| Summary: | If the importance of soil for human lives hasn’t leapt out of the previous pages, this book has failed in its goal. Soil touches so many aspects of human life, often in ways of which we are not even aware. There are the obvious, such as when we dig up the soil to grow vegetables and flowers, or when a farmer takes a plough to a field. But there are also the less obvious, such as the role of soil in dampening climate change, filtering the water we drink, and breaking down and recycling the billions of tonnes of dead plant remains that annually fall to the ground. Soils have also played their role in warfare, thwarting military advances and providing underground shelter to those under attack. I could go on, but I think the message is clear: earth matters. Looking to the future, a major challenge for humans will be how to deal with rapid soil change. I emphasized at the start of this book that the natural rate of soil formation is spectacularly slow; it takes literally thousands of years for a mature soil to develop. But within just a few years, or decades, humans can completely transform the structure, chemistry, and biology of soils, often leading to their degradation. This degradation of soil can be catastrophic, for example when soils are over-cultivated or overgrazed, or when unstable hill slopes are deforested and left exposed to the erosive forces of wind and rain. Or it can be progressive, such as that caused by climate warming which, in some places, such as the Arctic, is gradually speeding up organic-matter decay and carbon dioxide release from soils. It can also be abrupt, such as when land is sealed by asphalt and concrete during the construction of expanding cities, or during war when major offensives obliterate the fabric of soil. As I stressed earlier in this book, the causes of soil degradation are complex: population growth, poverty, poor delivery of information to farmers, conflict, shortage of land, and climate change all play a role.
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