Guano de isla has long served as a crucial organic fertilizer for vulnerable smallholder farmers in Peru, yet its availability is under severe threat. Ecological disruptions, including avian influenza outbreaks and strong climate events, have caused catastrophic declines in seabird populations, plummeting numbers from four million down to fractions of a million. This dramatic reduction creates an urgent agricultural challenge, as traditional organic stockpiles are finite and future shortages threaten the livelihoods of rural communities who depend on state-subsidized access to this natural resource. Without intervention, the impending scarcity of seabird guano risks destabilizing food security and agricultural productivity across the region.

To address this challenge, researchers evaluated whether adding biochar to sandy soils could enhance nutrient retention and uptake, compensating for lower fertilizer inputs. Conducting field trials on lettuce cultivation in Lurín, Peru, the team tested various combinations of soil amendments. Biochar, produced from municipal green waste, features a highly porous structure and a large surface area that prevents essential nutrients like nitrogen and potassium from washing away through porous sandy ground. By holding these nutrients safely within the root zone, the carbon-rich amendment enables plants to absorb fertilizers much more effectively even when application quantities are substantially decreased.

The experimental results demonstrated that plots treated with biochar combined with a fifty percent reduction in seabird guano achieved crop yields statistically equivalent to plots receiving the full, unreduced fertilizer rate. Furthermore, economic evaluations highlighted that while conventional market conditions yield low financial returns, transitioning to organic markets transforms the strategy into a highly lucrative enterprise. The combination of biochar and reduced guano reached a maximum value-cost ratio of 12.9 when organic price premiums were paired with biochar production costs offset by carbon credits. Ultimately, this integrative practice offers a sustainable, nature-based pathway to conserve scarce natural fertilizers, protect vulnerable farming communities, and enhance climate resilience across the Global South.

Source: Espejo, S. E. L., De La Cruz, R. C. C., Loret de Mola León, U., Carruitero, J. L. M., Zavalaga, C., & Ladd, B. (2026). Biochar enhances the use efficiency of guano de isla and could boost profitability and food security for smallholders in the global south. Discover Life, 56, 22.