It’s a strange notion, but some experts fear the world, at its current pace of consumption, is running out of useable topsoil. University of Sydney professor John Crawford talks on the seismic implications soil erosion and degradation may have in the decades to come.
Is soil really in danger of running out?
A rough calculation of current rates of soil degradation suggests we have about 60 years oftopsoil left. Some 40% of soil used for agriculture around the world is classed as either degraded or seriously degraded – the latter means that 70% of the topsoil, the layer allowing plants to grow, is gone. Because of various farming methods that strip the soil of carbon and make it less robust as well as weaker in nutrients, soil is being lost at between 10 and 40 times the rate at which it can be naturally replenished. Even the well-maintained farming land in Europe is being lost at unsustainable rates.
Why haven’t we heard more about this?
Probably because soil isn’t sexy. People don’t always think about how it’s connected with so many other things: health, the environment, security, climate, water. For example, agriculture accounts for 70% of our fresh water use: we pour most of our water straight onto the ground. If soil is not fit for purpose, that water will be wasted, because it washes right through degraded soil and past the root system. Given the enormous potential for conflict over water in the next 20- 30 years, you don’t want to exacerbate things by continuing to damage the soil, which is exactly what’s happening now.
How does soil erosion happen?
Soil is a living material: if you hold a handful of soil, there will be more microorganisms in there than the number of people who have ever lived on the planet. These microbes recycle organic material, which underpins the cycle of life on earth, and also engineer the soil on a tiny level to make it more resilient and better at holding onto water. Microbes need carbon for food, but carbon is being lost from the soil in a number of ways. Simply put, we take too much from the soil and don’t put enough back.
Firstly the classic approach was to leave stubble in the field after harvest. This is now often being burnt off, which can make it easier to grow the next crop, or it’s being removed and used for animal feed.
Secondly, carbon is lost by too much disturbance of the soil by over-ploughing and by the misuse of certain fertilizers.
And thirdly is the problem of overgrazing. If there are too many animals they eat all the plant growth, and one of the most important ways of getting carbon into the soil is through
What happens if this isn’t addressed?
There are two key issues. One is the loss of soil productivity. Second, water will reach a crisis point.
To be continued