Industrial agricultural plantations are a rapidly increasing yet largely unmeasured source of tropical land cover change. Here, we evaluate impacts of oil palm plantation development on land cover, carbon flux, and agrarian community lands in West Kalimantan, Indonesian Borneo. With a spatially explicit land change/carbon bookkeeping model, parameterized using high-resolution satellite time series and informed by socioeconomic surveys, we assess previous and project future plantation expansion under five scenarios. Although fire was the primary proximate cause of 1989-2008 deforestation (93%) and net carbon emissions (69%), by 2007-2008, oil palm directly caused 27% of total and 40% of peatland deforestation. Plantation land sources exhibited distinctive temporal dynamics, comprising 81% forests on mineral soils (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001), shifting to 69% peatlands (2008)(2009)(2010)(2011). Plantation leases reveal vast development potential. In 2008, leases spanned ∼65% of the region, including 62% on peatlands and 59% of community-managed lands, yet <10% of lease area was planted. Projecting business as usual (BAU), by 2020 ∼40% of regional and 35% of community lands are cleared for oil palm, generating 26% of net carbon emissions. Intact forest cover declines to 4%, and the proportion of emissions sourced from peatlands increases 38%. Prohibiting intact and logged forest and peatland conversion to oil palm reduces emissions only 4% below BAU, because of continued uncontrolled fire. Protecting logged forests achieves greater carbon emissions reductions (21%) than protecting intact forests alone (9%) and is critical for mitigating carbon emissions. Extensive allocated leases constrain land management options, requiring trade-offs among oil palm production, carbon emissions mitigation, and maintaining community landholdings.greenhouse gas emissions | agribusiness | Elaeis guineensis | moratorium | REDD+ G lobal demand for food, biofuels, and natural resources drives capitalized agricultural development, especially for tropical plantations (1-4). Forest and peatland conversion to plantation agriculture may be a substantial source of greenhouse gas (GHG) emissions from land cover change (5, 6), which generates 10-20% of net global GHG emissions (7). By acquiring extensive arable lands, plantations also affect land availability for smallholder farmers and communities, potentially altering local livelihood options (8, 9). Whereas environmental degradation from tropical agribusiness may overwhelm benefits of high-yield plantations for world food security (6, 10), impacts on carbon (C) flux and livelihoods are highly uncertain because locations and land sources for plantations remain largely undocumented.Complex processes of land acquisition and plantation development unfold across heterogeneous biophysical and sociopolitical landscapes in both time and space. Land cover histories constrain present land use and potential outcomes from agribusiness expansion (11). Discerning the land cover traje...
