It’s that time of the year again, when many in the drier Sahel of West Africa experience dust storms. And the dust is everywhere!
Dust generally consists of fine particles of solid matter from various sources such as the soil, pollution and volcanic eruptions. Interestingly, 20–50 percent of dust in our homes consists of dead skin cells, while the rest (especially in offices) consists of plant pollen, textile and paper fibers, human hair and animal fur, to name a few.
Aeolian dust (atmospheric dust, or dust carried by the wind) is probably the most obvious category of dust. Aeolian dust comes from arid and semi-arid regions where winds remove dust particles and transports them to the lower part of the atmosphere called the troposphere. An estimated one-third of the earth’s land area consists of dust-producing surfaces such as deserts (for example, Sahara desert, with an area of 9 million sq km) and the so-called drylands of the world which cover 52 million sq km.
The phenomenon of atmospheric dust should be seen in the context of the broader issue of soil erosion, which is a form of soil degradation, and displacement of the upper layer of the soil. Soil erosion is a natural process caused by agents such as water (both liquid and ice [as glaciers and snow]), wind, plants, and animals (including human beings). Soil erosion may be a slow, natural process, or it can be accelerated, resulting in huge loss of the top and most fertile part of the soil.
Soil erosion is a big problem because a conservative estimate of 75 billion tonnes of fertile soil are lost from agricultural systems annually. Only 38 percent or 5 billion hectares of the global land surface is classified as agricultural land. Of this, only one-third is used for crops, while the remaining two-thirds are used for grazing livestock. Furthermore, the process of soil formation is very slow; taking as much as five hundred thousand years for one inch or 2.5 cm of soil (which can be washed away by one heavy rain) to be formed from rock. The precariousness of humanity’s dependence on soils, and the threat posed by un-controlled soil erosion is also underlined by the fact that 99.7 percent (in terms of calories) of human food comes from the land.
The Sahel region of Africa has been vulnerable to the impact of climate change on the amount and distribution (over time) of rainfall. In The Gambia, which is in the wetter southern fringes of the Sahel, the length of the rainy season has been reduced by about 15 to 30 days, and the area of the country receiving less than 800 mm of rainfall from July to September decreased from 36 percent in 1965 to 93 percent in 2005. This, coupled with the average increase in temperature of 0.21 degrees Celsius per decade since the 1960s means that Gambian soils, like those in the rest of the Sahel, have been increasingly desiccated, making them more vulnerable to being eroded by the harmattan winds which blow in from the Sahara desert during the dry season.
Sahelian countries have also worked hard at increasing agricultural production and productivity, often through mechanisation, and increasing the area of cultivated land. These strategies have, however, frequently backfired because the generally poor soils in the area are easily destroyed by heavy equipment, and much of the increase in cultivated lands is often accounted for by marginal fields which have relatively low productivity.
As it happens, Sahelian countries can learn a lot from the so-called Dust Bowl of the United States of America (US). Back in the 1930s, a combination of poor farming practices and the effects of severe droughts damaged the prairies (vast expanses of grassland) in the Great Plains of the US and Canada. As a result, huge dust storms turned the Great Plains into the Dust Bowl that some called hell on earth. In May 1934, one of the worst dust storms of the period of the Dust Bowl went as far as the eastern US, 2,400 km away, and dumped about 5,500 tonnes of dust on Chicago. The Dust Bowl affected an area of 400,000 sq km, more than the land area of Senegal, Togo, Guinea Bissau, The Gambia and Cape Verde combined.
Sahelian dust storms are mainly caused by human activities such as overgrazing and cultivation of marginal lands by subsistence smallholder farmers, resulting in a downward spiral of environmental degradation and impoverishment, often called the Sahel Syndrome. Some of these dust storms reach 5 to 6 km in height, and are occurring with increasing frequency. As such, severe dust storms often, especially during the dry season, blanket the West African Sahel as in 2010, 2012, and as recently as 2021. Together with the Sahara Desert, the Sahel is the largest source of dust in the world, producing 790–840 million tonnes of dust per year.
Dust from the Sahara Desert and the Sahel is transported as far as Europe, the US, the Caribbean, and the Amazon basin in Brazil. The dust storms cause health and environmental problems both in the Sahel and other countries where the dust ends up. Thus, dust can cause or aggravate respiratory disorders such as pneumonia, asthma, and bronchitis, as well as eye infections, cardiovascular disorders (e.g. stroke), and skin irritations. Dust storms also cause meningitis, hence the reason why 26 Sahelian countries from Senegal to Ethiopia are called the “meningitis belt.” Similarly, Sahara Desert and Sahelian dust transported across the Atlantic Ocean to Europe and the Americas has been found to carry microorganisms, some of which might be harmful to human health.
Sahelian and Sahara Desert dust dumped on the Americas carry a lot of nutrients, which effectively serve as fertilizer for these areas. Ironically, Senegal, Mali, and Burkina Faso collectively imported 8.1 million tonnes of fertiliser between 2010 and 2019. Of the 182 million tons of dust carried annually by dust storms from the Sahara and the Sahel, about 28 million tons are dumped on the Amazon basin, and about 43 million tons are deposited on the Caribbean Sea.
Given that the dust contains valuable plant nutrients, its loss constitutes a significant drain on the fertility of soils in the Sahel. On the other hand, the nutrients in the dust deposited on waters in the Caribbean and Eastern US, increase the population of microorganisms called red algae. These organisms turn the sea red (hence then term “red tide”), and produce toxins that are harmful to fish.
The impact of climate change and increasing pressures on land resources in the Sahel means that it is imperative that efforts are redoubled to reduce dust storms. This is especially so given the increased frequency and size of these storms. In this regard, it is worth noting that the Great Green Wall (GGW), conceived in 1986 by the late former leader of Burkina Faso, Thomas Sankara, is now being implemented by initiative of the African Union. The GGW is aimed at stopping the southward spread of the Sahara Desert by planting a 15 Km-wide, and almost 8 thousand Km long belt of trees from Senegal to Ethiopia.
It is also important to learn the US Dust Bowl was caused by the increased mechanization and extensive application of chemicals on lands that were not capable of sustaining such practices. Although there is room for mechanisation of agriculture in the Sahel, it must be thought through, and the technologies used should be appropriate to climatological and land resources realities on the ground. In this regard, it is important to ensure that agro-ecological and sustainable approaches to agricultural production are taken on board.
Given that the increase in dust storms in the Sahel is driven by subsistence agriculture, and that Sahelian soils are generally of low fertility, efforts must be made to increase fertilizer production in the region by, for example, using Nigerian natural gas, which is currently flared (burned) off. Furthermore, research capacities should be developed, collaborative research conducted to get a better understanding of dust storms in the Sahel.
Although dust storms have, since time immemorial, been an important feature of the Sahelian landscape, a failure to address the increased threat they pose to sustainable development in the Sahel could, for the people of the region, spell the hell that many saw the US Dust Bowl as. And when you are a step from hell, you should take a step back and rethink your strategy.
