Peak Soil?

“When our soils are gone, we too, must go unless we find some way to feed on raw rock.” (Thomas C Chamberlin)

As a gardener I know that without caring for my soil, feeding it regularly with organic matter and green manure crops, my ability to produce nutritious vegetables will diminish over time. In his book Dirt: The Erosion of Civilisation, David R Montgomery, Professor of Earth and Space Sciences at the University of Washington, contends that the impact of massive and ongoing soil erosion on our own farming systems directly threatens the viability of our global society.


Our relentless use and overuse of that most precious of all our commodities the soil is summarised in a 1995 review of global soil erosion which reported the annual loss of twelve million hectares or arable land to soil erosion and land degradation (Pimentel et al, Science 267:pps 1117-23). And that doesn’t include the amount of land which is currently being lost to the expansion of our cities. Just look at the growth of Canberra’s suburbs or the suburbs of any of Australia’s capital cities and you can see what I mean.

Montgomery builds his case by looking back to the earliest periods of human agriculture and considers farming practices from Iceland to Ancient Rome, the Pacific Islands to modern day Cuba to examine the ways that human societies have farmed their soils. He also examines the impact on those societies when they failed to maintain the balance between soil erosion and the speed at which geological forces can replace this most precious commodity.

In the past people who exhausted their land could literally pick up and move on to new places, even new continents, but today with the ‘available’, not to mention usable land, shrinking rapidly this is no longer an option. But not every society overused or abused their soils. The Nile Valley has been under permanent cultivation for over 5,000 years and has remained productive all that time. However the changes wrought by the building of the Aswan High Dam and the associated move to commercial commodity production from smaller farms has had an extremely negative impact on soil fertility and soil loss since the mid-Twentieth Century.

For me it is his examination of the impact of agribusiness (or industrial agriculture) in the Twentieth century along with the impact of the use of artificial fertilisers, particularly since the World War II, that I find is the most interesting part of the book. I didn’t know that the artificial fertilisers which are the backbone of today’s agribusinesses were produced by the WWII explosives manufacturers who were just tooling around trying to see what they could do with their left over factory capacity after we stopped collectively blowing ourselves up.

Montgomery concludes that our own agricultural systems are close to collapse and if we do not start doing something about saving our soil fertility now – and no, loading more artificial fertilizers on to our farmland will not help. Montgomery outlines in the clearest possible way the grave danger we are facing:

The underlying problem is confoundingly simple: agricultural methods that lose soil faster than it is replaced destroys societies. Fortunately there are ways for very productive farms to operate without cashing in the soil, put simply we need to adapt what we do to where we do it….The cheapest input to agricultural systems, the soil will always be discounted – until it is too late.”

While tackling soil erosion is a complex problem there is still hope for our ability to maintain food production both at the small scale and broader agricultural level. The introduction of no-till planting for broad-acre crops has had an immediate impact of cutting soil erosion both in Australia and the US. For a dry continent like Australia soil conservation measures also double their benefits but helping drought-proof farms. One of the fastest ways to make new soil is by continuing to feed your own garden with composts, green manures and mulches.

In our own region Zerowaste Australia is implementing the Groundswell project to which is looking at the economic benefits of returning organic wastes from city rubbish tips back to agricultural land. So if you live in Queanbeyan your organic waste is currently being spread on paddocks in the Goulburn area. Local participants include farmers, the Wiradjuri Condobolin Aboriginal Corporation, the Palerang Agricultural Society, Bettergrow, Zero Waste Australia and the South East office of the DECC Sustainability Programs Division and the Goulburn Mulwaree, Palerang, Queanbeyan City and Lachlan Councils. You can follow their blog to keep up with what is happening.

Dirt is a fascinating read and my brief summary here doesn’t do the complexity of Montgomery’s case real justice – it’s far more subtle than I have managed to convey. I’d highly recommend Dirt to anyone with an interest in the ongoing maintenance and hopefully improvement of our society. So far this book isn’t in the ACT Public Library, but perhaps you can take advantage of the current exchange rates and the Christmas season to get a copy in from the US.

If you would like to hear David Montgomery talk about this fascinating subject you can check out an interview broadcast earlier this year on Bush Telegraph (ABC Radio National).