectare per year, 
or more than five times the maximum temperate climate yield. 
Our land requirements, therefore, using the best agricultural 
methods now available—though great further improvements 
will be possible—in a temperate climate, not for a subsistence 
diet, but for our accustomed rich diet, may be expressed as 
follows: 
Square metres/person 
Cereals, sugar, etc. 500 
45 kg. pig and poultry meat 500 
45 kg. beef and mutton 400 
250 kg. milk 400 
1800 or 55 persons/hectare 
Excluding the wet tropics, defined as lands with a hot climate 
and rain available for most or all of the year, the world has 
the equivalent of 6,660 million hectares of good agricultural 
land!3, This does not include land which has to be made 
productive by irrigation, but only the land naturally capable of 
agriculture, including, in some parts of the world, poor soils 
requiring considerable fertilization. Where the land is dry for a 
substantial part of the year, as in much of India, or has exces- 
sively long winters, as in northern Sweden, a proportion of its 
productive capacity is discounted in compiling this total; thus, 
a hectare of the coldest farm lands in Scandinavia has been 
entered as only half a hectare; a hectare of grazing land in 
Australia as only one-thirtieth of a hectare. 
The wet tropics contain 510 million hectares of potential 
agricultural land—158 million each in Africa and Latin 
America, the remainder in southeast Asia—equivalent to 
34 
