The era of Mongol Yuan domination of Korea, from 1271 to 1368, lasted less than a century. The relatively short span, however, would witness the integration of the Korean peninsula into the Mongol imperial ecumene, with immense implications for the late Koryŏ (918-1392) and subsequent Chosŏn (1392-1910) dynasties. Yuan exploitation of Korean coastal forests forced later Koryŏ and particularly early Chosŏn officials to reckon with the limited supply of domestic timber. Timber shortages, perceived and real, would compel early Chosŏn bureaucrats to establish one of the longest-lasting state forestry systems of the pre-industrial world. Yuan reliance on horse cavalry necessitated the establishment of ranches on southwestern islands and along the coast; in turn, they would form the basis for the expansion of state ranches for military use in the early Chosŏn era. By extracting new flows of sylvan resources from the peninsula and instituting new mechanisms for corralling animal resources, the Mongol empire established the basis from which the Chosŏn dynasty would launch centralized control of the peninsula’s flora and fauna. The Mongol environmental legacy, moreover, would linger for centuries in pine forests and horse ranches across Korea’s coasts and islands. This paper thus posits a fuller inquiry into the largely unexplored environmental legacies left by the largest land empire in world history. Moreover, I invite more discussion into the long-term environmental imprints that result from interactions between sedentary and nomadic states and the by-play between equine and sylvan ecologies and institutions.