by John Brouwer

“Behold this compost. Behold it well . . .
It grows such sweet things out of corruption.”

Walt Witman.

At the time of writing the city has again mobilized its army of 10 tonne trucks, huge vacuums, loaders, and staff throughout the neighbourhoods 3 times to battle a most insidious danger to urban life - leaves. A vast expenditure of dollars, energy, and greenhouse gases to interrupt a thoroughly natural process which over the millennia has created the topsoil on which life on earth depends.

No one collects the leaves in the forest. They just remain where they are and the natural organic processes gradually decompose them into the nutrients required to support life.

But our urban design has ignored natural processes so much that what is an essential element of natural recycling of life has been turned into urban warfare complete with a mechanized brigade to mop up the battlefield.

The forest decomposes organic matter and recycles it to provide the nutrients which support all life in the forest. This biological/chemical process is very complex but also very resilient so that it carries on through extreme climatic variations, catastrophic changes like fire and hurricanes, and even adapts itself to the chemical constituents of the underlying rock minerals. And, over time this process keeps building more organic topsoil to support more life in an ever-growing cycle. Human life would do well to imitate the forest.

However, we spend tens of millions to create a nano-technology center in the heart of the university, but these same universities do almost nothing to understand the complex biological interactions which support life on our planet. The understanding of the role of organic matter in soils came from the visionary J. Rodale who, on his own in the 1930’s, started working with organic matter in soils in rural Pennsylvania. Even today, no one understands the integracies of how a forest combines minerals with organic matter in recycling nutrients to make these available to support new life.

We could imitate the forest.

A first step is to utilize leaves where they are produced. All urban soils are deficient in organic topsoil so recycling organics in place will improves any urban soil.

Soil is an incredibly complex system of mineral matter, soil animals, fungi, and bacteria all working together in a symbiotic fashion to produce the food each needs and ultimately the nutrients which plants need to produces our food. Plants can not absorb organic matter directly. They need the fungi and bacteria to break up matter so that plant roots can absorb their nutrients.

It is believed that there are twice as many species of organisms living in the soil than there are in tropical rainforest canopies. Most soil animals (and microorganisms) occur in the top 5 cm of soil. The number of individual soil animals in the soil is enormous. In all but the driest environments there are billions of protozoa, millions of nematodes, and 100 000’s of mites in each square meter.

These soil organisms require air and moisture which is why soils need to be friable and loose so air can penetrate into the soil and moisture can be absorbed. These micro-organisms need to be encouraged and fed with organic matter so they in turn can produce the nutrients the plants need.

Mineral soils having no organic matter can only produce plants by the use of artificial fertilizers. Since most urban developers remove topsoil from the land as part of the development process, urban soils are deficient in organic matter.

But the immediate source of organic matter – leaves- are carted away by the municipalities! Some gardeners, recognizing the stupidity of this, manage to steal the leaves before the army arrives and decompose them for use in their gardens.

What to do?

Where they would not cover other plants, leaves can just be left where they are. By next summer most will have been decomposed by the soil animals.

A light covering of leaves on lawns where the grass has been trimmed to over 3”inches can just be broken up by using the lawnmower to cut up the leaves and the resulting pieces will settle among the grass blades down to soil level and encourage the worms in aerating the soil.

Where leaf accumulations are heavy, they can be raked (no one needs a gas-guzzling polluting leaf blower) and piled into an unobtrusive corner of the yard. A pile of leaves will decompose over several years. But the process can be accelerated by treating the pile as a compost pile. This just means that the entire pile has to be keep moist and aerated by turning the pile every few weeks. After a couple of months, the leaves will have decomposed to black compost which can be readily spread on lawns and gardens.

Over a hundred years ago Walt Whitman understood the marvel of decomposition creating new life. A little bit of similar education could go a long way today.