304 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1938 



deep cultivation, provided the topsoil is kept on top and the lower 

 layers are only stirred and broken up. 



This being premised, there is always a danger that if the cover of 

 vegetation is removed the soil itself will begin to move under the 

 action of either the wind or the rain. Rarely do we see these actions 

 at work on a large scale in England; the climatic conditions are not 

 favorable, for our rainfall is gentle and evenly distributed throughout 

 the year, and our big winds are mostly associated with rain. It is in 

 semiarid regions where long periods of drought may be followed by 

 torrential rains that soil erosion becomes an active danger. Still, I 

 have known cases: some 40 years ago in the Lincolnshire Wolds near 

 Louth an intense thunderstorm, such as is loosely called a cloudburst, 

 broke over a steep hillside on the chalk, the grass covering of which 

 had been broken near the top of the hill by a rabbit burrow. The 

 rushing rainwater got an entry there and in less than an hour had 

 stripped the hillside down to the bare chalk. I have known a similar 

 thunderstorm in Kent to remove 3 feet of soil from the hop garden, 

 leaving the plants with their network of roots suspended on the super- 

 structure of wire and string. I have again known a barley crop on the 

 Surrey sands blown into the hedge after it had become 2 or 3 inches 

 high. But these are rare instances, which serve only to illustrate the 

 risk of erosion in countries where our total rainfall of a year may be 

 concentrated into 1 day, or where scorching winds may obtain a run 

 of 1,000 miles over the steppe. 



The earliest cases of erosion to be noticed are those which follow 

 deforestation in regions where the mountains in which the rivers take 

 their rise are below the permanent snow line. In such countries, 

 typically in the eastern Mediterranean — Calabria, Greece, the greater 

 part of Asia Minor — the natural sequence is forest on the higher slopes 

 where the rainfall is greatest, passing into upland meadows as the 

 slope grows less and finally into river meadows as the river nears the 

 sea. There is no evidence in support of the belief that forests increase 

 the rainfall of a country, indeed, by the transpiration from their leaves 

 they must reduce the total amount of the rainfall retained by the soil, 

 but they serve as its regulator. The spongy soil below the trees, rich 

 in humus, absorbs the rain as it falls, whereby it reappears later in 

 the springs and furnishes the watercourses and rivers when the rainy 

 season has passed. But too commonly the forests have been cut down 

 without any regard to their regeneration; not only has the maximum 

 of timber been cut out but there has also been the desire to extend the 

 grazing. Grazing is all very well again if regulated, but unfortunately 

 in these Mediterranean countries goats are among the chief grazing 

 annuals. It is no accident that old tradition has represented the Evil 

 One with the hoofs of a goat, for of all animals the goat plays the 

 devil with land. Hungry goats will eat anything that grows; they 



