Soil quality essential to Earth's inhabitants

It has been noted that human survival on this planet relies primarily on sun, rain and a thin layer of topsoil.

The sun is pretty consistent, rain can be unpredictable but the topsoil we too often treat as mere dirt, ignoring that it is the part of the equation that actually provides the nutrients that are facilitated by the other two.

Conventional systems of growing have treated the soil as just a growing medium to which we add artificial nutrients in the form of fertilizers. To a degree this has worked, as super phosphate and urea have improved crop growth, but at the expense of the micronutrients that a healthy soil provides.

For example, a cup of undisturbed natural soil may contain:

•Bacteria 200 billion

•Protozoa 20 million

•Fungi 100,000

•Nematodes 100,000

•Arthropods 50,000

All of these go to make soil minerals and organic matter available and also better retained in soil, instead of washing out as happens to many artificial fertilizers.

A soil's natural biota can be disrupted, particularly by over cultivation, herbicides and pesticides.

Then, after we have produced food from all this effort, about half of it is waste from food preparation and left overs, destined to landfill where its nutrients are certainly wasted.

There has been some discussion lately about species extinction and how fast it is happening, or even if it matters.

An estimated 99 per cent of all species that have ever existed are now extinct.

So it is no surprise that species are still going extinct, and the fossil record suggests that for most of the planet's 3.5 billion year history the steady rate of loss of species is thought to be one in every million species each year. Except that now the International Union for the Conservation of Nature (IUCN) calculated in 2004 that the rate of loss had risen to 100 1000 per million annually, comparable to the previous mass extinctions like the dinosaur's extinction.

But the rate of new species evolving is much slower than those going extinct.

Which is why the biota of the soil is important. It is time we reversed the damage we have been doing to soil and it is something we can readily do.

It is quite simple, really, to return that which originated in the soil back to the soil, completing the circle. Individually if you can have a compost, set one up, if you are not able to, your garden waste can be recycled locally via the transfer stations (and soon the Resource recovery centre) so it can be composted locally.

There is often little appreciation of the variety of life that our existence relies on. From viruses to whales, the loss of any one of them could potentially be the trigger that could create a domino effect of extinctions, changing our planet irrevocably.

John Milnes is a founder and trustee of Sustainable Whanganui and was the Green party candidate for the last three elections. He began his working life at the Department of Scientific and Industrial Research.