Abstract
Strong international demand for natural rubber is driving expansion of industrial-scale and smallholder monoculture plantations, with >2 million ha established during the last decade. Mainland Southeast Asia and Southwest China represent the epicenter of rapid rubber expansion; here we review impacts on forest ecosystems and biodiversity. We estimate that 4.3–8.5 million ha of additional rubber plantations are required to meet projected demand by 2024, threatening significant areas of Asian forest, including many protected areas. Uncertainties concern the potential for yield intensification of existing cultivation to mitigate demand for new rubber area, versus potential displacement of rubber by more profitable oil palm. Our review of available studies indicates that conversion of forests or swidden agriculture to monoculture rubber negatively impacts bird, bat and invertebrate biodiversity. However, rubber agroforests in some areas of Southeast Asia support a subset of forest biodiversity in landscapes that retain little natural forest. Work is urgently needed to: improve understanding of whether land-sparing or land-sharing rubber cultivation will best serve biodiversity conservation, investigate the potential to accommodate biodiversity within existing rubber-dominated landscapes while maintaining yields, and ensure rigorous biodiversity and social standards via the development of a sustainability initiative.
Highlights
Tropical forest loss is increasing (Hansen et al 2013), primarily due to agricultural expansion (Gibbs et al 2010; Foley et al 2011)
We summarize the history of rubber expansion and land-use change, contrasting the contexts across Southeast Asia, between insular (Sabah, Sarawak, and Indonesia) and mainland areas
We explore four scenarios for Southeast Asia: 1a, Basic: retention of existing rubber cultivation at current yields without intensification or further displacement, with future demand met by expansion at yields of modern plantations in mainland Southeast Asia (0.915– 1.452 t ha−1 year−1, Appendix S1)
Summary
Tropical forest loss is increasing (Hansen et al 2013), primarily due to agricultural expansion (Gibbs et al 2010; Foley et al 2011). Concern over expansion of agroindustrial tree plantations in the tropics, including oil palm (Fitzherbert et al 2008; Koh & Wilcove 2008) and paper-pulp (Wilcove et al 2013), led to a series of sustainability labels developed to reduce negative biodiversity, ecosystem service and social outcomes (Edwards & Laurance 2012; Edwards et al 2012). We estimate potential future rubber extent, and collate evidence for biodiversity impacts of rubber cultivation from across Southeast Asia, to inform emerging sustainability labeling efforts by the rubber industry and focus further research on this rapidly expanding crop. Conservation Letters, xxx 2015, 00(00), 1–13 Copyright and Photocopying: C 2015 The Authors Conservation Letters published by Wiley
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