REBOISEMENT IN 
MOUNTAIN AREAS 
As used in this letter the term ‘‘reboise- 
ment” includes both the actual replacement 
of forest on the mountain slopes, naturally or 
artificially, and also the other work that has 
been carried on in connection with the re- 
forestation. The development of reboise- 
ment has been the joint work of engineers 
and of foresters. But taken as a whole there 
is no question that reboisement activities are 
properly to be classed under the head of for- 
estry. 
It was stern necessity that forced France 
to undertake the reboisement of her high 
mountains. For practically a century the 
work of rectifying the errors of earlier days 
has been going on, and the job is not com- 
pleted even yet. Approached from whatever 
standpoint the work that France has done in 
the French Alps constitutes one of the most 
interesting chapters in the whole history of 
forestry. It is a chapter full of significance 
to all other countries. 
As will be recalled, France has the advan- 
VALLEY ABOVE CHAMONIX SHOWING 
LONG LINES OF BARRIERS TO PRE- 
VENT THE START OF AVALANCHES 
tage of having high mountain ranges along 
much of her frontier; notably the Pyrenees 
on the southwest and the Alps on the south- 
east. But with the advantages come also 
drawbacks, one of which is the damage liable 
to result from the mountain streams where 
man has interfered with the vegetation that 
naturally covers their catchment areas. The 
control of torrents becomes therefore the 
keynote of forest management in the high 
mountain regions, for as an eminent French 
forester, Jacquot, has aptly said, ‘‘The forest 
is the sovereign regulator of water flow. Its 
presence stops the formation of torrents. Its 
development extinguishes it. Its destruction 
delivers the soil as a prey to erosion. All the 
fundamental laws recognize the absolute ne- 
cessity of reforestation’’. This is a transla- 
tion from ‘‘LaForet’’, by A. Jacquot, as given 
in appendix B of “Studies in French Fores- 
try’, T. S. Woolsey, Jr.; John Wiley & Sons, 
N. Y., 1920. This book, as noted in an ear- 
lier letter in this series, is now the standard 
authority in English on forestry in France. 
The statistics given in this letter are mainly 
taken therefrom. 
The discussion of the damage resulting 
from torrents may perhaps be facilitated by 
the following definition, also taken from 
Major Woolsey’s book, just cited (P. 150): 
“A torrent gorge is a temporary or perma- 
nent water course in which the water con- 
centrates with extreme rapidity after heavy 
rains and by its energy of movement digs out 
its bed, which is considerable because of the 
mountain slope and because of the increase 
in density of the material transported. The 
soil and debris of all kinds eroded by the wa- 
ters are deposited on the plain’. The slope 
of torrents may exceed six percent for their 
entire course. It is never less than two per- 
cent. 
Two thirds of the torrents of Europe are 
said to be in France; the remainder being in 
Switzerland and Italy. The damage that they 
cause is not limited to the direct erosion and 
the destruction that results from the deposit 
of debris on near-by agricultural lands. The 
effect of uncontrolled torrential streams 
makes itself felt all the way to the sea. It 
is this phase of the question, quite as much 
as the local damage, that gives to the prob- 
oe of torrent control the importance that 
i as. 
THE HISTORY 
OF REBOISEMENT 
The necessity of keeping a forest cover on 
the mountain slopes were early recognized in 
France. It was advocated by Bernard Pa- 
lissy in the sixteenth century. And indeed 
his work paved the way for his successors 
Im recent times. But as so often seems to 
be necessary where man is dealing with the 
forces of nature, it took a series of catastro- 
phes to arouse the people of France to the 
absolute need of systematic action. 
(54) 
