SUBTROPIESE VRUGTE
We are not alone
– The soil, microbes and human health Ian Glass LOWVELD SUGARS
The good earth
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healthy, diverse microbe population in our environment and within each of us is essential for our own health and future survival. In 1937 Franklin D Roosevelt, President of the United States of America during some of its darkest days of a crippling economic depression coupled with soil degradation that led to the “Dust Bowl” phenomenon, wrote that “The nation that destroys its soil destroys itself.” These words were a stark reminder that the literal fabric of society and our very existence on this planet is facilitated by the ability of our soils to produce food for our survival. With advancements in scientific observation and understanding, more and more investigation is underway into examining the correlation between the health of these life-giving soils and our own health and well-being. The connection between soil and human health has long been recognised, if not well understood. In 500BC, Hippocrates of Cos, the father of modern medicine, wrote: “When a physician comes to a district previously unknown to him, he should consider ... the soil; whether it be bare and waterless or thickly covered with vegetation and well watered; whether in a hollow and stifling, or exposed and cold.” Likewise, we have recorded in the book of Numbers, chapter 13: “When Moses sent them to explore Canaan, he said, ‘See what the land is like and whether the people who live there are strong or weak, few or many. What kind of land do they live in? Is it good or bad? How is the soil? Is it fertile or poor? Are there trees in it or not? Do your best to bring back some of the fruit of the land.’” Ninety-five percent of all life on earth lives in the soil, however as Leonardo Da Vinci observed: “We know more about the
GROENTE & VRUGTE | NOVEMBER • DESEMBER 2021
movement of celestial bodies than about the soil underfoot.” The concept of “the good earth” has long been part of the human psyche. Given that almost all of the calories that humans consume come from food produced via the soil, the symbiotic relationship between fertile soil and human life is profound. However, as science began discovering microbes, their presence in the soil and the link of some (like tetanus) to human disease and infection helped create an attitude that the soil is a dangerous place and that things in the soil are trying to kill us. This has influenced our attitudes as to how we treat this invaluable resource. It is estimated that approximately 10 million hectares are lost annually to erosion or increased salinity, while another 20 million hectares are abandoned annually due to decrease in fertility levels. Our overuse of tillage, pesticides and fertiliser has had a huge impact on the microbial and fungal life of soil. Dead soil is more prone to erosion and water logging. Water logged soils in turn are more hospitable to anaerobic bacteria, many of which are plant pathogens. The depletion of microbes that are able to scavenge and hold nutrients has led to the need for higher artificial fertiliser inputs and greater environmental pollution. Nitrate run-off contaminating water resources, residual chemical pollutants taken up by crops leads to human and animal consumption of toxins. Toxins include heavy metals like lead and arsenic. Both of these occur naturally in the environment, but the effects of microbes and other minerals in healthy soils form bonds that render them less or non-toxic. Nitrification from excess fertiliser, however, leaches lead out of these bonds. Arsenic is a component of common herbicides and is a contributor to many cancers and other diseases. These and other pollutants can cause a large array of health issues. The concentrations do not need to be high in the soil but the accumulative effects can lead to toxic levels in animals and humans. TO PAGE 16
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