HUMAN GEOGRAPHY


16 Human Interference with Soils


Soil is a renewable resource that can be used again and again provided it is managed properly. But soil usually depends on vegetation cover for its fertility and its survival. People sometimes destroy vegetation cover by deforestation,* by overgrazing* or by overcultivation.* The soil then loses its fertility and may become exposed to and destroyed by agents of erosion such as running water and wind.


Case Study 1: Deforestation in the Amazonian rainforests


Venezuela Manaus B r a z i l Bolivia


Amazonian rainforests


Size of Ireland compared to rainforest


State of Rondonia 0 500 km Tropic of Capricorn Equator


The Amazonian rainforest is a vast region of hot, wet equatorial climate (see Figure 1). Daily temperatures there average a high 28ºC throughout the year and afternoons are typically marked by heavy convectional rain.*


Selva is the name given to the vast, dense rainforest


that forms the natural vegetation of the Amazon Basin. These equatorial rainforests are among the most luxuriant and biodiverse* in the world. They contain a vast array of plant and animal species. Yet the soils of the equatorial rainforests – which are


1 186 The Amazonian rainforest and its size in relation to Ireland


called tropical red soils or latosols – are not naturally fertile. They maintain their fertility only through a delicately balanced relationship between equatorial climate, forest and soil (see Figure 2). They depend largely on the forest for their fertility. For many centuries, the only human inhabitants of the rainforests were small numbers of Amerindian*


people. These people did little to upset the delicate balance of the selva’s ecosystems* or the fertility of its soil. Since the 1960s, however, the region has endured an ever-growing influx of people from outside the rainforest who are determined to clear the forests for short-term profit.


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