Soil is a complicated medium formed through biological and geological processes. It is on land on the uppermost layer of the Earth's crust. Currently, there is a high risk of losing the arable soil that supports agriculture. Needless to point out the importance of agriculture, which solely feeds the growing global population. The current article discusses the factors that increase the growing threat of soil extinction.
Why The World Is Running Out Of Soil
Soil is an important reservoir of biodiversity. It harbors almost one-quarter of all living organisms that exist on the planet. Soil provides various services, such as supporting life on the planet, regulating water movement and climate, generating biomass, and biogeochemical cycling. However, these services depend on soil biodiversity. Soil biodiversity is often a determinant of soil condition and susceptibility to extinction.
For healthy soil, it is important to maintain ecosystem diversity (different types of habitats present in the soil), genetic diversity (combination of different genes found within a population), species diversity (different types and abundance of organisms inhabiting a soil), phenotypic diversity (various morphological, physiological and biochemical aspects of soil microbes), and functional diversity (variable microbial functions, such as nitrification and carbon turnover).
What is Soil Extinction?
Historically, the Earth's soil has been rich in organic content and beneficial organisms. However, in modern times, the significant decrease in the organic content of the soil, which supports the biological content, is alarming.
The organic content of the soil is composed of humus, which is basically a conversion of life forms into the soil, i.e., the plants' litter (e.g., leaves and other parts) or even animal droppings. Healthy soil must be covered with vegetation, such as crops, trees, herbs, and shrubs. However, in modern agricultural practices, the entire soil diversity and its organic content gets disturbed after harvesting. Furthermore, often the land is kept bare and exposed after harvest, which leads to soil extinction.
Soil extinction occurs due to the loss of organic and biological content and its conversion to sand. Typically, soil requires 3-6% of organic content to stay healthy; however, recent data revealed that 62% of Indian and 75% of European soil contain less than 0.5% and 2% of organic content, respectively. The US has lost almost 50% of its topsoil. Globally around 52% of agricultural soil has been lost, and if a similar trend continues, 90% of Earth's soil could be lost within the next 30 years.
Factors Associated with Soil Extinction
Rapid conversion of natural ecosystems to farmland leads to soil extinction. Many agricultural sectors do not practice soil conservation, which causes the loss of precious soil due to salinity and erosion at an increased rate. In the US alone, agricultural soil is getting eroded 10-15 times faster than it can be replenished. The United Nations Food and Agricultural Organization (FAO) announced that one-third of global soil has undergone moderate to severe degradation.
Soil degradation results from aggressive tilling and lack of off-season plantation, which exposes the topsoil to wind and water. Additionally, accumulating unused fertilizers and salts from irrigation can make arable land unusable. Plant growth in degraded soil is extremely difficult and would contain less nutrition than in healthy soil.
A loss of soil biodiversity can reduce soil's resistance to perturbation and affect its capacity to recover. A decline in soil diversity typically affects the soil's ability to function normally and respond to perturbations. Soil experts have highlighted some factors that enhance the risk of soil biodiversity loss, including land-use change, human-intensive exploitation, soil pollution (e.g., plastics), soil erosion, habitat fragmentation, soil compaction, climate change, genetically modified organism (GMO) pollution, invasive species, and soil organic matter decline.
Soil pollution occurs from a variety of sources, including industry, agriculture, transport, and waste management. Soil contaminants, such as heavy metals, atmospheric deposition of nitrogen, and organic pollutants, have detrimental effects on soil biodiversity.
Soil salinization, which results from the over-abstraction of groundwater, threatens soil biodiversity. In addition, excessive use of fertilizers and municipal wastewater leads to structural damage of soil aggregates, soil erosion, and reduction in organic matter. All these events also adversely affect soil diversity.
Deforestation in tropical forests is another key driver of soil extinction as it impacts soil microbes, macrofauna, and mesofauna. Land use change leads to less diverse vegetation and the transformation of semi-natural ecosystems to mono-crop agriculture.
Image Credit: AlexanderLipko/Shutterstock.com
Prevention of Soil Extinction
Increased evidence on soil degradation and the risk of soil extinction are being documented. Scientists have formulated strategies that can prevent this condition. These strategies are discussed below:
One of the measures to prevent soil extinction is to reform farming practices and preservation of existing cropland soils. The use of green manure and leguminous soil cover could be effective soil conservation strategies. The biological content of the soil has a unique ability to resist events that could affect soil health. Soil microbes also can restore and recover degraded soil.
Monitoring of soil microbes
Analysis of soil microbes helps assess the soil condition, its extinction susceptibility, and current extinction status. Regular monitoring of soil microbes through molecular sequencing would provide a better picture of the organisms present in the soil. Identifying keystone below-ground taxa and establishing the network of their interactions enhances the prediction accuracy of soil health.
Molecular data combined with bioinformatic strategies help analyze below-ground communities. Furthermore, the development of improved below-ground extinction models, based on multi-parameters, such as fertilization pulses and tillage, will help to predict the soil condition better.
- Agarwal, V. (2022) We are facing soil extinction! What it is, why you must care. Times of India. [Online] Available at: timesofindia.indiatimes.com/.../
- Petruzzello, M. (2022) Could We Lose All the Soil on Earth? Britannica. [Online] Available at: https://www.britannica.com/story/could-we-lose-all-the-soil-on-earth
- Begum, T. (2021) Soil degradation: the problems and how to fix them. [Online] Available at: https://www.nhm.ac.uk/discover/soil-degradation.html
- Guerra, C.A., et al. (2020) Global vulnerability of soil ecosystems to erosion. Landscape Ecology, 35, pp. 823–842. https://doi.org/10.1007/s10980-020-00984-z
- Tibbett, M. et al. (2020). Identifying potential threats to soil biodiversity. PeerJ, 8: e9271. 10.7717/peerj.9271.
- Veresoglou, S. et al. (2015) Extinction risk of soil biota. Nature Communications, 6, 8862. https://doi.org/10.1038/ncomms9862