One-third of Earth’s soil is degraded because of unsustainable farming methods, which could lead to a major food crisis.

Late last year, the United Nations’ Food and Agriculture Organisation (FAO) released a hair-raising report on the state of the world’s soil and water resources. The bottomline: 25 per cent of the world’s food-producing soils are highly degraded or are rapidly being degraded. Add to that other soils which they say are degrading “moderately”, and the area under threat amounts to one-third of the Earth’s endowment of cropland.

Loss of productive soil, FAO reported, is most severe in the Himalayan and Andean regions; semi-arid tropical regions of Africa and India; rice-growing lands of Southeast Asia and areas of intensive and industrialised farming in Western Europe, North America, eastern China, India, Brazil and New Zealand.

We humans now grow two-and-a-half to three times as much food as we did in 1960 while cultivating only 12 per cent more land area. It’s an extraordinary achievement, but the cost has been high. Tilling, fertilising and irrigating year after year damages the soil’s native structure, and the water that runs off into streams or percolates into groundwater can be laced with dangerous quantities of nitrates, pesticides or other pollutants.

The fate of the Earth’s agricultural lands is closely tied to the fate of its waters. Expansion of irrigation has been the biggest factor in increasing food production over the past half-century, and improving irrigation will be a key to boosting yields between now and 2050. But irrigation can deplete local water resources and disrupt the soil’s chemical balance. Furthermore, flooding of reservoirs has already driven tens of millions of people off of perfectly good forest and cropland around the world.  

Back to traditional methods

While declining soil health is a global problem, many of the soils in critical condition are in the global South. Tropical soils are especially vulnerable, and when they’re farmed, all kinds of problems can be expected: loss of essential nitrogen, phosphorus, potassium and micronutrients; washing away of already-thin topsoil; carbon depletion; crippling of the soil’s ability to store water; buildup of salts and aluminum toxicity; acidification and perhaps most importantly, destruction of the many species of microorganisms needed for a robust soil ecosystem.

When that has happened, farmers have still managed to produce harvests by pouring on synthetic fertilisers (if they can afford them.) Instead of restoring the soil, that renders it a more-or-less inert growth medium.   

The cost of producing sufficient food between now and 2050, while retaining soil’s productive capacity on the global scale, was estimated by FAO at US $1tn for irrigation improvements plus $160bn for soil conservation. Governments of the global North could easily pay for that; such sums are not huge at all when viewed alongside the North’s expenditures on, say, armaments or corporate bailouts. But the cheque’s decidedly not in the mail. 

And many farmers are not waiting to see that cheque before pushing back against erosion and loss of fertility. Using resources at hand, they’ve built terraces; planted rows of trees and shrubs; built water-breaks with crop residues or brush; interplanted nitrogen-fixing legume crops with cereals, root crops or perennial forage grasses; returned manure or nitrogen-rich leaves and stems to the soil and built field-scale rainwater-harvesting systems. 

Researchers who’ve been working for years to improve food production on tropical soils say it will take more than cash to reverse the damage, and that what farm communities lack in the form of money and labour power they can make up for with “social capital” - their capacity to act collectively to protect their common life-support system, the soil.      
 
Given sufficient social capital, communities have taken on even more ambitious soil-conserving projects that bring long-lived, deep-rooted trees and shrubs into agricultural plots - a group of techniques known as agroforestry. Examples can be seen on every continent.

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