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Soils of Africa and the quality

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Jacopo Parigiani & Samantha Spooner

Soils of Africa and the qualityTHE United Nations has declared 2015 as the “International Year of Soils”, and with good reason. Soil is one of the most important resources that we have, if not the most important.

It sustains all our agricultural and livestock food production, wood for fuel production, filters water so that we can drink it and fish can live in it. We also use it for construction – therefore it sustains our homes and infrastructure. Soil is a crucial aspect of African economies yet many Africans are forgetting this.

With an increasingly urban society, many people are losing contact with the processes of food production, expecting to find goods on the shelves of supermarkets and have limited or even no appreciation of the role played by soil. Politicians and policy-makers are also out of the loop since the majority of soil-related print material is geared towards university level or scientific journals and out of the reach of the general public.

Soils of Africa and the quality 2Unfortunately, even in the Comprehensive African Agriculture Development Programme (CAADP), Africa’s policy framework for agricultural transformation, land degradation is not prioritised or reflected in the form of concrete financial commitments and projects.

A quick soil refresher:  All soil is composed of mineral particles (sand, clay and silt), organic matter, air and water.

It is a “living” system in that it breathes. In fact, a healthy soil reduces the impact of climate change, storing up to 10% of the world’s CO2 emissions! Even though soil is such an integral part of our lives, it is extremely fragile.

The most productive (fertile) part of the soil is only a couple of centimetres thick, this is usually the part that is eroded first. 2.5cm of topsoil takes between 500 – 1000 years to form. Today soil is a threatened resource, precisely because soil erosion is so pervasive and hard to reverse. Here are six chilling facts on soil today:

Globally, we have about 60 years of topsoil – the layer that allows plants to grow – left.

Half of the topsoil on the planet has been lost in the last 150 years. In Africa, soil erosion has reduced Africa’s grain harvest by 8 million tons, or roughly 8%. This is projected to double to 16 million tons by 2020 if soil erosion is not reduced. Ethiopia alone loses one billion tonnes of topsoil every year.

Land degradation costs sub-Saharan Africa $68 billion per year

Africa is perhaps the continent most severely impacted by land degradation; 65% of arable land, 30% of grazing land and 20% of forests are already damaged. Land degradation varies widely though in some countries the extent is staggering. In Ethiopia, over one-quarter of land is degraded, which affects about 20 million people, just under a third of the total population, while in South Africa 40% of all cropland suffers from land degradation.

In the Congo and Zambesi basins 24%-29% of land is degraded whilst in the dry areas of Niger and Lake Chad basins, up to a high 78% to 86%. Below are the variety of factors which all influence soil degradation:

Population pressure is going to exacerbate this issue as more and more marginal soils are put into cultivation; current trends predict that almost 2 billion babies will be born in Africa in the next 35 years.

Aridity and desertification affects half of Africa

Almost all countries in Africa are susceptible to desertification but the Sahelian countries at the southern fringe of the Sahara desert are particularly vulnerable, with pockets of very high risk areas. Unless the desertification of this region is halted, within the next 20 years some 60 million people will be leaving the region – refugees from the desert. It has been estimated that 319 million hectares of Africa are vulnerable to desertification hazards due to sand movement, including desert movement at an annual rate of 5 km in the semi-arid areas of West Africa.

Nutrient mining affects more than 75% of the continent’s farmland

African farmers have traditionally cleared land, grown a few crops and then moved on to clear more land. This results in “nutrient mining” which affects 95 million of Africa’s 220 million hectares of farmland, losing at least 30kg of nutrients per hectare (ha) every year. These losses, combined with soil erosion, have led to soil degradation and now more than 80% of Africa’s soils having chemical or physical limitations that impede crop production. The highest rates of nutrient depletion — more than 60 kg/ha yearly — are in Guinea, the Democratic Republic of the Congo, Angola, Rwanda, Burundi and Uganda. The impact has been a declining trend of per capita food production in Africa over the past 40 years.

Up to 30% of forests will disappear by 2030

The rate of deforestation in Africa is accelerating – in just ten years, 9% of forest cover was lost across sub-Saharan Africa. Slash and burn agriculture (putting down areas of forest and moving to other areas) was actually sustainable in the past but is not anymore due to population pressures. The main threat however is charcoal production – in Africa 90% of wood consumed is used for wood fuel and charcoal. In Central Africa alone between 1990 – 2000, approximately 91,000 km2 was lost to deforestation. As seen in the image below, without tree roots to anchor soil and with increased exposure to sun, soil can dry out, leading to problems like increased flooding and inability to farm.

Soils under tropical rainforests in Africa are also not naturally fertile but depend instead on the supply of organic matter from natural vegetation.

Overgrazing is responsible for about half of the soil degradation in Africa

Overgrazing leaves soils bare of vegetation, at the mercy of the elements, it also compacts the soil, inhibiting water infiltration in the ground – meaning water runs off on the surface and does not recharge groundwater. One of the worst affected countries in Africa is Ethiopia. Ethiopia’s estimated livestock population is often said to be the largest in Africa, with 80-85% of their food source being natural grazing.



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