exceeded hunters discover that they are having to travel further and further to find the animal and ultimately the animal may become extinct.
Extinction: the elimination of a species in a given area. For instance elephants are extinct on the Ogoni plain: elephants were recorded in the area up to the 1940s but they are no longer seen there.
As a more complex example of how ecosystems are damaged by our unsustainable exploitation of them, we can look at grazing in the Sahel in the far North of Nigeria.
Grazing in the Sahel: The ecozone south of the Sahara Desert is known as the Sahel. In its natural state it is a savannah ecozone characterised by annual grasses which are too scanty to carry regular fires, and by widely distributed trees, mainly of the Acacia genus. Rainfall is irregular but generally less than 600 mm a year. The boundary between the Sahel and the desert (where vegetation is limited to deep-rooted trees and shrubs, and a few drought-resistant perennial grasses) shifts according to rainfall patterns. These patterns vary over the years, decades and centuries, as a result of natural climatic cycles. Without any interference from man the Saheldesert boundary is not static: it will advance south during dry periods in the climatic cycle, and retreat north during wet periods.
From Viable Society's point of view the boundary between the desert and the Sahel savannah could be said to be the boundary between land which can be grazed and land which cannot be grazed. Old graziers will point out that this boundary oscillates over the years.
The grass in the Sahel savannah ecozone is a resource which Viable Society exploits very efficiently. In wet years when rainfall is plentiful and when the Sahara shifts north, the numbers of grazing animals increase. Their faeces improve the soil in terms of nutrients and structure (so much so that, traditionally, further south, Hausa arable farmers encourage Fulani owned cattle to graze upon the sorghum and maize stubble after the harvest). The high numbers of cattle ensure that grass and other vegetation is rapidly eaten so that a large proportion of the total biomass in the Sahel ecosystems is contained in domestic animals.
In dry years the Sahara moves south and grass becomes scarce: cattle have to be moved south or slaughtered for meat, otherwise they die of starvation. Usefully then, just as the Sahel ecosystems are being put under pressure by reduced rainfall, cattle grazing pressure is relieved. When the climate becomes wetter again, the Sahel ecosystems rapidly recover because they are not being grazed by large numbers of cattle, and the Sahara retreats north quickly.
In this example we can see how Viable Society is forced to accept ecological realities, and thereby is able to consistently exploit what resources the Sahel savannah ecosystems have to offer. The resource cycles, and ecological balance and stability are maintained, so that people's use of the ecosystem is sustainable.
However, given modern technology, Modern Society is able to maintain high cattle numbers in the Sahel longer during the dry period of the natural climatic cycle. This is usually achieved by sinking bore holes to mine water deposits that are part of a much longer resource cycle - water laid down during wetter geological periods. As a result vegetation is constantly grazed out and not given a chance to recover when the wet period of the climatic cycle comes around again. Therefore the desert perceptibly appears to move irrecoverably south, most dramatically seen as the sand dunes north of Gashua.
