Matt Power, Editor-In-Chief of Green Builder Magazine writes in the March 2012 issue about how typical construction practices destroy soil ecosystems during development of new buildings. Stripping and mass grading, “attack(ing) a piece of land the way a three-year-old goes after a lump of Play-Doh”, typically divides the soil into one pile for topsoil, one pile for subsoil and one pile for sand. “Abused, misunderstood, poisoned and taken for granted, soils deserve better. They’re essential to life, more complex than you can imagine, and in serious need of stewardship”, Power writes. And soil ecosystems are very difficult to restore.
Power summarizes soil expert Mark Fulford’s message that “modern society- agriculture in particular- has gone astray.” Industrial agriculture following WW II is based on mining rather than biology, with the result that crops are “grown in a chemical soup” instead of in soils.
Typical construction site management reflects the same attitude toward the soil. Rip it up, pile it up, spread it out, compact it, re-spread soils and top it with turf treated with petroleum based nitrogen. Fulford calls that “carpeting a collapsed ecosystem.” His point is that there is no way to effectively restore the soils that natural processes produce in human terms at an extremely slow rate, at the rate of up to one inch per one thousand years. There is also no way to restore the amount of air in the soil that the roots need to thrive.
The best way to protect soil ecosystems is to disturb them as little as possible. A few key points taken from “Sustainable Landscape Construction” by J. William Thompson and Kim Sorvig with a few added comments include:
- Preserve and protect every tree (not usually feasible, so minimize removals)
- Use moveable, pervious pavers (or permeable paving)
- Minimize utility access damage (and think about what kind of backfill material makes sense)
- Plan staging carefully (minimize the limits of disturbance)
- Listen to the weeds. This refers to “Weeds and Why They Grow”, a classic 116 page guide by Jay McCaman published in 1994. By reading that, you get a free and quite accurate picture of the real qualities of the soil on a particular site. The idea is that observing which weeds grow where is a highly efficient way of identifying what the soils are lacking.
If soils have to be disturbed, the goals of restoration should include increasing carbon and air content. Fulford says that increasing soil organic carbon can “sequester enough carbon to get us back to the pre-industrial level…”
Our understanding of soil ecology has evolved but our typical construction practices have not.