They are famous for their usefulness in the garden and in the field. But how much do the world’s earthworms actually contribute to agricultural yields? Researchers have now investigated this question quantitatively for the first time. According to their extensive data analysis, more than 140 million tons of global food production can be attributed to earthworm activity. Specifically, they contribute 6.5 percent to the yield of grains and 2.3 percent of legumes. The results underline the importance of protecting and promoting the valuable beneficial organisms, say the scientists.
Worms are actually rather unpopular creatures – but there is one exception: Earthworms are considered important beneficial organisms for humans – and rightly so, because they have been proven to contribute to soil fertility in a variety of ways. Basically, by converting organic matter in the soil, they play an important role in material cycles and the continued provision of plant nutrients. They also loosen the soil through their digging work, thereby promoting root growth and increasing water storage capacity. Studies have also shown more subtle positive effects: earthworms promote the development of other useful soil organisms, stimulate favorable hormone production in plants and protect them from pathogens.
Useful – but how specific?
In principle, the positive effect of earthworms is already well documented and there are even quantitative assessments of their contribution to overall productivity in certain crops. But so far these findings have not been projected onto agricultural production on a large scale. Researchers led by Steven Fonte from Colorado State University in Fort Collins have now closed this gap. “To our knowledge, this is the first scientific study to look at a specific representative of soil biodiversity in order to examine the value of this entity to us on a global scale,” says Fonte.
For their study, the scientists collected data on the distribution and abundance of earthworms in agricultural areas of the world. In addition, various other information such as soil characteristics and crop yields in the respective regions were included in their calculations. Based on the known positive effects on the productivity of crops, the team then developed projections to estimate the overall impact of the earthworms. The researchers concentrated on particularly important crops: for cereals, these were rice, corn, wheat and barley. The focus was also on legumes, which included soybeans, peas, chickpeas and lentils.
Great importance documented
As the team reports, their calculations showed that, globally, the beneficial effects of earthworms are responsible for around 6.5 percent of grain production and 2.3 percent of legume production. In total, this corresponds to food production of over 140 million tons per year, the calculations showed. In detail, it was shown that earthworms are more important in the global south than in the north: in sub-Saharan Africa they even contribute ten percent of the grain yield and in Latin America they contribute eight percent.
As the scientists explain, this has to do with the fact that fewer artificial fertilizers and pesticides tend to be used in these regions. Instead, organic materials such as crop residues, which are converted into the soil by earthworms, are used to supply the plants with nutrients. This in turn has positive effects on plant health.
“Our results highlight that earthworms are an important driver of global food production and that investments in agroecological strategies to support earthworm populations could make a major contribution to sustainable agricultural goals,” the scientists write. They also emphasize that the beneficial organisms can mitigate the effects of droughts, which are expected to become more frequent in the future as a result of climate change. Through their burrowing activity, earthworms promote the porosity of the soil, which helps to better absorb and store water.
Fonte and his colleagues now hope that their study can encourage other scientists to research the importance of soil organisms for plant growth in more detail. In addition to the earthworm, other underground inhabitants can also play an important role. Fonte concludes: “Soils are still this big, big black box that we don’t fully understand.”
Source: Colorado State University, specialist article: Nature Communications, doi: 10.1038/s41467-023-41286-7