us will have encountered before – but we are probably very well aware of its devastating effects on our land. As the term suggests, over-cultivation is the excessive use of farmland to the point where productivity falls due to soil exhaustion or land degradation1.
Over-cultivation which leads to land degradation is a problem that stretches to about 30 % of the total global land area. It is also a problem that persists, with a reported loss rate of about 10 million hectares per year. What is more, as agricultural land becomes degraded, land managers move to other pieces of land which means that we are degrading the productive land we have left and abandoning large chunks of land that we have left unusable2.
Why does over-cultivation happen?
Over the last 5 decades, increases in agricultural productivity have made it possible to produce more crops on the same amount of land. And that helped tremendously secure food for an increasing population. It is important to remember that at the time many regions of the world were recovering from years of war, particularly in Europe. So, access to food was a priority for governments as they were rebuilding their nations.
Unfortunately, however, today’s intensive farming techniques have come to require ever increasing inputs of resources such as fertilisers and pesticides to yield ever increasing produce. The problem with this is that this is not a linear relationship. In other words, there comes a time when no matter how much resources and capital is poured into the land in the form of water or fertiliser, it will not yield more crops; indeed, the opposite may happen. This when the point of over-cultivation has been reached.
Negative impacts of over-cultivation
We now know that over-cultivation is an unsustainable use of land and in extreme circumstances, it can lead to permanent damage to the productivity of the land to the point of desertification. Desertification is a real risk as over-cultivation creates a number of problems.
First, it has a very negative impact on the soil as over-cultivation can lead to both soil degradation and erosion. As natural vegetation of a specific area is cleared to make space for farming and then when the farmland is ploughed, the topsoil can be blown away by wind or washed away by rain.
Data regarding the amount of soil we lose is truly staggering: in Brazil, soy production causes the loss of 55 million tons of topsoil every year 2.
Top soil is particularly important as humus, the fertile layer of soil is normally found near the surface. The size and quality of the humus layer can be reduced quickly once native vegetation is cleared out and the land begins being farmed. With over-cultivation, which minimises the space that the land is not ploughed, soil fertility is further degraded as there is no time to replenish nutrients3. Soil degradation and loss leads to reduced soil fertility and degraded land.
What is particularly concerning is that over-cultivation is not just an issue of the profitability of agricultural activities. Falling yields put food security at risk and very often, in poorer countries, it can lead to internal conflicts among people fighting over scarce resources.
For example, more than 80% of the farmland in Sub-Saharan Africa is plagued by severe degradation which in turn is a major cause of poverty and hunger in sub-Saharan Africa, where one in three people is undernourished 4.
Second, while an initial response to lack of natural nutrients is to use fertilisers, in the long-term this can increase and worsen the problem. One key reason for this is that fertilisers and pesticides can pollute local water resources and harm wildlife. It is also important to note that eroded soil also finds its way into rivers, lakes and coastal areas. Sedimentation causes serious damage to freshwater and marine habitats, as well as the local communities that depend on these habitats.
For example, the people of Xingu Indigenous Park in Brazil have reported declines in fish numbers, a trend which is attributed to changes in the courses of waterways resulting from farming-related erosion and the silt deposition this causes 2.
What is more, soil erosion increases the risk of flooding as soil is no longer there to absorb the water.
Ways to reverse the effects of over-cultivation
This is not to say that there is no way to reverse the effects of over-cultivation if proper action is taken on time. For example, practices that encourage crop rotation and fallow periods can help minimise soil erosion and degradation. By growing different crops each year, it is possible for soil nutrients to be replenished while fallow periods, that is time when the land rests, give the soil time to renew its fertility.
To minimise soil erosion and conserve water, land managers can plough taking into account the shape or contour of the land rather than against it. Similarly, shelter belts – otherwise known as wind breaks – are areas of forest or hedge that are left untouched to protect farmland from the effects of water and wind erosion. In addition, by reforesting or afforesting areas you can help return land to its natural state, making it more fertile and stable, thus reducing wind and water erosion and ultimately land degradation.
So there are remedies to minimise the effects of over-cultivation. This is important to highlight as arguably; over-cultivation doesn’t just happen in response to market pressures; evidence shows that over the years we have been adopting and implementing the wrong kinds of policies that have perpetuated the need to over-cultivate our lands.
One such example is the Agri Basin in Southern Italy where changes in agricultural subsidies during the 1980s encouraged the intensification of land use and expansion of irrigation practices. By artificially increasing the profitability of wheat production, and decoupling the durum wheat subsidy from yield to land-area, land unsuitable for tillage was encroached upon, leading to soil degradation and erosion, land abandonment and desertification 5.
Luckily, there are many solutions we can implement to minimise the instances of over-cultivation. Organisations such as the UN FAO or work around the UN 2030 Sustainable Development Goals is critical to understanding how we can reform our agriculture and food systems to make them more sustainable. There is certainly time to make our agriculture more sustainable by 2030!