Human activities impact on soils in a variety of ways. One way that humans impact on soil is by reducing soil fertility and causing soil erosion.

Overcropping is an example of a human activity that reduces soil fertility. Overcropping has occurred in the Sahel region in Africa. The Sahel is a region south of the Sahara desert. Over-cropping in this region has caused desertification. This region has experienced rapid population growth in recent years. By the year 2000 the population of this region was 50 million. The demand for food put increased pressure on land. The natural vegetation of the region was cleared and farmers were encouraged to grow cash crops such as millet. The demand for food meant that farmers no longer used the fallow year to allow the soil to regenerate itself. Growing the same crop year after year (monoculture) removed nutrients from the soil, eventually rendering it infertile. The natural shrub vegetation of the Sahel provided protection for the soil. However once this natural vegetation was removed soil erosion increased. Topsoil was washed away by rainfall and the soil was also exposed to wind erosion. Vegetation helps to bind soil particles together and once this was removed the soil was exposed to wind erosion. The removal of vegetation also increased the effects of salinisation. The lack of vegetation resulted in an increase in evaporation and salts are drawn to the surface. This process renders the soil infertile and crops can no longer survive. The result is that desert conditions have spread into large areas of the Sahel.
 
Deforestation also reduces soil fertility. Deforestation is the removal of large areas of forest. Human activity is the main cause of deforestation.  Deforestation is occurring in many regions around the world, e.g. Amazon Basin in Brazil. In the Amazon rainforest the Brazilian government encouraged the habitation of the rainforest and cleared large areas of rainforest.  Once the rainforest vegetation is removed the soil is deprived of plant litter that provided nutrients in the form of humus for the soil. Nomadic farmers use the slash and burn method to clear areas of forest. The trees are burnt and the fertility of the soil is reduced.  The process of leaching increased as the soil was exposed to heavy, daily rainfall, further reducing soil fertility. The intense sunshine in this region burns the soil, turning it into a laterite meaning that it is no longer able to support any crops.

A second way that humans impact on soils is by damaging the structure of the soil. Soil structure refers to the shape of the soil peds. Soil peds are the small grains of soil. When the peds of soil are rounded it gives soil a crumby structure, which is the best structure for soil fertility. Overgrazing damages soil structure. Overgrazing occurs when large numbers of animals are allowed to graze in one area for too long. Evidence of overgrazing can be seen in Ireland. Mountains in the West of Ireland such as the Mweelrea mountains in Co. Mayo have been overgrazed by sheep over the last twenty years. Under the Common Agricultural Policy farmers were given grants for sheep farming in marginal areas.  Overgrazing by sheep meant the natural vegetation (mainly sphagnum moss) was removed. Animals such as sheep close crop the vegetation and it is unable to re-generate itself. Animals also trample the soil damaging the crumb structure of the soil peds, changing it to a platy structure and leading to soil compaction. This means that there is faster run-off of surface water and can result in localised landslides as there are no plant roots to bind the soil particles together.

Overgrazing also occurred on the slopes of the Appenines in Italy over the past few hundred years. Sheep and goats removed the vegetation from these slopes depriving the soil of nutrients. The soil was then exposed to heavy rainfall. All the productive top soil was washed away and deposited in rivers. This soil clogged the river channels and resulted in the formation of swamps and marshes.  

Overgrazing has led to soil erosion in the Sahel in Africa. Nomadic farmers allowed more animals to graze the land than it had the ability to support, removing the natural vegetation and eventually resulting in desertification. The situation was further worsened by the sinking of wells. Farmers sunk wells to provide water for animals; however, these wells used up groundwater further reducing soil fertility in the region. Population pressure meant that farmers were forced to farm the land more intensively and remained in the one area longer. Once the grazing animals removed the vegetation, the soil was exposed to the weather resulting in soil erosion and eventual desertification.