“The threat of nuclear weapons and man’s ability to destroy the environment are really alarming. And yet there are other almost imperceptible changes – I am thinking of the exhaustion of our natural resources, and especially of soil erosion – and these are perhaps more dangerous still, because once we begin to feel their repercussions it will be too late.”
Soil is the earth’s fragile skin that anchors all life on Earth. It is a mixture of minerals, organic matter, gases, liquids and innumerable life supporting elements creating a complex and dynamic ecosystem comprising of countless species. It is clearly among the most precious resources to humans and animals alike.
Soil erosion is a natural process that refers to the wearing away of the top layer of soil by action of wind and water, and this normal process has been continuing for some 450 million years, ever since the first land plants formed the first soil during the Silurian Period. In general, the soil removed by this “background” soil erosion is roughly at the same rate at which soil is formed. But ‘accelerated’ soil erosion — loss of soil at a much faster rate than it is formed — is a far more recent problem. Half of the topsoil on the planet has been lost in the last 150 years. A study estimated that around 15 per cent of the Earth’s ice-free land surface is afflicted by all forms of land degradation. Of this, accelerated soil erosion by water is responsible for about 56 per cent and wind erosion is responsible for about 28 per cent.
This means that the area affected by water erosion is, very roughly, around 11 million square km., and the area affected by wind erosion is around 5.5 million square km.
Major causes of soil erosion include deforestation, agricultural practices, overgrazing, and use of agrochemicals.
Deforestation is one of the major contributors to the problem of soil erosion. Without optimum plant cover, erosion can occur and sweep the land into rivers. The roots of trees tend to hold on to the soil. However, the agricultural crops such as coffee, cotton, palm oil, soybean and wheat are unable to hold the soil around them, worsening the erosion. The land loses it’s fertility as a result of the washed out top layer making it unsuitable for agriculture. As the farmers move on, they clear more forest for cultivation, and the cycle of soil loss continues viciously.
Agriculture is another culprit to be blamed for the loss of top layer of soil. The rampant and unplanned agricultural practices replace natural vegetation, exposing the top soil, leaving it to dry out. The diversity and quantity of microorganisms that help to keep the soil fertile can decrease, and nutrients may wash out.
Pasture lands that were initially natural ecosystems do not seem to be damaged to a large extent in the first look, but this change in usage of land can lead to high rates of erosion and loss of topsoil and nutrients. Overgrazing enables the erosion and compaction of land by wind and rain as it reduces ground cover. Further, the soil microbes are harmed as the ability for plants to grow and the water to penetrate is reduced, leading to more soil erosion.
Widespread use of pesticides and chemicals to increase the yield of crops is another factor responsible for soil erosion. Scientists have found that overuse of some of these chemicals changes soil composition and disrupts the balance of microorganisms in the soil. As a result, the growth of harmful bacteria is stimulated and encouraged at the cost of the beneficial kinds.
Other than these intensive agriculture, deforestation, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion.
The impacts of Soil Erosion include desertification, loss of arable land, clogged and polluted waterways, and increased flooding.
Desertification refers to a type of land degradation where a relatively dry land loses it’s bodies of water, vegetation, and wildlife, and becomes increasingly arid. These areas can be characterised by the droughts and arid conditions the land endures as a result of human exploitation of fragile ecosystems. Desertification not only leads to further soil erosion and sterility, but it’s other effects include land degradation, soil erosion and sterility, and a loss of biodiversity, with huge economic costs for around 168 nations where these deserts are growing.
The loss of arable land that can be used to grow crops is another impact of soil erosion. Many of the agricultural practices lead to the loss of fertility as they remove the top fertile layer of soil. The UN’s Food and Agriculture Organisation (FAO) predicts that the demand for food will increase 60% by 2050. Experts say that the world will need an additional 120 million hectares of agricultural land to support the required food production – that is a new farm the size of South Africa. Efforts to boost agricultural production often lead to rampant agricultural practices, a major contributor to soil erosion.
Soil eroded from the land, along with the chemical pesticides and fertilisers applied to fields, runs off and mixes with the water sources such as streams and other waterways. This sedimentation and pollution damages fresh water and marine habitats and also poses a threat to the local communities that depend on them. Severely impacted species include the sea turtle which has been declared endangered because of habitat destruction.
Soil erosion can lead to increased flooding. The pasture lands and crop fields converted from forests or other natural landscapes, such as floodplains and wetlands are less able to soak up water, increasing the risk for flooding.
Soil erosion remains a key challenge for the environmentalists worldwide. Other environmental concerns such as climate change and shifting weather patterns will only magnify the existing wind and water erosion situations and create new and worse areas of concern. Farmland must be protected and agricultural practices should be made as sustainable as possible. Special attention should be focussed upon situations of higher risk that leave the soil vulnerable to erosion.