Why are earthworms one of most important animals on planet?

• 6.5% of world cereal production and 2.3% of legumes depend on these annelids
• They can increase plant productivity by 25%, according to a study

Earthworms are crucial creatures for our planet and humans. They not only serve as food for many animals but also significantly contribute to global agricultural production as “ecosystem engineers”. According to data, earthworms are responsible for 6.5% of global cereal production (including corn, rice, wheat, barley) and 2.3% of legume production.

These percentages translate to over 140 million tons of food annually, which is comparable to the production of Russia, the world’s fourth-largest producer. Earthworms’ contribution is particularly significant in the southern hemisphere, contributing to 10% of total cereal production in sub-Saharan Africa and 8% in Latin America and the Caribbean.

The beneficial impact of earthworms (family Lumbricidae) on plant growth has been known since ancient times. However, their contribution to global agricultural production has only recently been quantified.

Researchers from Colorado State University in the United States conducted an in-depth analysis of the impact of these annelids on the global production of key crops. They examined maps of earthworm abundance, soil properties, and crop yields, along with scientific literature on the performance of these animals.

The research team’s findings are the first to quantify the contribution of a beneficial soil organism, in this case, earthworms, to global agricultural production. However, the researchers believe that other soil biota could be equally important and call for more studies.

Sustainability and resilience

The researchers do not advocate for the widespread introduction of earthworms in regions where they are not currently present, as this could have negative ecological consequences. Instead, they suggest investing in research and promoting agroecological management practices that enhance entire soil biological communities, including earthworms. This approach supports a range of ecosystem services that contribute to the long-term sustainability and resilience of agriculture.

Earthworms help establish “healthy soils” by supporting plant growth in various ways: they contribute to good soil structure, assist in water capture, and aid in the beneficial rotation of organic matter, making nutrients more available to plants.

Other studies have shown that earthworms facilitate the production of plant growth-promoting hormones and help protect plants against common soil pathogens. Some estimates suggest that earthworms can increase overall plant productivity by about 25%.

The three researchers Steven Fonte –lead author–, Nathan Mueller and Marian Hsieh estimated the contribution of earthworms to global food production by overlaying and analyzing maps of their abundance, soil properties, fertilization rates and crop yields.

Regarding their greatest impact in sub-Saharan Africa, Latin America and the Caribbean, Fonte considers it "likely" that earthworms have contributed more in those areas "because farmers there tend to have less access to fertilizers and pesticides. " Instead, they rely more on worm-rich organic matter, such as manure and crop residue, which helps stimulate the beneficial effect these animals have on plants.

Mitigate drought and erosion

"Earthworms are contributing a lot in these areas where we have less chemical inputs," highlights the main author. The researchers analyzed the impacts of earthworms on four cereal crops: rice, corn, wheat and barley, and on a set of legumes that included soybeans, peas, chickpeas, lentils and alfalfa, among others.

Fonte believes that soil biodiversity has historically been undervalued and that he hopes this work will bring more attention to how healthy soils can have positive and tangible impacts on crops.

"If we manage our soils more sustainably, we will be able to take better advantage of this biodiversity and produce more sustainable agroecosystems. This work highlights that potential," says the researcher, who highlights that other recent research has shown that soils contain up to half of the world's biodiversity, a significant increase from previous estimates of approximately 25%.

"Soils are a very complex habitat, but in reality, there have been very few efforts to understand what that biodiversity means for the global performance of our crops," he explains.

These researchers revealed information that could influence future efforts to mitigate drought and erosion. Fonte provides an example: "Earthworms increase soil porosity, which assists in the beneficial capture and retention of water."

It advocates better management of soil biology to improve agricultural productivity and reduce dependence on agrochemicals. "Soils are still a huge black box that we don't fully understand," Fonte admits. "This work helps show that there are many opportunities that we are simply ignoring," he adds.

"There are probably other soil organisms that are even more important, especially microbial communities," Fonte concludes.

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