How do earthworms help the world's food production grow by 140 million tons per year?

Soil is the foundation of all things. 95% of human food comes from soil. American soil scientist Albrecht pointed out that soil lacking organic matter, major elements and trace minerals will cause crop failure and human health problems. At present, about one-third of the world's population suffers from "hidden hunger", which is malnutrition caused by unbalanced intake or lack of necessary micronutrients. my country also faces this challenge.

As the cornerstone of soil health and the engine of soil function, soil animals participate in almost all important soil ecological processes, silently supporting the health and sustainable development of the earth's ecosystem. Among them, earthworms are particularly important, accounting for 60% of the biomass of soil fauna, and were praised by Darwin as creatures that "play an irreplaceable and important role in the course of world history." They accelerate the decomposition of organic matter through behaviors such as swallowing and burrowing, and mix surface fallen leaves and soil into deep soil, increasing the absorption of nutrients by plants.

Earthworms contribute up to 25% of the world's food production, and more than 140 million tons of food are produced each year due to earthworms' "farming"! Unfortunately, due to their unattractive appearance, earthworms have not been taken seriously. In fact, the importance of earthworms lies not only in their contribution to food, but also in protecting soil and human health in many aspects.

1. The hardworking "simple farmer"
Earthworms live in the soil and feed on it. When they wriggle in compacted soil, they can form up to 800 burrows per square meter. These burrows not only increase the air permeability and looseness of the soil, but also promote the formation of soil aggregate structure, effectively regulate soil water and fertilizer, and affect soil microorganisms and enzyme activity. The feeding and excretion of earthworms play a key role in the redistribution of energy in the soil. In tropical savannas, 20 earthworms per square meter take in a total of 11,750 kilojoules of energy per year and excrete 10,700 kilojoules. The particle size of their feces matches the aggregate structure of high-quality soil, and the higher porosity also helps maintain soil structure. Therefore, earthworms are considered to be the main force in maintaining soil structure.

Figure 1 Earthworm holes (left, photo by Zhao Qi) and earthworm feces (right, photo by Jiang Jibao)

2. The unknown “good doctor”
Soil is a "living organism". Although it has a strong buffering capacity, long-term high-intensity cultivation and damage can still cause "diseases". At present, the total area of ​​saline-alkali soil in my country is about 1.5 billion mu, 2 million tons of plastic mulch remain in the cultivated land, the rate of excessive heavy metals in the soil is 19.4%, and the average detection rate of antibiotics in the 0-20 cm surface soil is as high as 58%!

As the "natural doctor" of the soil, the activities of earthworms can strongly affect soil properties, change the structure and diversity of soil microbial communities, and prevent and treat soil problems. Its unique intestinal environment: neutral pH, anaerobic, high quantity/high quality substrates and local microbial communities, is the best place for pollutant degradation. Earthworms also have a detoxification enzyme system that effectively alleviates soil heavy metal pollution and promotes the degradation of antibiotics and pesticides.

Our research found that Metaphire guillelmi, a common earthworm in Shanghai farmland soil, can increase the degradation rate of tetracycline antibiotics by 13.7% to 29.0%, while increasing the total nitrogen, available phosphorus and total potassium content. In addition, earthworms can promote the degradation of roxarsone and enhance the arsenic reduction and methylation functions of the soil. In saline-alkali farmland soil, earthworms and fungi work synergistically to reduce soil pH and promote nitrogen absorption by crops. Earthworms also grind large plastic particles through their gizzards and use microplastic-degrading bacteria to degrade microplastics, thereby slowing the spread of resistance genes (ARGs) in the soil.

However, earthworms are not King Kong. When pollutants exceed a certain threshold, the lives of earthworms will be threatened. At this time, who will protect our health? !

3. “Recycling Specialist” who turns waste into treasure

As an important decomposer in the ecosystem, earthworms are not picky eaters. In addition to soil, they also eat dead branches and leaves, kitchen waste, livestock and poultry manure, etc. Earthworms can consume about 1.0 to 1.7 times their own body weight in food every day, and excrete about 0.5 times their body weight in earthworm manure. Because it is rich in nutrients and easy for plants to absorb and utilize, earthworm manure is known as the "king of organic fertilizer." According to statistics, earthworms per acre of land can consume 400 tons of organic waste each year, and 1 ton of manure can breed 60 to 70 kg of earthworms and produce 300 to 500 kg of earthworm manure.

