Latest 30-m map of mature rubber plantations in Mainland Southeast Asia and Yunnan province of China: Spatial patterns and geographical characteristics

Abstract

Knowledge of the location, area and extent of rubber plantations is a prerequisite for assessing their ecological and environmental impacts. Mainland Southeast Asia (MSEA) and Yunnan province (MSEA&YN) in China are globally important rubber-planting regions. Rubber cultivation in areas at moderate and low altitudes (<1000 m) within these regions has expanded rapidly in recent years. However, datasets of maps generated at a fine spatial resolution are still unavailable for MSEA&YN. Because of this, three relevant and important questions remain unanswered: what are the northernmost boundary for rubber production in these regions, what is the highest altitude at which rubber is produced, and how are the plantations distributed in (cross-) border regions? An approach of the phenology- and Landsat-based re-normalized vegetation index (RNVI), originally developed for Xishuangbanna in southern China, is used in this study to verify the feasibility of mapping mature rubber plantations in MSEA&YN using the Landsat 8 Operational Land Imager data products acquired from January to April, 2013 to 2018. Characteristics of the vertical and horizontal distributions of mature rubber plantations in MSEA&YN, as well as national differences especially in the (cross-) borders, were examined using the generated map. The results showed that the RNVI method, although tailored to the northern edge of the tropics, is useful for detecting mature rubber plantations in MSEA&YN. The latest map of mature rubber plantations indicated that they occupied a total area of 7.69 × 106 ha, accounting for 3.32% of the study area. Spatial analyses showed three typical features of the distribution: new plantations at higher (over 1000 m) and lower (below 200 m) elevations, more cultivation in the borderlands (over a half within 60 km buffers), and their northward movement (as far as 25°N). The results of this study have important implications for phenological methods verification in the tropics, and provide valuable information on mature rubber plantations in MSEA&YN.