Where Soil Carbon Meets Life: A Keynote Perspective on Earthworms and Agroecosystem Biodiversity
Biodiversity is increasingly recognized as a core driver of agronomic performance and climate resilience across agroecosystems. Once viewed as an environmental add-on at the margins of farming systems, it is now understood to be central to how soils function, crops grow, and landscapes remain productive over time.
Last month, we spoke with Dr. Rattan Lal, Distinguished Professor of Soil Science and Founder and Director of the CFAES Rattan Lal Center for Carbon Management and Sequestration at the Ohio State University, about his decades of research on soil organic carbon as a foundation for soil health—and the essential role earthworms play in that system. While biodiversity in agricultural systems spans everything from microbes to birds and pollinators, this article zooms in on earthworms as a tangible entry point to agricultural biodiversity.
Lessons from Tropical Soils
Early in his career, Dr. Lal spent 17 years conducting soil research and field trials in Nigeria at the International Institute of Tropical Agriculture. Working in tropical systems highly vulnerable to degradation, his research demonstrated that increasing soil organic farming through regenerative agricultural practices like using cover crops, no-till, manure, and mulching can counteract rapid soil degradation.
One of the most striking findings from this work was that when soil organic carbon levels fall below approximately 0.5%, fertilizer becomes less effective and can also be harmful, because plants can no longer efficiently absorb nutrients. In long-term trials where crop residue was removed for 15 years on the Nigerian plots, soils became less productive and deficit in activity and in soil biota species diversity (especially that of earthworms). These experiments highlighted a clear conclusion: restoring soil organic matter is essential for soil health and food security, particularly in regions facing intense biotic and abiotic stress. Drawing on decades of work in soils of the tropics, Dr Lal challenges the tendency to view soil carbon as a superficial metric. Instead, he urges a focus on what soil carbon sustains beneath the surface: the vast community of soil organisms—the “beating heart” of healthy soils. His work invites us to rethink agroecosystem health not as a function of inputs alone, but as the outcome of interconnected life working together across the system. In this type of system, soils are healthy, disease suppressive, sustain high productivity, and provide many ecosystem services.
Earthworms as Engineers of Soil Health
As a soil physicist, Dr. Lal studied earthworms as an indicator of soil biodiversity. His research showed that the Nigerian fields managed with a focus on soil health and using regenerative practices supported significantly higher earthworm populations than fields where crop residue was removed.
Earthworms function as natural soil engineers. Their tunneling improves aeration and drainage, while their movement mixes organic matter with mineral soil to produce nutrient-rich castings. These physical changes enhance microbial activity, improve soil structure, and increase nutrient availability for plants, ultimately boosting crop productivity.
Charles Darwin recognized their importance more than a century ago, dedicating his final book, The Formation of Vegetable Mould through the Action of Worms (1881), to their influence on soil fertility. He called earthworms the intestines of the earth.
Modern research continues to reinforce these early insights. Earthworms are increasingly described as a keystone species; organisms whose presence disproportionately influences ecosystem function relative to their abundance. Recent studies estimate that earthworms make a substantial contribution to global food production, underscoring their often-overlooked role in agricultural systems.
Regenerative Practices and Biodiversity Take Time
After his work in Nigeria, Dr. Lal continued his research in the United States, where he observed similar patterns. Regenerative agricultural practices consistently increased earthworm populations and overall soil biodiversity which also enhanced soil organic matter content in the root zone and helped in the adaptation and mitigation of climate change.
However, these changes do not happen overnight. Increases in soil carbon, soil health, and biodiversity require time, consistency, and long-term management, which creates a gap between when farmers adopt practices and when outcomes become measurable. This time lag is often cited as one of the biggest barriers to adoption despite strong scientific consensus on long-term benefits of regenerative practices.
Why Paying for Ecosystem Services Matters
This lag is precisely why paying farmers for ecosystem services such as biodiversity, water quality, and carbon sequestration makes sense. Farmers play a central role in generating and maintaining these public benefits, yet the social value of ecosystem services far exceeds what markets often pay. Supporting practice adoption through ecosystem service programs helps bridge that gap and recognizes farmers as stewards of environmental outcomes. Improving soil health is critical to agriculture’s role as an integral part of the solution to addressing global issues of the 21st Century and advancing the 2030 Agenda for Sustainable Development of the United Nation’s Sustainable Development Goals. Ecosystem service markets are not incentives for “new behavior,” but mechanisms to fairly compensate farmers for outcomes that society already depends on.
Measuring Biodiversity in Practice
At ESMC, we’ve developed a biodiversity module for our EcoHarvest program that measures in-field biodiversity outcomes based on regenerative practices such as those highlighted by Dr. Lal. This approach reflects a growing consensus that biodiversity assessment must combine both practice-based indicators and outcome-based signals to be credible and scalable. The module accounts for improved habitat for pollinators, insects, and birds, as well as increased biodiversity in the soil biome where earthworms play a key role.
Because there is currently no comprehensive public database for earthworm populations, their presence is not required as a standard input. However, when producers or partners can provide direct evidence, such as field observations or soil test data, this information can be credited as an additional functional contribution, increasing the total biodiversity outcome rather than limiting participation. This flexibility reflects a broader movement in soil-health science toward a simple principle: measure what we can, and don’t exclude what we can’t. Additionally, to help overcome existing gaps in public data on soil organisms and other biodiversity indicators, ESMC is actively building its own growing database of key species. This database expands each year as the biodiversity module is applied to new fields and acres across different ecoregions, allowing species information to accumulate over time and improving our ability to capture regionally relevant biodiversity outcomes as programs scale.
Soil organic carbon feeds biodiversity, biodiversity sustains function, and different functional groups of organisms including soil bioturbators like earthworms, can signal when that system is working. Their presence reflects years of management, patience, and care. These outcomes cannot be rushed but can be supported. By recognizing and rewarding the ecosystem services farmers produce, we create the conditions for healthier soils, more resilient agriculture, and landscapes that continue to work for both people and the planet.