Figure 2 Earthworms processing cow dung

my country is a major agricultural producer. While meeting the food needs of 1.4 billion people, it also produces more than 4 billion tons of organic waste annually. Although my country has carried out comprehensive utilization of crop straw and livestock and poultry manure, the disposal rate of organic waste in some regions is still low, which is far from the goal of high-quality agricultural development in my country. Therefore, using earthworm composting technology to improve the current status of agricultural waste treatment can better achieve the diversified utilization and harmless effect of agricultural waste and promote the circulation of nutrient elements.

4. Natural and healthy “medicine and food have the same origin”

Audiences who have watched the movie "The Wandering Earth" must have been impressed by the scene where "people in the underground city give dried earthworms as gifts." Compared with common high-protein foods, the protein content of earthworms can reach 54.6%~59.4% (in terms of dry matter), which is about 1.55 times that of soybeans and 5 times that of eggs. Its amino acid content is also far higher than that of fish, dried fruits and beef liver. Earthworms are also rich in a variety of vitamins, minerals and trace elements. Adding about 5% of earthworms to animal feed can significantly promote the growth of livestock and poultry, enhance immunity, and improve the quality of meat and eggs. In the context of the lack of protein source feed in my country, using earthworms as protein raw materials is one of the effective ways to solve protein dependence.

Medicine and food have the same origin. Earthworms have a long history of use as traditional Chinese medicinal materials. Earthworms were already mentioned in the Shennong's Herbal Classic. However, only four types of dried earthworms are recognized as earthworms by the Pharmacopoeia of the People's Republic of China (2020 edition), namely Amynthas pectinifera, Metaphire vulgaris, and Amynthas aspergillum. Earthworms mainly contain amino acids, bases, nucleosides, fatty acids and other substances, and have anti-thrombotic, anti-tumor, anti-hypertensive, immune regulation, and wound healing effects. In addition, lumbrokinase, an extract of Eisenia foetida, has also been used clinically to inhibit thrombosis and improve cerebral ischemia.

Figure 3. Earthworm (Photo by Jiang Jibao)

V. Conclusion

As of now, there are more than 6,000 species of terrestrial earthworms in the world, and 706 species in my country. However, with the development of industrialization and urbanization, the living areas of earthworms and other organisms are constantly compressed, and the living environment is getting worse. The occurrence of electric earthworm capture incidents has led to a sharp decrease in the diversity of soil animals such as earthworms, which in turn affects soil quality and plant health. In order to obtain enough food, farmers have to apply more fertilizers and pesticides, which will further aggravate the damage to the soil and form a vicious cycle. The balance between organisms and the natural environment is the result of millions of years of evolution. It is both harmonious and fragile. If we dry up the pond to fish and burn the forest to hunt, we will eventually break the ecological balance and affect human survival.

In order to protect arable land, agriculture and ourselves, the road to "saving earthworms" has begun. In 2022, seven departments including the Ministry of Agriculture and Rural Affairs, the State Forestry and Grassland Administration, and the State Administration for Market Regulation jointly issued the "Notice on Strengthening the Protection of Wild Earthworms and Improving the Soil Ecological Environment". We also joined hands with the Changning Procuratorate of Shanghai and the Pinduoduo platform to participate in the "Green Net Plan" to protect earthworms. In 2023, the Central Document No. 1, "Opinions of the CPC Central Committee and the State Council on Doing a Good Job in Comprehensively Promoting Key Work on Rural Revitalization in 2023", proposed for the first time "severely cracking down on theft of black soil, electric capture of earthworms and other acts that damage the soil". In June of the same year, the State Forestry and Grassland Administration also included four species of earthworms with high utilization intensity and high resource consumption in the "List of Terrestrial Wildlife with Important Ecological, Scientific and Social Value".

As researchers who have been engaged in earthworm research for a long time, we have traveled to various parts of the country every year for the past 20 years to investigate earthworm resources, and have obtained more than 100,000 specimens from more than 3,500 sampling points. In 2019, we established the only earthworm specimen museum in the country, where all collected specimens are preserved to provide strong support for the protection of earthworm species diversity. At the same time, in order to break the public's stereotypes about earthworms and stimulate the public's attention to earthworms and the ecological environment, we created a popular science public account in 2022 - "Earthworm Words", and carried out related science popularization through platforms such as the Maritime Science Popularization Forum, Super Star Master Forum, Shanghai News Radio, and Shanghai Natural History Museum.

Of course, protecting earthworms requires a concerted effort and long-term persistence. Relevant departments should improve laws and regulations, and the general public should also enhance their awareness of protecting biodiversity. Earthworms are secretive and great underground elves. Protecting earthworms is protecting the land on which we depend for survival and our home. Only by respecting nature, adapting to nature, and protecting nature can we protect the overall health of mankind!