Despite what some may think, soil is not a renewable resource. We talk to experts about the importance of soil biodiversity and what growers need to consider.
Soil is not renewable. This has lately become the refrain of experts in the field. To fret over the roots of the planet is to be reminded that “There Is No Planet B”, as the writer Mike Berners-Lee put it, in the title of his defining book on carbon-footprinting. Some 95% of our food supply is grown in soil, more than 99% of our freshwater flows through it, and an estimated 25% of Earth’s creatures actually live in it, though most of them are microscopic.
Yet the rich, layered composition it may build up over millenia can be lost overnight to a single rainstorm. Those same experts tell us that least one-third of our soils have been degraded by combined effects of industrial agriculture, deforestation, pollution, and climate change. In areas like the Sahara, the damage is extensive, and a serious worry where most incomes depend on small-scale farming, while the local population is set to double by 2050.
More fertile-seeming regions, like the middle-American cornfields of Iowa, have also greatly deteriorated in terms of soil structure and organic content over the last half-century, without anyone really noticing until recently. “Many types of soil degradation are invisible,” according to Ronald Vargas, secretary of the global soil partnership at the UN’s Food and Agriculture Organization in Rome. “You just don’t see the loss of organic carbon from soils, or pollution building up in it, until you try to plant crops there.”
It’s not just a matter of C02 emissions affecting our capacity to grow food. “[Soils] are key for storing water,” says Vargas. “Good soil is like a sponge that soaks up the rain and keeps it there. It is important for recycling nutrients and storing carbon that would otherwise escape into the atmosphere.” This realisation has seen the growth of new initiatives to promote soil health around the world.
It’s a key strand of the One Acre Fund, which supports smallholder farmers in soil-protecting measures like agroforestry, intercropping, and composting across East Africa. Meanwhile, a major international research project called SOILGUARD is drawing on the work of 25 institutions in 17 countries to produce new evidence on the state of that biosphere and the likely impacts of human activity in coming decades.
Professor Paula Harrison of the participating team at the UK’s Centre for Ecology & Hydrology says the overall goal is “to raise awareness of raise awareness of the importance of soil biodiversity for the present and future wellbeing of humanity.” Unsustainable land management can have what Harrison calls “cascading effects on services provided by soils”.
The UK itself, often romanticised for its green pastoral landscapes, has seen those services disrupted by frequent flooding events in recent years. According to British soil health expert Professor Jenni Dungait, an entire winter crop can be lost after 15 days of waterlogging. This can be prevented, she says, by maintaining something close to an ideal soil structure, comprised of minerals like sand and clay, an even mix of air and water, and about 5% organic matter. So, farming practices have to change, as “heavy machinery and repeat cultivations are the main causes of soil compaction”.
Dungait has a list of imperatives for growers that may help improve the situation: “Limit farm traffic … use plants with large roots … try agroforestry, using fast-growing trees … ” And while modern agriculture has developed a bad reputation for its exploitative relationship with the land, some within the industry point out that farming also has massive potential for mitigating climate change. The edible plants we grow are oxygen-producing wonders after all, and crops can be “carbon-positive” if well-managed so that emissions are balanced against the carbon stored and captured by all those grains, stems, and roots.
As in other spheres, some combination of pre-industrial traditions and ultramodern tech innovations may yet help us turn things around. Professor Dungait has put it this way: “Our planet may be the only place in the universe where the conditions are right for soil to form. We rely on this miracle substance to grow our food, and it doesn’t usually let us down. So, most people, even some farmers, rarely think about the soil as more than ‘dirt’.”
In fact, she says, it’s the very essence of the Earth. The only way to solve our problems, and adapt to coming changes, “is to work in partnership with the life in our soils”.
