One hectare of soil contains 15 tonnes of organisms—equivalent to the weight of 20 cows.
Directly under our feet is a living ecosystem that supports us and provides us and our planet with the nourishment that sustains us. The soil. It performs innumerable services for humans, animals, and the environment. The soil layer regulates and stores nutrients and water. It is thanks to the soil that we have clean drinking water; soil also forms the basis for the production of more than 95 per cent of our food supply.
The soil constitutes the second-largest carbon reservoir on the planet (surpassed only by the oceans); it plays a major role in regulating the global climate. But this is only possible with the help of billions of tiny assistants who make their homes in the soil. Taken together, the organisms in a hectare of land weigh as much as 20 cows: they include microorganisms, bacteria, spiders, beetles, and worms. Creatures that cause many of us to shudder when we see them thus in fact perform many functions that are crucial to ensuring our survival. Soil also plays a decisive role in preserving biodiversity.
Together, tiny creatures, plant roots, and humus make up about 7 per cent of the soil; the remainder consists of some 45 per cent mineral particles such as sand and clay, 25 per cent air, and 23 per cent water. Adequate air circulation and water supply are important to maintain the structure of the soil, to assist the activities of the soil-dwelling organisms, and ensure that the plant roots have sufficient access to oxygen. But the organisms in the soil are not the only ones who depend on it; directly or indirectly, many people also earn their livelihood from the soil.
If we are to achieve the goal of worldwide sustainable development, how we take care of the soil will be essential. We cannot afford to destroy the living surface of our planet by exhausting its capacity, burying it under asphalt, or allowing it to erode away.
Photo credit: Soil Atlas 2015 (http://globalsoilweek.org/soilatlas-2015)