Because we walk on the ground every day, we forget that soil is both essential and fragile. Plants, for example, draw the nutrients they need from the soil to produce living matter-and oxygen-through photosynthesis. The ground is also the base for almost all human activity, including housing, farming and transportation. Lastly, all of the water that feeds underground aquifers filters through the soil.

Soil is fragile because it depends on the active balance between its creation, from alteration to the parent rock, and its destruction through erosion. It is also subjected to the consequences of human activity, including industrial pollution, farm waste, nutrient depletion, compacting, desertification following deforestation, etc.

While soil is just as essential and fragile as air and water, it is less well understood and protected. Soil and subsoil are complex; composition can vary widely even in a single location, organic and chemical activity is often intense and water can circulate in different layers.
Because soil is not transparent, our knowledge is often imprecise. It can be very difficult, for example, to accurately map the extent of soil pollution and its movement and determine the type of contaminants and their concentration.