LB 1-6 - Understanding the potential contribution of earthworms to global food production

Background/Question/Methods:

Intensification of agriculture in the last century has produced abundant food but has come at a significant environmental cost (e.g., pollutions, biodiversity loss, climate change). These problems are only expected to worsen with increasing global food demand, thus emphasizing the need for more agroecological approaches to produce our food. Improved management of soil biological communities offers great potential to support food production and multiple ecosystem services. Earthworms are important ecosystem engineers that can enhance productivity, via effects on nutrient turnover and other soil processes. Despite their widespread recognition as indicators and purveyors of healthy soils, the potential contribution of earthworms and other beneficial soil organisms to agricultural production remains poorly understood.

To address this knowledge gap, we estimated earthworm impacts on crop productivity using mean effect sizes from a previous meta-analysis that reported earthworm impacts on different crop types, and under different soil properties (texture, pH), N fertilizer inputs, as well as at different levels of earthworm abundance. These values were combined with a recent global map on the distribution and abundance of earthworms, together with global soil, management, and crop data layers to estimate the potential contribution of earthworms to agricultural production at a global scale.

Results/Conclusions:

Our preliminary results suggest that earthworms may contribute to roughly 5.7% of crop yield globally. We estimate the production of grains (maize, rice, wheat, barley) to increase by more than 7% due to the presence of earthworms, equivalent to roughly 150 million tons of food annually, while legumes benefit relatively less, showing a 3.4 % increase, or 25 million tons. The potential contribution of earthworms to agricultural production becomes especially notable in the global South. For example, we estimate earthworms to contribute to a 19% increase in total grain yield in Sub-Saharan Africa and a 12% increase in Latin America. This compares with estimated earthworm contributions to grain yield of just 9% in North America and 6% in Europe. This discrepancy is likely due to higher fertilizer inputs in the global North, which partially negates earthworm benefits to soil nutrient availability. Given that earthworm populations are understudied in many regions (and potentially underestimated), we suspect that our approach may undervalue the global contribution of earthworms to food production. While we recognize that our approach involves many sources of potential error, we believe this knowledge holds considerable value for informing the development of new agroecological practices and policies.