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Urban Soil Creates Unexpectedly Fertile Mosaic

When I was six, my mom found me sitting at the edge of our suburban home, where I was grabbing fistfuls of soil, and eating it. She washed my face and warned me that soil could be dirty; there were very bad things in it that could make you sick. But it turns out that urban soil may not be as disturbing as we might expect. Even with so much human use and waste filtering through it on a daily basis, urban soils might have more fertility and variety than we think.

According to the current issue of Baltimore Ecosystem Study, found that while some soil was obviously disturbed by the urban environment, such as through construction or deconstruction, other soil had characteristics of soil that would be found outside the city limits. While the physical characteristics of samples were similar, the chemical make-up varied depending on the history of use, location of the site, and any buildings, asphalt, turf or concrete that may have covered the site at one time. Calcium rich concrete for instance may have elevated the calcium levels in the soil, making it more alkaline. Such levels are important to understand because they can impede plant growth.

But to their surprise, the researchers found that elevated levels of heavy metals in the soil appeared to be related to geology rather than the city’s history of industrialization.

Even so, the researchers plan to continue testing the relationship between heavy metals and urban soil. But it is possible that time, and more carefully use, even in the short span of a couple of decades, have already started to heal the industrial wounds of the urban landscape where a single teaspoon of healthy soil can be home to a billion bacteria, yards of fungal filament and handfuls of nematodes.

The researchers expect that similar results would bear out in other regions since they were evaluated based on human uses that are common in urban landscapes.

But in areas of the West, where mining and logging were prevalent, similar soil tests have revealed very different results, particularly on the many superfund and brownfield sites in our region. (A brownfields is land defined by the Environmental Protection Agency as abandoned or idle with real or perceived pollution.)

How far these pollutants have traveled in the soil remains in question without testing the surrounding area and mapping the urban west’s soil mosaic. Until then, our Rocky Mountain urban soil is probably not something you want a 6-year-old to eat.

For more information on soils, visit
The American Society of Agronomy
Crop Science Society of America
Soil Science Society of America

The author is the Brownfields Coordinator for the City of Missoula.

If you have any questions about this program, contact your EPA regional officer.

Each week in the NewWest.Net “Spade & Spoon” section, writer Kisha Lewellyn Schlegel discusses the localization of the food system in the Rocky Mountain West by profiling organizations and individuals who are attending to the issues and possibilities of eating closer to home. Bookmark Spade & Spoon at www.newwest.net/spadeandspoon.

About Kisha Lewellyn Schlegel

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One comment

  1. Very interesting…somtheing to think about…well written!