Soil covers most of the surface of the Earth’s land. It occurred after the erosion of rocks, due to strong winds, water, ice and due to the activity of living organisms. Soil is usually suitable for plants and small organisms to grow and live. However, human activities have altered the natural soil environment of many areas, making it hostile to organisms.

Humanity deposits many toxic substances under the ground. Most of those are radioactive materials, pesticides, heavy metals and other kind of poisonous wastes. Even if they are first deposited in lakes, rivers or the sea, waters transfer most of them in the soil, when the latter absorbs water. It happens the other way round as well, as chemicals within soil are transferred with the rain into marine ecosystems.

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There are many ecosystems on earth not rich in vegetation and other organisms. This is natural wherever there is low rainfall and hostile ground. However, there are other areas, in theory able to sustain a variety of living organisms, with enough rainfall and mild climate, but which have as little variety as the first category. Their soil remains poor and unsuitable for vegetation. Such ecosystems have been eroded by human activities, often to the point of desertification.

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There are many environmental problems caused by human but not widely known. One of them is eutrophication. This phenomenon cannot be entirely characterised as water pollution, as it mostly describes the process of too many plants growing in lakes, rivers and sometimes in the sea.

When household and industrial wastes are disposed into the water, they increase the quantity of germs in it. Germs threaten the health of the organisms living in the water, drinking it or feeding on organisms that live in it. Moreover, huge quantities of nitric and phosphoric salts enter the ecosystem. Phytoplankton, the tiniest sea organisms that can photosynthesize and depend highly on those salts, start to grow in population at top speed, consuming oxygen. As a result, zooplankton which feeds on phytoplankton starts to increase in numbers, again consuming oxygen and producing carbon dioxide.

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