PHYSICAL GEOGRAPHY 
37 
Africa one is constantly encountering marshes which even in native tradition (to 
say nothing of the geographical evidence) were once large lakes. Again, there 
are fertile depressions which are no longer marshes. Dry stream valleys mark 
the courses of once powerful torrents. This tendency towards decreased 
rainfall is undoubtedly due, in my opinion, to the action of man. It is scarcely 
exaggeration to say that had British Central Africa been left for another couple 
of hundred years simply and solely to the black man and the black man had 
continued to exist without thought for the future as he does at present, this 
country would have become treeless, as many portions of it were becoming 
when we embarked on its administration. Livingstone describes in his Last 
Journals the process that is going on in Manyema, to the west of Tanganyika, a 
country once covered with the densest forest. The natives make clearings for 
NATIVE CLEARING IN FOREST COUNTRY 
their plantations. They cut down the trees, leave them to dry and then set fire 
to them and sow their crops amongst the fertilising ashes. The same type of 
forest never grows up again. It is replaced by grass or by a growth of scrubby 
trees—trees of a kind which can to a greater extent resist the annual scorching 
of die bush fires. Besides this wanton destruction of forest for the growing of 
food crops (and as a rule the native merely grows one crop of corn and then 
moves off to another patch of virgin soil, leaving the old plantation to be 
covered with grass and weeds) the annual bush fires play a considerable and (if 
unchecked) an increasing part in the disforesting of the country. Even where 
large continuous areas of dense forest remain, so evergreen and full of sap as 
not to burn easily, each year the raging fire will sere and dry and kill those trees 
which are on the forest outskirts. The next year these dead trees are consumed 
by the fire which again dries up and kills another rank ; so year by year the 
forest diminishes in area to extinction, unless protected by happening to grow in 
