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Although soils are vital for agriculture, biodiversity, and clean water, this underground world is often overlooked. The loss of life underground due to intensification of agriculture, climate change, erosion and compaction, among other things, is one of the greatest global threats to soils.
Many organisms live in the soil. In fact, about 25% of all biodiversity is in the soil. These organisms do not function in isolation, but interact with each other and with the surface world in complex ways. They provide essential services and benefits, such as the decomposition of litter for nutrient cycling, play a role in the formation of soil structure, and clean water and air through soil layers.
With an increase in extreme events like heat waves and droughts due to climate change, soil is increasingly degrading around the world. Organisms and the soils in which they live are dying. Another reason is the increased demand for food production through more intensive agriculture and compaction, when soil particles are pressed together, reducing the space between soil particles, reduces the infiltration of water and air into soil.
But if there is a change in the way soils are managed, more resilient and sustainable soils can be created that can survive these increasing extreme events and improve food security. This means that the soil will recover after extreme events. You will not need as many fertilizers and pesticides and will be able to maintain long-term production of high-quality food.
The theme for this year’s World Soil Day on December 5 is: “Keep Soil Alive, Protect Soil Biodiversity.” It coincides with the publication of the report on the state of knowledge of soil biodiversity. This report, facilitated by the Food and Agriculture Organization of the United Nations (FAO), involved more than 300 scientists from around the world, including myself. It highlights the rich diversity of soil organisms under our feet that drive processes that produce food and purify soil and water.
Soil biodiversity in Africa
The springtail (Seira species) from South Africa. Provided by the author. Photo by: Amy Liu
Soils are the most biologically diverse habitats on earth. One gram of soil contains several thousand different species. More than 40% of all terrestrial organisms have their life cycle, or part of it, in the soil. These range from the smallest microbes, fungi and nematodes, to mites, springtails, centipedes, millipedes, potworm worms, various insects such as ants and termites, larger arthropods such as millipedes, spiders, and mealybugs, and even larger vertebrates such as moles and reptiles. .
During the last decades, there has been an increased interest in soil health globally and in South Africa. This comes after events such as massive droughts, erosion, and studies of the role of soil organisms in soil health and more awareness campaigns.
Read more: Dust in the atmosphere is a sign of trouble in South African corn fields
Despite the fact that South Africa is only 0.8% of the earth’s land area, it contains almost 1.8% of the world’s described soil species. South African soils contain a very large number of species found nowhere else in the world, especially nematodes and earthworms, although these are groups that have been studied more than others.
Knowledge of the soil biota in South Africa, such as spiders, ants, termites and mites, is increasing, while other groups such as diplurans and collembola (small wingless invertebrates) are poorly studied. Their small size may be one reason why they are often overlooked, but identifying these little animals is also difficult. The expert skills necessary to identify them are limited. Mite species: Acari, Anystidae family (left). Springtail: Collembola, family Dicyrtomidae standing on snail eggs (right). www.chaosofdelight.org. Provided by the author. Photos by: Andy Murray
But with increasing international collaborations, more is being learned about these overlooked underworld workers. Collembola have been increasingly studied because they are good indicators of soil health. They respond quickly to changes in the environment and are sensitive to changes. They mainly feed on decaying plant material, bacteria, and fungi, so they play an important role in the decomposition process.
Many new species have been discovered in South Africa, but their functional functions in natural and even “simple” agricultural ecosystems are only now being investigated.
Threats and challenges
Much of Africa’s soils are severely degraded, while several million tonnes are lost each year through soil erosion.
Several human activities have been identified in the State of Knowledge Report on Soil Biodiversity as major threats to biodiversity and soil functioning in Africa. These include deforestation, agricultural intensification, loss of soil organic matter and soil organic carbon, climate change, fire, soil compaction and sealing, salinization, erosion, and invasive species. Furthermore, there is a lack of knowledge about the impacts of these threats and this may hinder sufficient management to conserve this underground system.
Why is soil biodiversity important?
Soil biodiversity contributes to healthy soils, provides many ecosystem services and, in turn, achieves compliance with (among others) the following Sustainable Development Goals:
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Food production: the link between soil and food is very clear. Food security in Africa is a great challenge. Crop quality and yield are directly related to soil health.
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Water quality: Soil biota plays an important role in regulating the movement of water into and through the soil, as well as in the cycling of nutrients in soil and water. Poor soil quality can increase the risk of nutrient loss through leaching and water runoff, which can lead to groundwater contamination.
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Air quality: increased tillage can increase the production of carbon dioxide by microbes that can contribute to global warming. Certain microbes in the soil can release methane from the soil or transform nitrate into nitrous oxide, a greenhouse gas. On the other hand, soil microbes and fauna can improve soil structure and reduce the risk of wind erosion.
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Climate change mitigation: Since agricultural soils cover a large part of the world, agricultural practices such as reducing tillage and increasing vegetation cover can improve soil biological activity and carbon sequestration.
A step in the right direction is to raise awareness about the importance of soil biodiversity and practice conservation agriculture, that is, use minimum or zero tillage, have a crop rotation system and permanent soil cover (hence , residues remain after harvest).
A fundamental understanding of soil biodiversity in Africa is needed, especially if applied soil research is to be effective in ensuring resilient soils. For South Africa, this means more integrative research, training more taxonomists to describe the large number of unknown species, and funding to gain knowledge of soil biodiversity in this mega-diverse region.
Charlene Janion-Scheepers receives funding from the National Research Foundation (South Africa).
By Charlene Janion-Scheepers, Professor of Biological Sciences, University of Cape Town
