Environmental Changes on the Southern Sides of Lake Chad (1951-1987)

Environmental Changes on the Southern Sides of Lake Chad (1951-1987)

Dynamic of evolutions of the southern sides of the Lake between 1951-1987
Carte n°4

As a consequence of climatic variations the Standard Chad phases are intersected with low lake levels. Three periods of little Chad have occured during the 20th century. The first lasted from 1904-1917, the second, around 1940, the third began in 1973 until 1997. At this date the lake Chad began to grow again.

We have realised a dynamic map based on two documents, one at the date of 1951 made by photo-interpretation by the National Geographic Institute of France, and the other based on the treatment of a Spot image taked in 1987.

We have done the implementation in a GIS of these documents (after interpretation based on vegetation thematic) to numerised them.

The superposition of the two periods indicated many new points :

After this long period of drought, different changes in the state of vegetation have been noted :

Species pertaining to trees and shrubs have strongly recolonized the shore in the areas where the level of the Lake’s waters have gone down and particularly between the dunes.
The aquatic vegetation which needs her higher water level has migrated to the north, thus spreading to the Lake’s free water.
As migrants suffering from famine due to difficult climatic and political situations are finding refuge around the Lake farming is spreading in the region.
As for damaged areas, they are located relatively further away from the Lake’s and the Chari flooding areas.

One of the main lessons to be learn from this period of changing climate is the absolute necessity of taking into account the ecological risks from rainfall variations.

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