Soil is the Earth's skin, nourishing and supporting life: bacteria, natural vegetation, cultivated plants. Covering the soil is a thin coating of powder-fine minerals, or clay, that is rapidly degenerating and eroding. The Earth's soil, the fertile bedrock that made the human conquest of the planet possible, is being exhausted more rapidly than it can reconstitute itself. At the current rate of erosion, will it be capable of feeding the nine or ten billion human beings that are expected to inhabit the planet by the mid-twenty-first century?

This is the vital challenge posed here. Daniel Nahon begins by presenting the natural history of the earth's soils. He explains soil formation through the interaction of rock and water, and through chemical and biological reactions caused respectively by plants and bacteria. He shows that in geological times the Earth's surface was covered with a mosaic of ecosystems: arid deserts, hot and humid equatorial forests, icy tundra, temperate zones, etc. He then evaluates the impact of human activity on the soils.

This book is an appeal for the defence of the soil, i.e. for the defence of humankind.

Daniel Nahon, an eminent specialist on soil science whose works have won many international prizes, has written a fascinating adventure story about our planet. He describes the fascinating process that brought together rock and water, plants and bacteria to constitute Earth's fragile surface. He brings a forceful argument to the current discussions about the environment, and makes us face the vital challenge of feeding the planet. This is an indispensable work.

Daniel Nahon is a professor of soil sciences at Université Paul Cézanne, in Aix-en-Provence.