Assessing drone-based direct seeding with bare and encapsulated seeds for enriching degraded tropical forest fragments

Restoring degraded forest fragments often requires reintroducing native tree species lost through disturbances including logging, fire, and fragmentation, yet the operational and financial feasibility of this intervention remains a barrier. We evaluated the ecological and economic feasibility of drone-based seeding of encapsulated and non-encapsulated (bare) seeds in degraded fragments in the Brazilian Atlantic Forest. Seeds were encapsulated in cassava starch capsules containing hydrogel, fertilized organic substrate, and mycorrhizal fungi. Twenty native tree species were sown by drones (35,926 seeds ha −1 ) into two degraded fragments. Seedling emergence, survival, and establishment were monitored for 12 months. Encapsulated seeds germinated faster and produced more seedlings than bare seeds during the first month (2891 vs. 1605 seedlings ha −1 ). However, high post-emergence mortality, likely driven by capsule components inducing premature germination misaligned with favorable environmental conditions, offset this early advantage. After one year, bare seeds had higher establishment (4.14%, 1487 seedlings ha −1 vs. 2.19%, 787 seedlings ha −1 ) and lower cost per established seedling (USD 0.44 vs. USD 3.87) than encapsulated seeds. Drone operation was highly efficient for bare seeds, with one hectare sown in ∼6.9 min in a single flight. Conversely, the greater volume of encapsulated seeds required multiple flights, totaling 16.4 min ha −1 of flight time, excluding tank refilling. Bare seeds outperformed encapsulated seeds in establishment, cost-effectiveness, and operational efficiency. Further studies are needed to assess longer-term tree recruitment and to test different capsule formulations and sizes. Nevertheless, the operational feasibility and cost-effectiveness for bare seeds suggest that drone-based seeding is promising for enriching degraded forests.