Carbon emissions from forest conversion by Kalimantan oil palm plantations

Oil palm supplies >30% of world vegetable oil production1. Plantation expansion is occurring throughout the tropics, predominantly in Indonesia, where forests with heterogeneous carbon stocks undergo high conversion rates2–4. Quantifying oil palm’s contribution to global carbon budgets therefore requires refined spatio-temporal assessments of land cover converted to plantations5,6. Here, we report oil palm development across Kalimantan (538,346 km2) from 1990 to 2010, and project expansion to 2020 within government-allocated leases. Using Landsat satellite analyses to discern multiple land covers, coupled with aboveand below-ground carbon accounting, we develop the first high-resolution carbon flux estimates from Kalimantan plantations. From 1990 to 2010, 90% of lands converted to oil palm were forested (47% intact, 22% logged, 21% agroforests). By 2010, 87% of total oil palm area (31,640 km2) occurred on mineral soils, and these plantations contributed 65–75% of 1990–2010 net oil palm emissions (0.020–0.024 GtC yr−1). Although oil palm expanded 278% from 2000 to 2010, 79% of allocated leases remained undeveloped. By 2020, full lease development would convert 93, 844 km2 (∼90% forested lands, including 41% intact forests). Oil palm would then occupy 34% of lowlands outside protected areas. Plantation expansion in Kalimantan alone is projected to contribute 18–22% (0.12–0.15 GtC yr−1) of Indonesia’s 2020 CO2-equivalent emissions. Allocated oil palm leases represent a critical yet undocumented source of deforestation and carbon emissions. Oil palm (Elaeis guineensis) plantations in Sumatra and Kalimantan produce∼50% of palm oil worldwide1, and Indonesia plans to double national palm oil production primarily by expanding landholdings in Kalimantan and Papua7. In 2010, Indonesian palm oil and palm kernel oil production generated ∼US$11.1 billion (ref. 1). Yet, Indonesia ranks among the top national greenhouse-gas (GHG) emitters, largely from land-based carbon emissions including deforestation and forest degradation8. Although fires are the dominant cause of Indonesia’s emissions during droughts9, oil palm’s contribution to deforestation and emissions is uncertain. Over 50% of oil palmwas planted from 2000 to 2010 (ref. 10), yet automated analysis of remote-sensing products has proved insufficient to detect young (<10 yr) or small-scale (<200 ha) oil palm agriculture11,12. Recently developed plantations remain undocumented across mineral soils13, which comprise 88%