Farming is a form of natural resource extraction and when farmers neglect to steward their land depletion occurs and eventually they can no longer farm that land. But this risk seldom occurs unless there are economic and political pressures placed on farmers. Often the state demands a constant increase in agriculture outputs, which eventually has contrary results as outputs decline because of soil depletion.
For early Romans agricultural output slowly declined and population increased, per-capita energy availability dropped. The Romans solved this problem in the short term by conquering their neighbours to appropriate their energy surpluses (metals, grain, slaves, etc.). However, this solution merely exacerbated the issue over the long term; as the Empire grew, the cost of maintaining communications, garrisons, civil government, etc., increased. Eventually, this cost grew so great that any new challenges such as invasions and crop failures could not be solved by the acquisition of more territory. At that point, the Empire fragmented into smaller units.
We should remind ourselves that the coming apart of a society is not dramatic, it unravels very slowly and largely without notice, great civilizations have fallen because they failed to prevent the degradation of the soils on which they were founded. Our world today could suffer the same fate.
This is according to Professor Mary Scholes and Dr Bob Scholes who have published a paper in the journal, Science, which describes how the productivity of many lands has been dramatically reduced as a result of soil erosion, accumulation of salinity, and nutrient depletion.
"Cultivating soil continuously for too long destroys the bacteria which convert the organic matter into nutrients," says Mary Scholes, who is a Professor in the School of Animal, Plant and Environmental Sciences at Wits University.
Although improved technology -- including the unsustainably high use of fertilizers, irrigation, and ploughing -- provides a false sense of security, about 1% of global land area is degraded every year. In Africa, where much of the future growth in agriculture must take place, erosion has reduced yields by 8% and nutrient depletion is widespread.
"Soil fertility is both a biophysical property and a social property -- it is a social property because humankind depends heavily on it for food production," says Bob Scholes, who is a systems ecologist at the Council for Scientific and Industrial Research.
Soil fertility was a mystery to the ancients. Traditional farmers speak of soils becoming tired, sick, or cold; the solution was typically to move on until they recovered. By the mid-20th century, soils and plants could be routinely tested to diagnose deficiencies, and a global agrochemical industry set out to fix them. Soil came to be viewed as little more than an inert supportive matrix, to be flooded with a soup of nutrients.
This narrow approach led to an unprecedented increase in food production, but also contributed to global warming and the pollution of aquifers, rivers, lakes, and coastal ecosystems. Activities associated with agriculture are currently responsible for just under one third of greenhouse gas emissions; more than half of these originate from the soil.
Replacing the fertility-sustaining processes in the soil with a dependence on external inputs has also made the soil ecosystem, and humans, vulnerable to interruptions in the supply of those inputs, for instance due to price shocks.
However, according to Scholes, it is not possible to feed the current and future world population with a dogmatically "organic" approach to global agriculture. Given the large additional area it would require, such an approach would also not avert climate change, spare biodiversity, or purify the rivers.
However some people disagree.
Helen Browning is with the UK Soil Association and she wrote in “The Ecologist” that the need for farmers and growers to understand and protect soils has never been greater.
“We are destroying soils worldwide ten times faster than nature can restore them, and in the last 40 years, human activity has degraded 2 billion hectares of soil -over 15% of our land”, said Browning.
“As I converted my own farm, I always ensured that as a field started its move from chemical dependency to a biological, organic life, we helped it recover its vitality with some well-rotted manure. A few small applications are often better than one big one, as a ‘dead’ soil cannot digest manure and organic matter easily.”
Browning suggests that only 15% of land globally is suitable for growing food and even in the UK, where temperate climate reduces erosion risk, it’s estimated that 2 million tonnes of soil are lost each year, valued at £150 to £250 million. And across Europe, we 250ha / day is lost to development.
“How we put a value on this is not clear to me; our soils are invaluable. They store 10 times more carbon than the forests do; they are the fundamental resource on which human life depends. If we want to have more healthy people on the planet, then we need more healthy soil to sustain them.”
The above story is based on materials provided by Wits University.
Soil erosion is fast becoming one of the worlds greatest problems. It is estimated that "more than a thousand million tonnes of southern Africa's soil are eroded every year. Experts predict that crop yields will be halved within thirty to fifty years if erosion continues at present rates." Soil erosion is not unique to Africa but is occurring worldwide. The phenomenon is being called Peak Soil as present large scale factory farming techniques are jeopardizing humanity's ability to grow food in the present and in the future. Without efforts to improve soil management practices, the availability of arable soil will become increasingly problematic.
Some Soil Management techniques
3.Growing wind breaks to hold the soil
4.Incorporating organic matter back into fields
5.Stop using chemical fertilizers (which contain salt)
6.Protecting soil from water runoff
As the global population increases and demand for food increases, there is pressure on land resources. Land can also be considered a finite resource on Earth. Expansion of agricultural land has an impact on biodiversity and contributes to deforestation. The Food and Agriculture Organisation of the United Nations estimates that in coming decades, cropland will continue to be lost to industrial and urban development, along with reclamation of wetlands, and conversion of forest to cultivation, resulting in the loss of biodiversity and increased soil erosion