International market forces have played an increasingly important role in shaping land use dynamics through complex supply chains. In Costa Rica, the shift from a net loss to a net gain in forest cover was facilitated by forest plantations and the replacement of extensive cropland and pastures by export-oriented, high-yielding crops. However, agricultural intensification generated several feedbacks affecting forests. We analyzed the interactions between Costa Rica’s agricultural and forestry sectors associated with the use of wood pallets for commodity exports over 1985–2013. Wood pallets for growing agricultural exports created a demand for domestic tree plantations. The annual land demand for tree plantations to produce these wood pallets increased by 669%, reaching 17,606 ha in 2013 and representing 28% of the increase in demand for cropland for agricultural exports over 1994–2013. Wood supplied from plantations failed to fully substitute for wood from natural forests, only allowing for a relative substitution and preventing a major sparing of these forests. The dominant use of wood from plantations for production of low-value pallets de-incentivized investments in sustainable plantations. We showed that, beyond the typical interactions between agriculture and forestry through direct competition for land, international trade generated unexpected feedback where agricultural activities and supply chains affected forestry by triggering new demand and profound changes in forestry management. Land systems behave as complex systems, calling for integrated approaches to study the outcomes of forest conservation, reforestation programs, and development of land-based businesses.