The soil is the great connector of our lives, the source and destination of all.—Wendell Berry

Next time you rinse the dirt from your carrots, give a moment to think about the stuff that goes down the drain.

Most of us don’t pay much attention to soil. We may have a basic understanding that soil is useful for growing plants, but the significance and fragility of this “great connector” gets lost on us—until it’s gone. And once it has disappeared, natural processes can take a good 500 years to build up one inch of topsoil.

By our very existence, humans deplete soil. Salinization, desertification, erosion, and chemical contamination are just a few of the myriad ways. In Collapse: How Societies Choose To Fail or Succeed, Jared Diamond illustrates how civilizations as diverse as those once found on Easter Island, in Norse Greenland, and in the ancient Mayan city of Copan (now Eastern Honduras), collapsed, at least in part due to soil mismanagement. Easter Islanders and the people of Copan depleted their soil through deforestation, while the Greenland Norse dug up turf to build houses (and churches). And here in the Fraser Valley we’ve paved over some of the richest agricultural soil in the world to build highways, strip malls, and big box stores.

The Copan deforestation caused hillsides to be leached of nutrients and to erode. Diamond speculates that these infertile soils swept down into the valley bottoms, where they eventually buried the more fertile lowland soil, reducing agricultural yields. A similar situation threatens land closer to home, explains UBC soil scientist Art Bomke. Developers building on hillsides often don’t consider the impermeable surfaces that are created through road and housing construction—and when it rains, topsoil gets washed down into the valley bottom.

To forget how to dig the earth and tend the soil is to forget ourselves.—Gandhi

Farmers realize that the real goal is to grow and strengthen their soil. Along the way, they grow food for themselves and for the rest of us eaters. The by-products of their labour (manure and composted plant material) create a robust and resilient section of earth. But even with well-managed soil, farming by its very nature depletes the soil. One reason for supporting and sustaining local agriculture is to harness the nutrients in our own soil. “You have boatloads of grain going out of Vancouver to China, Korea, Taiwan, and so on,” Bomke says. “We’re exporting nutrients, especially nitrogen and phosphorus.” And nitrogen and phosphorus are two of the big three components, along with potassium, in chemical fertilizers.

All terrestrial food comes from the soil; it partners with sunlight and water to supply everything a crop needs to grow. Even the animals and animal products that we consume feed on plants that grow in soil. But these simple, universally understood facts are underscored by an equally simple fact: we are losing soil. A 2006 report by Cornell University concludes that soil is being lost at a rate 10 to 40 times faster than it can be replenished worldwide.

So, how can an urban dweller help build healthy soil? Bomke suggests big picture solutions like system redesigns to capture all of the nutrients and organic matter that flow into our cities. “We really have to look at recycling and reusing our organic wastes effectively.”

If you’re lucky enough to have access to native soil in your backyard or community garden, Bomke has some advice for strengthening what you’ve got. First off, keep the soil beds permeable. “Keeping them open, so that they accept and drain water off at a reasonable rate, keeps water in the city so you don’t have to irrigate so much. It means less run-off, less stress on the storm drains, and it usually goes along with good plant production as well.”

Secondly, he suggests retaining the organic matter available to you. If you live on a street with trees, the autumn leaf fall is great for mulching and adding to your compost pile. “I don’t purchase compost from anywhere else; I’ve got enough right there.”

Every time we eat, we owe a nod of gratitude to the soil for supplying us with the nutrients that keep us alive. Last year it was widely reported that poor Haitians were resorting to eating “cookies” made of salt, vegetable shortening, and dirt—and that was before the earthquake. A dirt cookie is the last resort of desperate people intuitively understanding that they need to get nutrients into their famished bodies any way possible.

And while we in Metro Vancouver aren’t close to such desperate measures, we will inevitably reach peak soil. One study estimates that 38,000 square kilometres of this planet are turned into desert every year. We’ve lost five billion acres of arable land since the first wheat and barley crops were planted 10,000 years ago, and in the past 40 years, 30 per cent of Earth’s arable land has become unproductive. We are blessed to live in a physical environment that simply hasn’t been exploited long enough by human activity to be seriously degraded. But if we don’t learn to protect what lies beneath our feet, all our talk about local food will be moot as we munch on dirt cookies.

Jeff Nield works with FarmFolk/CityFolk Society where he encourages people to think about where their food comes from, how it’s produced and how it gets to them.