Today marks World Soil Day (WSD) to celebrate the importance of soil as a precarious component of the natural system and as a vital contributor to human well-being. Dec 5, the birthday of HM the late King Bhumibol, was officially recognised as WSD by the UN in 2016 in memory of Thailand's great monarch.
The theme for WSD 2019 is "Stop soil erosion, save our future". Erosion is putting our soils in danger. Soil erosion is a major land degradation process that causes environmental and property damage, loss of livelihoods and services, as well as social and economic disruptions. As the human population has expanded, more and more land has been cleared for agriculture and other pursuits that degrade the soil and make erosion more likely to occur. Erosion not only lowers the quantity and quality of soils on-site, but also causes significant sediment-related problems off-site. Erosion causes the loss of the most fertile part of soil, substantially reducing fertility and having an adverse impact on agricultural production. Furthermore, it is almost impossible to repair badly degraded soil to its original state.
WSD 2019 and its accompanying campaign aim to raise awareness on the importance of sustaining healthy ecosystems and human well-being by addressing the increasing challenges in soil management, reducing soil erosion and raising the profile of healthy soil by encouraging governments, policymakers, organisations, communities and individuals around the world to engage in proactively improving soil health.
It is estimated that 95% of our food is directly or indirectly produced on our soils. Soils have a broad range of functions, many of which are vital to society and the environment. Biophysical soil functions include nutrient- and water-cycling, chemical filtering and buffering, physical stability, support of plant systems and human structures, and promotion of biodiversity and habitat.
Soil is our life support system. Soils provide anchorage for plant roots, while holding water and nutrients. They are home to myriad microorganisms that fix nitrogen and decompose organic matter, and armies of microscopic animals as well as earthworms and termites. Earthworms are considered soil engineers because of their effects on soil properties and their influence on the availability of resources for other organisms, including microorganisms and plants. Soil plays a vital role in the earth's ecosystem. Without it, human life would be very difficult and we certainly would not have evolved from hunting-and-gathering cultures.
Soil filters the rainwater and regulates the discharge of excess rain, preventing flooding; it is capable of storing large amounts of organic carbon; it buffers against pollutants, including CO2. Soil protects groundwater quality.
Many people don't realise that healthy soil is full of life. The US Department of Agriculture defines soil health as "the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation".
There are four key concepts to remember when trying to develop healthy soil -- disturb the soil as little as possible; increase diversity using crop rotation; keep living roots in the soil as many days as possible during the year; and keep the soil covered as much as possible.
Millions of species and billions of organisms make up the complex and diverse mix of microscopic and macroscopic life that represents the greatest concentration of biomass anywhere on the planet. Bacteria, algae, microscopic insects, earthworms, beetles, ants, mites and fungi are among them. Altogether, their value has been estimated at $1.5 trillion a year worldwide. What these low-lying creatures lack in size, they make up for in numbers. Consider bacteria, the soil microbes with the highest numbers: you can fit 40 million of them on the end of one pin. In fact, there are more microbes in a teaspoonful of soil than there are people on the earth. These microbes, which make up only one-half of 1% of the total soil mass, are the yeasts, algae, protozoa, bacteria, nematodes and fungi that process soil into rich, dark, stable humus. The healthiest soils are those with a diversity and abundance of life.
Soil is an essential resource and a vital part of the natural environment from which most of the globe's food is produced. At the same time, soil provides living space for humans, as well as essential ecosystem services which are important for water regulation and supply, climate regulation, biodiversity conservation, carbon sequestration and cultural services.
The most important concept to grasp about soil is that it is a living system. A living system consists of life forms, and the food, air, water, habitat and shelter they need to thrive, grow and reproduce. In the soil, organic matter becomes food. The soil's structure and network of pore space provide habitat, air and water; and living vegetation and surface residues offer shelter for that habitat.
But soils are under pressure from population increase, higher demands for food, and competing land uses. Today the equivalent of one soccer field of soil is eroded every five seconds, and the planet is on a path that could lead to the degradation of more than 90% of all the earth's soils by 2050.
Although the importance of soils seems clear, in the past it did not received due attention in terms of its use and management, since soils were often considered an infinite resource that will always be able to provide us with their ecosystem services. However, this is not the case, and there is an urgent need to raise awareness on the importance of soil, especially the need to protect soils and use them sustainably.
A study conducted by Marina Sartori et al in 2019 estimates soil erosion causes $8 billion in global economic losses annually through reduced crop yields and increasing water usage. Climate change is making soil erosion worse. And certain countries are paying the price. As the climate changes, there are many more dry days interspersed with heavy rain. This leads to conditions where soil is more easily washed away during the deluges. Land use change by humans exacerbates water erosion, often by clearing out vegetation that helps hold soil together. Steep surfaces like hills can also contribute to the problem.
Researchers from the European Union Joint Research Centre coupled two models, RUSLE and MAGNET, to estimate economic losses from soil erosion by water. They found that $8 billion is lost annually from global GDP. Worldwide, food production is reduced by 33.7 million tonnes. The study is unique in that the researchers were able to capture losses from structural economic change as a result of shifts in primary resources, like land quality. Previous studies simply calculated crop loss and multiplied it by market values. Countries that have both the highest erosion rates as well as a large proportion of agricultural land are especially vulnerable. The majority of Caribbean countries, Brazil, Central African countries, and parts of Southeast Asia are experiencing severe erosion on more than 70% of their arable land. In contrast, Australia, Canada, Saharan countries, Russia, and most of the European Union are only losing 3% of their arable land to severe erosion. To put this in perspective, on average, 24% of arable land globally is undergoing severe erosion.
On WSD, we must focus our attention on being part of the solution. Small actions can have a significant impact on the health of our soils for zero hunger. Also, the best techniques to prevent or reduce soil erosion rates are to use land according to its capability, control runoff before it develops into an erosive force, reduced tillage and use conservation agriculture cropping systems, contour farming, terraces, plant forests on slopes, halt burning of crop residues, and leave vegetation including shrubs, trees, resistant grasses, cover crops and stubble.
Mohammad Esmaeil Asadi is associate professor of Water Engineering and Management, at the School of Engineering and Technology, Asian Institute of Technology.