Tropical Forests 
kind is a very difficult undertaking. But when once a 
strip of such jungle has been cut and burnt off, it will, 
after a few years under crops, be allowed to relapse into 
bush, Secondary forest will spring up which is by no 
means so dense or so difficult to clear away as the 
original jungle. Possibly after some seven years in 
bush it will again be brought under crops. All this 
clearance and destruction of the wet-jungle enormously 
improves the climate, especially from a white man’s 
point of view. 
‘In Southern Nigeria, according to an interesting report 
just published,’ a strip of forest 1000 yards wide along 
both banks of the river has been by law reserved, so that 
the wet-jungle seems already to require protection by 
the British Government. 
This same report also contains an excellent account 
of the way in which in “dry zones” the natural wood- 
lands tend to be replaced by grass (see above, p. 268). 
Where the rainfall is less than 50 inches, the natural 
bush cannot hold its own against fires. Some young 
trees are destroyed and others injured. Grasses are not 
killed by these fires, but all valuable dead leaves and 
other good material is burnt up, and in consequence 
the land deteriorates steadily. So that there really is 
some hope that the wet-jungles of Africa and South 
America will no longer bid defiance to civilised man. 
In Bombay, in those early days when Europeans first 
established a factory, the mortality was terrible, and quite 
as bad as it used to be in Old Calabar from 1880 to 
1890, and this fact is of course quite encouraging for 
Old Calabar. Mangrove swamps are quite distinct and 
different from the ordinary wet-jungle. 
The estuaries of tropical rivers are often of enormous 
extent, for any large stream is apt to split and divide 
itself into a complex series of winding creeks, a vast 
confused delta, where the air is for ever hot, moist, 
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